Engine Tune-Up PDF

1 1.1 Purpose of Engine Tune-up ―Tune-up‖ means checking all phases of engine operation and making any adjustments, repairs and replacements required for the engine auxiliaries and accessories to conform to the car manufacturers‘ specifications. Tuning an engine does not mean rebuilding or performi...

1 1.1 Purpose of Engine Tune-up ―Tune-up‖ means checking all phases of engine operation and making any adjustments, repairs and replacements required for the engine auxiliaries and accessories to conform to the car manufacturers‘ specifications. Tuning an engine does not mean rebuilding or performing repair operations on the engine itself even though these may be required. However checkup operations which are a part of every tune- up job may reveal serious engine defects which require corrective measures. It is as essential to check engine operation after adjustments are made as it is to test before doing corrective work. The only assurance of a corrective adjustment is a double check after work has been completed. Trying to tune on engine that has poor bearings, rings, pistons or valves is difficult if not impossible. Tune-up as it will be used here means re-establishing original factory specifications as nearly as possible. An automotive tune-up is an orderly process of inspection, diagnosis, testing, and adjustment that is periodically necessary to maintain peak engine performance or restore the engine to original operating efficiency. The three fundamental divisions of tune-up procedure can also be considered as: 1. The engine 2. Electrical system 3. The fuel system These three designations cover the same items as the terms compression, ignition and carburetion. The tune-up man must first detect the faulty parts and units whose deterioration is affecting the proper functioning of the engine. He must then report engine faults and correct defects of auxiliary units by adjustment, repair, or replacement, restoring the units as near to their original condition as possible. Diagnosis of the engine and its auxiliary systems is an important element of tune-up, since without knowing what is needed; it is difficult to know what should be done. A good tune-up job, therefore, consists of two parts. 1. Diagnosis, analysis or troubleshooting  2. Correction, which may be adjustment, replacement or repair 1.2 Troubleshooting Principles The following sections are a method, or checklist, to help you troubleshoot engine performance problems. 1. Ask the Driver Even if an owner brings you a car for routine maintenance (change oil, filters, spark plugs, and so on), he or she may have a general complaint about performance or a vague idea that, ―It‘s not running the way it should.‖  Ask the driver about specific problems.  Also ask about overall performance. Even a general answer such as,  ―Well, sometimes it‘s hard to start,‖ or  ―Mileage isn‘t too good,‖ can be a helpful clue for your testing. If the car has a specific problem, it‘s helpful to talk to the person who was driving when it occurred. Ask questions such as:  Does the problem occur at specific times or temperatures – idle, cruising, acceleration, at night with heavy electrical loads, cold starting, hot starting, or any combination?  Does the problem occur regularly or at random?  What are all the symptoms – noises, smells, vibrations, or combination of signs?  Has the problem occurred before and what was done to fix it?  When was the car last serviced, and what was done then? Many large shops have service writers who prepare work orders and get information from customers. If you can‘t talk to the owner directly, read the work order carefully and ask the service writer for details. 2. Ask the Car Equally important, drive the car and check performance for yourself. The owner may complain about a rough idle and never notice the mushy automatic transmission shifting and slight high – speed surge caused by the same vacuum leak. Combined clues that lead to a single cause can save you time. Also, by driving the car to analyze the owner‘s comments, you will get an idea of what the owner expects in the way of drivability. A ―hard – starting‖ problem may occur because the driver does not follow specific starting instructions for the vehicle. You may operate the car immediately or later during your testing. You may have to let it cool down to check a cold – engine problem. When you do drive it, observe the symptom carefully to be sure when it does occur and when it doesn‘t. If the problem is a ―rough idle,‖ does it happen with the engine hot or cold, or both? Does it happen with the air conditioner on or off, or both? Does the car overheat? Does it smoke? Are there other related symptoms? 3. Know the Car, Know the Specifications Before you start troubleshooting, be sure you know what you are working on. That sounds simple, but the same type of vehicle can have different engines. It can have different transmissions. It may or may not have air conditioning. It may be designed for different countries with specific differences. Start to identify the car by checking the vehicle identification number on the VIN plate. Then check the engine ―emission control‖ decal for basic specifications, such as timing, idle speed, and spark plug gap. The engine decal also has summary instructions for idle and timing adjustments and, along with other calibration labels, will identify a car with running changes made during the model year. The VIN and engine decals will lead you to detailed specifications and procedures in reference manuals. You also may need electrical and vacuum diagrams. Look them up, using the VIN and engine decal numbers. Most cars have a decal under the hood that shows engine vacuum hose connections. 4. Identify the Possible Causes and Cures You actually start this step when you learn the owner‘s complaint, and you continue identifying and eliminating causes until you finish the job. Make a list, in your head or on paper, of the symptoms and possible causes. Then check the possibilities one at a time. Begin with the simplest. Don‘t condemn an alternator for a low – voltage problem without checking for a loose drive belt first. 5. Test from the General to the Specific Testing is a process of elimination. If you immediately look for the cause of a rough idle in the ignition system, you eliminate other possible causes in the fuel and emission systems without checking them. To isolate a problem accurately, you must begin by checking general engine condition and performance. Then, test each system – fuel, electrical, emission – for overall operation. Finally, check individual components. Start by general tests of overall system operation which are also called area tests. These tests allow you to narrow down the cause of a problem. Detailed, or pinpoint tests, then allow you to isolate a bad component. Carmakers follow the same principle with their test procedures. 6. Know the System, Isolate the Problem Suppose the driver‘s complaint is a rough acceleration when cold, and you‘re testing shows that the exhaust gas recirculation (EGR) valve is opening when it should not. You then must ask yourself, ―Why?‖ Is vacuum to the valve controlled by a coolant temperature vacuum valve or by a solenoid? If a solenoid is used, how is it switched, by a coolant switch or an engine computer? Is the EGR valve broken and stuck open? To isolate the problem, you must know what parts are in the system and how they work. This is another way to identify possible causes. The EGR valve may open at the wrong time because of:  A mechanical problem – broken valve  A wrong electric signal to a solenoid  A broken coolant temperature sensor  A cooling system problem – over – heating  Incorrect vacuum hose connections 7. Test Logically and Systematically Now that you have isolated the problem to one system, you can use vacuum diagrams to determine hose connections and vacuum sources. Use electrical diagrams to determine the power source, the ground connection, and how a solenoid is energized. You can determine when vacuum should and should not be present at the valve and when a solenoid should be energized and de-energized. If engine roughness occurs only on cold acceleration, the problem probably is not a bad EGR valve. If the valve were stuck open, performance also would suffer at hot and cold idle and at full throttle. If you find vacuum at the valve as you accelerate a cold engine, you must check the vacuum control devices. If a solenoid is energized to open a vacuum valve, check for voltage at the solenoid. If voltage is not present, but the solenoid valve is open, you probably have a bad solenoid. If voltage is present when it should not be, you must check the electrical circuit. Check the electrical diagram and manufacturer‘s test procedures to trace voltage to the source. 8. Double-check Your Test Results Suppose your tests in step 7 seem to show that a vacuum solenoid is permanently grounded and energized. The specific cause could be:  A ground inside the solenoid  A grounded wire between the switch and the solenoid  A defective switch  An overheating engine that closes the switch too soon Disconnect the switch wire, first at the solenoid and then at the switch, to see if the solenoid stays energized. Check for voltage and short circuits to ground at the solenoid, in the wire, and at the switch. Check the switch itself to see if it is closing when it should not. The important principle, whether you are testing electrical, vacuum, hydraulic, or mechanical systems, is to test systematically from one point to another and double-check your results before making repairs. You often work with several systems – vacuum and electrical, for example – to isolate a problem. The symptom may come from a vacuum component, but the final cause may be an electrical fault. 9. Repair and Retest Suppose your results in steps 7 and 8 show that the coolant switch is bad. Replace the switch and reconnect and check all vacuum and electrical connections in the system. Then, retest the complete system. Be sure the EGR valve opens only when it should and that the switch and solenoid work properly. Most importantly, be sure you have cured the original ―roughness on cold acceleration‖ problem. You may have replaced one bad part and eliminated a problem in one system. But if you haven‘t corrected the owner‘s original complaint, you haven‘t finished the job. If the roughness still exists, there is another problem, or problems, in another system that you must find and fix, using these same steps. 1.2.1 Gasoline Engine Trouble Diagnosis Chart Table1: 1 Gasoline Trouble diagnosis Chart Complaint Possible Cause Check or Correction  Run-down battery  Recharge or replace battery;  Starting circuit open start engine with jumper  Starting-motor drive jammed battery and cables.  Starting motor jammed  Find and eliminate the open;  Engine jammed check for dirty or loose cables.  Transmission not in neutral or  Remove starting motor and Engine will not crank neutral switch out of adjustment. free drive  Seat belt not fastened or interlock  Remove starting motor for faulty disassembly and repair.  See also causes listed under item 3;  Check engine to find trouble. driver may have run battery down  Check and adjust neutral trying to start. switch if necessary  Check interlock.  Partly discharged battery  Recharge or replace battery;  Defective starting motor start engine with jumper Engine cranks slowly  Bad connections in starting circuit battery and cables. but will not start  Repair or replace  Check for undersize, loose, or dirty cables; replace or clean and tighten.  Defective ignition system  Try spark test; check timing,  Defective fuel pump or over- ignition system Engine cranks at choking  Prime engine, check normal speed but will  Air leaks in intake manifold or accelerator pump discharge, not start carburetor fuel line, choke, carburetor  Defect in engine  Tighten mounting; replace  Ignition coil or resistor burned out gaskets as needed  Plugged fuel filter  Check compression or  Complaint Possible Cause Check or Correction  Plugged or collapsed exhaust leakage, valve action, timing system  Replace  Clean or replace  Replace collapsed parts  Defective spark plug  Clean or replace  Defective distributor cap or spark  Replace plug cable  Free valve; service valve  Valve stuck open guide  Broken valve spring  Replace Engine runs but  Burned valve  Replace misses: one cylinder  Bent pushrod  Replace  Flat cam lobe  Replace camshaft  Defective piston or rings  Replace; service cylinder wall  Defective head gasket as necessary  Intake – manifold leak  Replace  Replace gasket; tighten manifold bolts  Defective distributor advance, coil,  Check distributor, coil, condenser condenser  Defective fuel system  Check fuel pump, flex line,  Cross-firing plug wires carburetor  Loss of compression  Replace or relocate  Defective valve action  Check compression or leakage Engine runs but misses:  Worn pistons and rings  Check compression, leakage, different cylinders.  Overheated engine vacuum  Manifold heat-control valve stuck  Check compression, leakage,  Restricted exhaust vacuum  Check cooling system  Free valve  Check exhaust, tail pipe and muffler, eliminate restriction.  Complaint Possible Cause Check or Correction  Defective ignition  Check timing, distributor,  Defective fuel system wiring, condenser, coil, and  Secondary throttle valve not plugs opening fully  Check carburetor, choke,  Restricted exhaust filter, air cleaner, and fuel  Loss of compression pump.  Excessive carbon in engine  Adjust linkage  Defective valve action  Check tail pipe and muffler; Engine lacks power, eliminate restriction acceleration, or high  Check compression leakage speed performance:  Excessive rolling resistance from  Service engine hot or cold low tires, dragging brakes, wheel  Check with compression, misalignment, etc. leakage, vacuum testers  Heavy oil  Correct the defect causing  Wrong or bad fuel rolling resistance  Transmission not downshifting, or  Use correct oil defective torque converter  Use correct octane fuel  See also item 6 in Diesel Fuel-  Check transmission Injection-system Trouble- Diagnosis Engine lacks power,  Engine overheads  Check cooling system acceleration, or high  Choke stuck partly open  Repair or replace speed performance:  Sticking manifold heat-control  Free valve hot only valve  Use different fuel or shield  Vapor lock fuel line  Automatic choke stuck open  Repair or replace Engine lacks power,  Manifold heat-control valve stuck  Free valve acceleration, or high open  Repair or replace speed performance:  Cooling-system thermostat stuck  Free valves; service valve cold only open stems and guide as needed  Engine valves stuck open  Complaint Possible Cause Check or Correction  Lack of coolant  Add coolant; check for leak  Ignition timing late  Adjust timing  Loose or broken fan belt  Tighten or replace  Thermostat stuck closed  Replace  Clogged water jackets or radiator  Flush and clear core  Replace  Defective radiator hose  Repair or replace Engine overheats  Defective water pump  Add oil  Insufficient oil  Drive more slowly; keep  High-altitude, hot-climate radiator filled operation  Replace  Defective clutch  Retime, adjust or replace  Valve timing late; slack timing  TCS system or distributor chain has allowed chain to jump a defective tooth  No vacuum advance in any gear  Incorrect idle adjustment  Readjust idle mixture and Engine idles roughly  PCV or EGR vale stuck open speed  See also other causes listed under  Replace items 6 to 8  Choke valve stuck closed or will  Open choke valve; free or not close repair automatic choke  Fuel not getting to or through  Check fuel pump, lines, carburetor filter, float and the systems Engine stalls cold or as  Manifold heat-control valve stuck  Free valve it warms up  Throttle solenoid improperly set  Adjust  Idling speed set too low  Increase idling speed to  PCV or EGR valve stuck open specified rpm  Damper in thermostatic air cleaner  Replace in cold-air mode stuck closed.  Free; repair or replace control motor  Complaint Possible Cause Check or Correction  Defective fuel pump  Repair or replace fuel pump Engine after  Overheating stalls  See item 9 idling or slow-speed  High carburetor float level  Adjust driving  Incorrect idling adjustment  Adjust  Malfunctioning PCV or EGR valve  Replace  Throttle solenoid improperly set  Adjust  Vapor lock  Use different fuel or shield  Carburetor venting or idle fuel line Engine stalls after high compensator valve defective  Check and repair speed driving  Engine overheats  See item 9  PCV or EGR valve stuck open  Replace  Improperly set idle solenoid  Adjust  Ignition timing off  Adjust timing  Spark plugs of wrong heat range  Install correct plugs  Excessively rich or lean mixture  Repair or readjust fuel  Engine overheats pump or carburetor  Carbon in engine  See item 9 Engine backfires  Valves hot or stuck  Clean  Cracked distributor cap  Adjust, free, clean; replace  Inoperative anti-backfire valve if bad  Cross-firing plug wires  Replace  Replace  Replace  Incorrect idle-solenoid adjustment  Adjust; fix solenoid  Engine overheats  See item 9 Engine run-on, or  Hot spots in cylinders  Check plugs, pistons, dieseling  Timing advanced cylinders for carbon; check  In diesel engine, could be due to valves for defects and faulty injection-pump solenoid not seating turning off fuel valve  Adjust  Complaint Possible Cause Check or Correction  Ignition miss  Check plugs, wiring, cap,  Incorrect ignition timing coil, etc  Carburetor troubles  Time ignition  Faulty air injection  Check choke, float level, Too much HC and CO  Defective TCS system idle mixture screw, etc, as in exhaust gas  Defective catalytic converters listen in item 20  Check pump, hoses, manifold  Check system  Replace converters or catalyst Smoky exhaust  Excessive oil consumption  See item 18  Excessively rich mixture  See item 20  Blue smoke  Steam in exhaust  Replace gasket; tighten  Black smoke cylinder-head bolts to  White smoke eliminate coolant leakage  See also item 8 in into combustion chambers. Diesel Fuel Injection system Trouble Diagnosis  External leaks  Correct seals; replace  Burning oil in combustion chamber gaskets  High-speed driving  Check valve-stem Excessive oil clearance, piston rings, consumption cylinder walls, rod bearings  Drive more slowly  Worn engine bearings  Replace  Engine overheating  See item 9 Low oil pressure  Oil dilution or foaming  Replace oil  Lubricating-system defects  Check oil lines, oil pump,  Complaint Possible Cause Check or Correction relief valve  Jackrabbit starts  Drive more reasonably  High-speed driving  Drive more slowly  Short-run operation  Drive longer distances  Excessive fuel-pump pressure or  Reduce pressure; repair pump leakage pump  Choke partly closed after warm-up  Open; repair automatic  Clogged air cleaner choke  High carburetor float level  Clean  Stuck metering rod or power piston  Adjust  Worn carburetor jets  Free and clean  Stuck metering rod or power piston  Replace  Idle too rich or too fast  Free  Stuck accelerator-pump check  Adjust Excessive fuel valve  Free consumption  Carburetor leaks  Replace gaskets; tighten  Cylinder not firing screws; etc  Automatic transmission slipping or  Check coil, condenser, not up shifting timing, plugs, contact  Loss of engine compression (worn points, wiring engine)  Check transmission  Defective valve action (worn  Check compression or camshaft, belt or chain slack, or leakage jumped tooth)  Check with compression,  Excessive rolling resistance from leakage, or vacuum tester low tires, dragging brakes, wheel  Correct the defects causing misalignment, etc. the rolling resistance  Clutch slippage  Adjust or repair Engine noises  Valve and lifter  Readjust valve clearance or 1. Regular clicking  Detonation due to low-octane fuel, replace noisy hydraulic 2. Ping load on carbon, advanced ignition timing, lifters  Complaint Possible Cause Check or Correction acceleration or causes listed under item 14  Use higher-octane fuel; 3. Light knock or pound  Worn connection-rod bearings or remove carbon; adjust with engine floating crankpin; misaligned rod; lack of ignition timing 4. Light, metallic oil  Replace bearings; service double knock usually  Worn or loose pin or lack of oil crankpins; replace rod; add most audible during  Worn rings, cylinder walls, low oil idle ring tension, or broken rings  Service pin and bushing; 5. Chattering or rattling  Piston slap due to worn pistons or add oil during acceleration walls, collapsed piston skirts,  Service walls; replace rings 6. Hollow, muffled bell- excessive clearance, misaligned  Replace or resize pistons; like sound (engine connecting rods, or lack of oil service walls; replace rods; cold)  Regular noise; worn main bearings; add oil 7. Dull, heavy, metallic irregular noise: worn thrust  Replace or service bearings knock under load or bearing knock on clutch and crankshaft acceleration, engagement or on hard  Tighten mounting especially when cold. acceleration. 8. Miscellaneous noises  Loosely mounted accessories: (rattles, etc) alternator, horn, oil pan, front 9. See also items 4,7 &8 bumper, water pump in diesel Fuel- Injection-System Trouble Diagnosis 1.3.1 Diesel Fuel-Injection System Trouble-Diagnosis Chart Table1: 2 Diesel Fuel-Injection System Trouble-Diagnosis Chart Complaint Possible Cause Check or Correction  Complaint Possible Cause Check or Correction  Incorrect or dirty fuel  Flush system-use correct fuel  No fuel to nozzle or  Check for fuel to nozzle Engine cranks injection pump  Check return, clean normally but will not  Plugged fuel return  Retime start  Pump timing off  Inoperative glow plugs, incorrect starting procedure, or internal engine problems  Fuel low in tank  Fill tank  Incorrect or dirty fuel  Flush system-use correct fuel  Limited fuel to nozzles or  Check for fuel to nozzles and to Engine starts but stalls injection pump pump on idle  Restricted fuel return  Check return, clean  Idle incorrectly set  Reset idle  Pump timing off  Retime  Injection-pump trouble  Install new pump  Internal engine problems  Low idle incorrect  Adjust  Injection line leaks  Fix leaks  Restricted fuel return  Clear Rough idle, no  Nozzle trouble  Check, repair or replace abnormal noise or  Fuel-supply pump problem  Check, replace if necessary smoke  Uneven fuel distribution to  Selectively replace nozzles until nozzles condition clears up  Incorrect or dirty fuel  Flush system-use correct fuel Rough idlewith  Injection-pump timing off  Retime abnormal noise and  Nozzle trouble  Check in sequence to find  Complaint Possible Cause Check or Correction smoke defective nozzle  Plugged fuel filter  Replace filter Idle okay but misfires  Injection-pump timing off  Retime as throttle opens  Incorrect or dirty fuel  Flush system-use correct fuel  Incorrect or dirty fuel  Flush system-use correct fuel  Restricted fuel return  Clear  Plugged fuel-tank vent  Clean Loss of power  Restricted fuel supply  Check fuel lines, fuel-supply  Plugged fuel filter pump, injection pump  Plugged nozzles  Replace filter  Air in fuel system  Check for cause and correct  Gasoline in fuel system  Replace fuel Noise – ―rap‖ from  Air in high-pressure line  Bleed system one or more cylinders.  Nozzle sticking open  Replace defective nozzle  Engine problems Combustion noise  Timing off  Reset with excessive black  Injection-pump trouble  Replace pump smoke  Nozzle sticking open  Clean or replace  Internal engine problems 1.3 Engine Tune-up Tools and Equipment Quick and accurate diagnosis and service of the engine require the use of various test instruments and gauges. These will show if the battery, starting, charging, fuel ignition and emissions systems are operating properly. They would also indicate the mechanical condition of the engine.  1.3.2 Compression Tester The cylinder compression tester measures the ability of the cylinders to hold compression while the starting motor cranks the engine. The compression tester is a pressure gauge that measures the amount of pressure or compression, built-up in the cylinder during the compression stroke. How well a cylinder holds compression is an indication of the condition of the piston, piston rings, cylinder wall, valves and head gasket. The dial face on the typical compression gauge indicates pressure in both pounds per square inch (PSI) and metric kilopascals (kPa.). Most compression gauges have a vent valve that holds the highest pressure reading on its Figure 1:1 Compression Tester meter. 1.3.3 Cylinder Leakage Tester The cylinder leakage tester checks compression but in a different way. It applies air pressure to the cylinder with the piston at TDC on the compression stroke. In this position, the engine valves are closed. Very little air should escape from the cylinder if the Figure 1:2 Cylinder Leakage Tester engine is in good condition. 1.3.4 Tachometer The tach counts how many times per second a mark on the pulley passes by. The magnetic tachometer is usually combined with the magnetic timing tester. It uses a probe inserted in the engine probe hole. The probe reacts to a mark on the crankshaft pulley or to a pulse ring or location indicator on the crankshaft. On an engine with electronic engine control system (EEC), engine-speed data is available through the diagnostic connector. A scan tool or a computerized engine analyzer can Figure 1:3 Tachometer display the rpm. 1.3.5 Dwell Meter The dwell meter electrically measures how long the contact points remain closed during each ignition cycle of a contact-point ignition system. The average for all cylinders is then displayed in degrees of distributor-cam rotation. The technician can also use the dwell meter to set contact-point gap and to check for unwanted dwell variation as engine speed increases. Excessive variation indicates mechanical trouble in the distributor. In electronic ignition systems, the ECM controls dwell. It is not adjustable. Figure 1: 4 Portable Tachometer The dwell meter is used to check the duty cycle of the mixture-control solenoid in a feedback carburetor. A dwell-tach meter is a single meter that serves as both a dwell meter and a tachometer. This is possible because both meters have two leads and require the same connections. Pushing a button or turning a knob on the meter switches the reading from rpm to dwell. 1.3.6 Engine Vacuum Gauge Figure 1: 5 Dwell Meter The engine vacuum gauge measures intake- manifold vacuum um. The intake-manifold vacuum changes with the load on engine defects. The way the vacuum varies from normal indicates what could be wrong Figure 1:8 Engine Analyzer inside the engine. Before making the test, check that all vacuum hoses are properly connected and not leaking. Make a backpressure test if a restricted exhaust system is indicated. Figure 1: 6 Engine Vacuum Gauge 1.3.7 Exhaust Gas Analyzer The exhaust gas analyzer measures the amount of various gases in the exhaust. The purpose of making these measurements is to help determine the condition of the engine, ignition system, fuel system and emission controls. On a car with a catalytic converter, tail pipe readings made with a two-gas analyzer are often of little value. 1.3.8 Engine Analyzer An engine analyzer combines several testers, meters and gauges into a single piece of portable shop equipment. When connected to the vehicle, the analyzer provides quick and Figure 1:7 Exhaust Gas Analyzer accurate testing and diagnosis of various engine and vehicle systems. Most shop engine analyzers include an oscilloscope. It displays voltage patterns of the ignition system and electronic fuel injectors. Some computerized analyzers include a second screen. 1.3.9 Dynamometer The chassis dynamometer measures engine power and vehicle speed under various operating conditions. The vehicle is driven onto two rollers so the drive wheels can spin the rollers. The rollers drive a power absorber which is usually under the floor. The vehicle remains stationary, but the engine and other components operate the same as on a road test. Meters on a console report wheel speed and torque or power. The power absorber may be a heavy metal flywheel with an inertia weight, the same as the weight of the vehicle. Or the power absorber may be a brake that places a variable load on the rollers. The technician can connect an oscilloscope and a variety of other testers to check the engine under operating Figure 1: 9 Engine Dynamometer conditions. 1.3.10 Stroboscope Timing Light A timing light is a stroboscope used to dynamically set the ignition timing of an Otto cycle or similar internal combustion engine equipped with a distributor. Modern electronically controlled passenger vehicle engines require use of a scan tool to display ignition timing. The timing light is connected to the ignition circuit and used to illuminate the timing marks on the engine's crankshaft pulley or flywheel, with the engine running. The apparent position of the marks, frozen by the stroboscopic effect, indicates the current timing of the spark in relation to piston position. A reference pointer is attached to the flywheel housing or other fixed point, and an engraved scale gives the offset between the spark time and the top dead center position of the piston in the cylinder. The distributor can be rotated slightly until the reference pointer aligns with the specified point on the timing scale. 1.3.11 Oil Pressure Gauge Checking the engine‘s oil pressure gives information about the condition of the oil pump, the pressure regulator, and the entir e lubrication system. Lower-than-normal oil pressures can be caused by excessive engine bearing clearances. Oil pressure is checked at the sending unit passage with an externally mounted Figure 1:10 Stroboscope Timing Light mechanical oil pressure gauge. Various fittings are usually supplied with the oil pressure gauge to fit different openings in the lubrication system. 1.3.12 Injector Nozzle Tester This practical tool helps test diesel injectors for leakage, spray patterns, opening pressure, and leakage between injector needle and injector body. Suitable for pressure-activated injectors. Figure 1:11 Oil Pressure Gauge  Figure 1: 12 Injector Nozzle Tester 1.3.1 Stethoscope A stethoscope is used to locate the source of engine and other noises. The stethoscope pickup is placed on the suspected component, and the stethoscope recep tacles are placed in the technician‘s ears. Some sounds can be heard easily without using a lis-tening device, but others are impossible to hear unless amplified, which is what a stethoscope does. It can also help you distinguish between normal and abnormal noise. Figure 1: 13 a Mechanic Check Engine Noises 1.3.2 Oscilloscope An oscilloscope or lab scope is a visual voltmeter. A lab scope converts electrical signals to a visual image representing voltage changes over a period of time. This information is displayed in the form of a continuous voltage line called a waveform or trace. A scope displays any change in voltage as it occurs. An upward movement of the trace on an oscillo-scope indicates an increase in voltage, and a downward movement represents a decrease in voltage. 1.3.3 Scan Tool A scan tool is a computer designed to communicate with the vehicle‘s computers. Connected to the Figure 1: 14 PC-Based Lab Scopes electronic control system through Figure 1: 15 Scan Tool diagnostic connectors, a scan tool can access diagnostic trouble codes (DTCs), run tests to check system operations, and monitor the activity of the system. Trouble codes and test results are dis- played on a screen or printed out on the scan tool‘s printer. 1.4 Engine Pre-tuning Requirements There are a general pre-tuning requirements before checking engine tune-up. These are 1.4.1 Electrical Issues Electrical issues can be a complete nightmare, and more so while trying to dyno tune your race car. Some of the more common issues that you should be aware of while completing your race project. A. Wiring and Connectors  No exposed wires on engine harness. This can lead to a short to ground and cause melted wires or fire  Solder or crimp all connections. Never twist wires together the connection can and will fail, especially while tuning!  Chassis grounds should be bare metal and cleaned. Poor ground will cause major electrical problems.  Have the battery ground cable the same gage or larger than power cable. Often times we see a smaller gage battery ground cable cause voltage or charging problems when tuning.  Make sure battery voltage is 13~14 volts when engine is running. We see alternator charging issues often on race vehicles as a result of poor grounding or bad alternator. The battery voltage MUST be between 13.5~14v when engine is running. B. Ignition Issues  Make sure you are using at least one step colder spark plug in your performance race application. Stock heat range spark plugs can lead to pre ignition can cause engine damage very quickly.  If running colder spark plugs, don't start and stop your engine when cold. The spark plug takes longer for self-cleaning to occur. If you don't bring the engine up to operating temperature be prepared to change spark plugs more frequently.   Spark plug gap often times needs to be reduced in a forced induction application over the preset plug gap. Generally in a forced induction application 0.025~0.030" plug gap works very well. 1.4.2 Fuel Issues In a performance race application fuel system delivery and operation is paramount for fueling super high power levels. One small issue in the system can cut you short of your desired horsepower level. Check out the list below to make sure you are ready! A. Fuel Pumps  Do not install an in tank style fuel pump with dirt, rust or debris inside of the gas tank. You will be sure to either ruin the pump or clog the pre filter and have fuel pressure starvation while tuning.  When adding a fuel sump tray to your OEM fuel tank make sure you clean out any metal chips, weld slag or debris after you are done.  When you are running an external fuel pump, you will need to run a pre and post fuel filter. The pre and post filters should be stainless material so you can service and clean them over time. Pre-filter fuel filters should be 40-75 micron rating, post-filter fuel filters should be 100+ micron rating. B. Fuel Pressure  Base fuel pressure should be between 40-50 PSI for most any application.  When possible we recommend using a fuel pressure sensor wired into the engine management system you are using. Some systems do not support this. Many systems offer fail safe protection based on fuel pressure. Having a fuel pressure reading while tuning is invaluable information that can allow us to troubleshoot a fueling problem instantly.  When installing any super high flowing fuel pumps you need to upgrade the OEM fuel pressure regulator. The stock regulators in most cases cannot bypass enough fuel, and the base fuel pressure becomes way too high.  Many newer OEM fuel systems are a return less style system, and lack an external fuel pressure regulator. Because the fuel pressure does not increase at a 1:1 rate under boost, the fuel delivery under boost can be substantially decreased. You may need to upgrade to a return style fuel system in order to achieve much higher power levels.   Make sure the vacuum line going from the intake manifold to the external fuel pressure regulator is secured with zip ties or similar, and is free of cracks or tears.  Make sure you have a 1/2 tank of fuel for the tuning session. If you run low on fuel, fuel pressure will drop which could damage the engine while doing high rpm pulls. 1.4.3 Mechanical Issues A. Engine  All cylinders should have good compression. A general rule of thumb is not having more than 20 PSI of compression variance between cylinders.  If engine compression is 20 PSI or lower in a cylinder (s), pour a small amount of oil into the cylinder. Redo the compression test "wet" and see if the compression increases. If the compression increases you have a piston ring sealing problem or damage. If it does not, your compression issue is related to the valves.  Make sure your engine oil is full, and bring extra oil with you at the time of the tuning appointment. We have limited oil in stock at the shop.  Make sure the coolant level is full in the engine/coolant system. The cooling system MUST be bleed before the tuning appointment. This can take 1-2 hours to bleed in some cases, which will be billed to you at our shop labor rate of 150.00/hr to resolve before tuning can resume.  Check valve lash before tuning. Too tight of valve lash will lose compression, and reduce power. Too loose will make noise. If using aftermarket cams make sure your valve lash is set to the manufacturers suggested specs. Many engines do not have adjustable lash, ignore this step.  Timing chain or timing belt need to be installed correctly, or engine will be out of "time". In these cases we cannot tune the car for you until the problem is resolved. B. Clutch  Make sure your clutch is rated for the torque capacity of the power you plan to make.  Stock clutches on many higher power applications will not "hold" the torque the engine is producing. Please be aware that if the clutch slips during the tuning session you will be charged for the tune, and will need to return at a later date at a retune rate. This has happened numerous times over the years, so please do yourself a favor and ours and upgrade the clutch if you think there may be an issue! 1.5 Typical Tune-up Procedure The steps in a typical tune-up procedure are given below NOTE: All steps do not apply to all vehicles or to all engines. 1. Test and service the battery and starting motor. 2. Inspect the drive belts. 3. If the engine is cold, operate it for at least 20 minutes at 1500 rpm or until the engine reaches normal operating temperature. Note any problems during warm-up. 4. Connect the engine analyzer or oscilloscope and perform an electrical diagnosis. 5. Perform a comparison test. 6. Remove the spark plugs and inspect the firing ends. 7. Inspect the ignition system. 8. Recheck the ignition system with the oscilloscope. 9. Check the manifold heat-control valve 10. Test the fuel pump with a fuel-pump tester. 11. Clean or replace the air-cleaner filter. 12. Check the action of the throttle valves. 13. Inspect all engine vacuum fittings, hoses and connections. 14. Clean the engine oil-filler cap; inspect the conditions of its gasket or seal. 15. Check the cooling system 16. Inspect the PCV system. 17. If the engine has an air-injection pump, replace the pump inlet-air filter, if used. Inspect the system hoses and connections. 18. If the evaporative-control system uses an air filter in the charcoal canister, replace the filter. 19. Inspect the EGR valve. 20. Adjust the engine valves, if necessary. 21. Adjust the engine idle speed. 22. If the engine has a turbocharger, check the waste gate operation. 23. Tighten the intake and exhaust-manifold bolts to the specified torque. 24. Check the maintenance sticker or the lubrication schedule to see if an oil and oil- filter change is due.  25. While the car is on the lift, check the exhaust system for leaks. 26. Road-test the car on the road. Check for drive ability, power and idling. 2.1 Engine-Related Complaints Many drivability problems are not caused by engine mechanical problems. A thorough inspection and testing of the ignition and fuel systems should be performed before testing for mechanical engine problems. Typical engine mechanical-related complaints include the following:  Loss of power  Engine misfiring  Engine noise  Excessive oil consumption  Smoke from the engine or exhaust  Failed Emission Test The driver of the vehicle knows a lot about the vehicle and how it is driven. Before diagnosis is started, always ask the following questions.  When did the problem first occur?  Under what conditions does it occur?  Cold or hot?  Acceleration, cruise, or deceleration?  How far was it driven?  What recent repairs have been performed? After the nature and scope of the problem are determined, the complaint should be verified before further diagnostic tests are performed. 2.2 Visual Checks The first and most important ―test‖ that can be performed is a careful visual inspection. 2.1.1 Oil Level and Condition The first area for visual inspection is oil level and condition. 1. Oil level—oil should be to the proper level 2. Oil condition   Using a match or lighter, try to light the oil on the dipstick; if the oil flames up, gasoline is present in the engine oil.  Drip some of the engine oil from the dipstick onto the hot exhaust manifold. If the oil bubbles or boils, there is coolant (water) in the oil.  Check for grittiness by rubbing the oil between your fingers. 2.1.2 Coolant Level and Condition Most mechanical engine problems are caused by overheating. The proper operation of the cooling system is critical to the life of any engine. Check the coolant level in the radiator only if the radiator is cool. If the radiator is hot and the radiator cap is removed, the drop in pressure above the coolant will cause the coolant to boil immediately and can cause severe burns when the coolant explosively expands upward and outward from the radiator opening. 2.1.3 Fluid Leaks When inspecting the engine, check it for leaks. There are many different fluids under the hood of an automobile so care must be taken to identify the type of fluid that is leaking. Carefully look at the top and sides of the engine, and note any wet residue that may be present. Sometimes road dirt will mix with the leaking fluid and create a heavy coating. Also look under the vehicle for signs of leaks or drips; make sure you have good lighting. Note the areas around the leaks and identify the possible causes. All leaks should be corrected because they can result in more serious problems. Sometimes smell will identify the fluid. Gasoline evaporates when it leaks out and may not leave any residue, but it is easy to identify by its smell. Figure 2:1 Types of Fluid Leaks  2.3 Exhaust Smoke Diagnosis Examining and interpreting the vehicle‘s exhaust can give clues of potential engine problems. Figure2:2 Exhaust Smoke Diagnosis Basically there should be no visible smoke coming out of the tailpipe. There is an exception to this rule, however, on a cold day after the vehicle has been idling for a while, it is normal for white smoke to come out of the tailpipe. This is nothing else but the water that has condensed in the exhaust system becoming steam. However, the steam should stop once the engine reaches normal operating temperature. If it does not, a problem is indicated. The color of the exhaust is used to diagnose engine concerns. 2.4 Engine Noise Diagnosis More often than not, malfunction in the engine will reveal itself first as an unusual noise. This can happen before the problem affects the drivability of the vehicle. Problems such as loose pistons, badly worn rings or ring lands, loose piston pins, worn main bearings and connecting rod bearings, loose vibration damper or flywheel, and worn or loose valve train components all produce telltale sounds. Unless the technician has experience in listening to and interpreting engine noises, it can be very hard to distinguish one from the other. When correctly interpreted, engine noise can be a very valuable diagnostic aid. For one thing, a costly and time-consuming engine teardown might be avoided. Always make a noise analysis before doing any repair work. This way, there is a much greater likelihood that only the necessary repair procedures will be done. Some engine sounds can be easily heard without using a listening device, but others are impossible to hear unless amplified. A stethoscope is very helpful in locating engine noise by amplifying the sound waves. It can also distinguish between normal and abnormal noise. The procedure for using a stethoscope is simple. Use the metal prod to trace the sound until it reaches its maximum intensity. Once the precise location has been discovered, the sound can be better evaluated. A sounding stick, which is nothing more than a long, hollow tube, works on the same principle, though a stethoscope gives much clearer results. The best results, however, are obtained with an electronic listening device. With this tool you can tune into the noise. Doing this allows you to eliminate all other noises that might distract or mislead you. An engine knocking noise is often difficult to diagnose. Several items that can cause a deep engine knock include: Figure2:3 Technician Uses Mechanical Statoscope  Valves clicking. This can happen because of lack of oil to the lifters. This noise is most noticeable at idle when the oil pressure is the lowest.  Torque converter. The attaching bolts or nuts may be loose on the flex plate. This noise is most noticeable at idle or when there is no load on the engine.  Cracked flex plate. The noise of a cracked flex plate is often mistaken for a rod- or main-bearing noise.  Loose or defective drive belts or tensioners. If an accessory drive belt is loose or defective, the flopping noise often sounds similar to a bearing knock.  Piston pin knock. This knocking noise is usually not affected by load on the cylinder. If the clearance is too great, a double knock noise is heard when the engine idles. If all  cylinders are grounded out one at a time and the noise does not change, a defective piston pin could be the cause.  Piston slap. A piston slap is usually caused by an undersized or improperly shaped piston or oversized cylinder bore. A piston slap is most noticeable when the engine is cold and tends to decrease or stop making noise as the piston expands during engine operation.  Timing chain noise. An excessively loose timing chain can cause a severe knocking noise when the chain hits the timing chain cover. This noise can often sound like a rod- bearing knock.  Rod-bearing noise. The noise from a defective rod bearing is usually load sensitive and changes in intensity as the load on the engine increases and decreases. A rod-bearing failure can often be detected by grounding out the spark plugs one cylinder at a time. If the knocking noise decreases or is eliminated when a particular cylinder is grounded (disabled), then the grounded cylinder is the one from which the noise is originating.  Main-bearing knock. A main-bearing knock often cannot be isolated to a particular cylinder. The sound can vary in intensity and may disappear at times depending on engine load. 2.5 Engine Performance Test As the trend toward the integration of ignition, fuel, and emission systems progresses, diagnostic test equipment must also keep up with these changes. New tools and techniques are constantly being developed to diagnose electronic engine control systems. However, not all engine performance problems are related to electronic control systems; therefore, technicians still need to understand basic engine tests. These tests are an important part of modern engine diagnosis. 2.5.1 Cylinder Power Balance Test The cylinder power balance test is used to check if all of the engine‘s cylinders are producing the same amount of power. Ideally, all cylinders will produce the same amount. To check an engine‘s power balance, each cylinder is disabled, one at a time, and the change in engine speed is recorded. If all of the cylinders are producing the same amount of power, engine speed will drop the same amount as each cylinder is disabled. Unequal cylinder power balance can be caused by the following problems:  Defective ignition coil  Defective spark plug wire   Defective or worn spark plug  Broken valve spring  Damaged head gasket  Worn camshaft  Worn piston rings  Defective lifters, pushrods, and  Damaged piston  Leaking intake manifold  Damaged or burned valves  Faulty fuel injector A Figure2: 4 Power Balance Test power balance test is performed quickly and easily using an engine analyzer, because the firing of the spark plugs can be automatically controlled or manually controlled by pushing a button. Some vehicles have a power balance test built into the engine control computer. This test is either part of a routine self-diagnostic mode or must be activated by the technician. Connect the engine analyzer‘s leads according to the manufacturer‘s instructions. Turn the engine on and allow it to reach normal operating temperature. Set the engine speed at 1,000 rpm and connect a vacuum gauge to the intake manifold. As each cylinder is shorted, note and record the rpm drop and the change in vacuum. As each cylinder is shorted, a noticeable drop in engine speed should be noted. Little or no decrease in speed indicates a weak cylinder. If all of the readings are fairly close to each other, the engine is in good condition. If the readings from one or more cylinders differ from the rest, there is a problem. Further testing may be required to identify the exact cause of the problem. 2.5.2 Cranking Vacuum and Speed Tests Cranking vacuum and speed tests are basic mechanical tests of gasoline engine condition. If the engine is in good shape, all air entering the engine is drawn through the carburetor or injection system, past the valves, and compressed in the cylinders. If the engine is worn, air can leak into the cylinders past valve guides, piston rings, valve seats, or bad gasket, figure 8.3. By checking cranking vacuum, you can tell if all cylinders are drawing air through the induction system. If they are not, air leaks will cause a low or uneven vacuum reading and keep you from tuning the engine for best performance. Figure2: 5 Leakage past the Valves, Rings, and Other Points Different engines produce cranking vacuum readings from 3 to 15 inches of mercury. Some carmakers publish cranking vacuum specifications; others do not. The important things to look for are a steady vacuum and cranking speed. If the battery and starting system are in good condition, do the test as follows: 1. Warm the engine to normal temperature. 2. Connect a vacuum gauge to a manifold vacuum source. Do not connect the gauge to ported vacuum. Check a vacuum diagram to ensure correct connection. 3. Connect a tachometer. 4. Close the throttle and disable the ignition. 5. Crank the engine for 10 to 15 seconds and note the vacuum gauge and tachometer readings. 6. Vacuum and cranking speed (approximately 200 RPM) are steady. The engine probably is mechanically sound. 7. Vacuum and cranking speed are uneven. The engine probably has leakage past valves, rings, or the head gasket.  8. Speed is uneven, but vacuum is steady – You may have a bad starter or worn flywheel ring gear. 9. Cranking speed is normal or high and vacuum is low and slightly uneven – The engine probably has low compression or retarded valve timing. Further testing will pinpoint possible problems indicated by this cranking test. You can do a quick check of the PCV system while cranking the engine. Test cranking vacuum as explained above. Then pinch the PCV hose to the manifold closed with a pair of pliers and repeat the test. Vacuum with the PCV hose closed should be higher than with it open. If there is no change in vacuum, test the PCV system for blockage. Figure2:6 Manifold Vacuum Tester Caution: Do not crank a converter-equipped car for more than 15 seconds to avoid drawing fuel into the catalyst. 2.5.3 Manifold Vacuum Tests Measuring intake manifold vacuum is another way to diagnose the condition of an engine. Vacuum is formed by the downward movement of the pistons during their intake stroke. If the cylinder is sealed, a maximum amount will be formed. Manifold vacuum is tested with a vacuum gauge. The gauge‘s hose is connected to a vacuum fitting on the intake manifold. Normally a ―tee‖ fitting and short piece of vacuum hose are used to connect the gauge. Vacuum gauge readings can be interpreted to identify many engine conditions, including the ability of the cylinder to seal, the timing of the opening and closing of the engine‘s valves, and ignition timing. Ideally each cylinder of an engine will produce the same amount of vacuum; therefore, the vacuum gauge reading should be steady and give a reading of at least17 inches of mercury (in. Hg). Figure 1: 16 Vacuum Gauge If one or more cylinders produce more or less vacuum than the others, the needle of the gauge will fluctuate. The intensity of the fluctuation indicates the severity of the problem. For example, if the reading on the vacuum gauge fluctuates between 10 and 17 in. Hg we should look at the rhythm of the needle. If the needle seems to stay at 17 most of the time but drops to 10 and quickly rises, we know that the reading is probably caused by a problem in one cylinder. Fluctuating or low readings can indicate many different problems. For example, a low, steady reading might be caused by retarded ignition timing or incorrect valve timing. A sharp vacuum drop at regular intervals might be caused by a burned intake valve. Other conditions that can be revealed by vacuum readings follow:  Stuck or burned valves  Worn rings or cylinder walls  Improper valve or ignition timing  Leaking head gaskets  Weak valve springs  Vacuum leaks  Faulty PCV, EGR, or other  Restricted exhaust system emission-related system  Ignition defects  Uneven compression 2.5.4 Oil Pressure Testing An oil pressure test is used to determine the wear of an engine‘s parts. The oil pressure test is performed with an oil pressure gauge, which measures the pressure of the oil as it circulates through the engine. Basically, the pressure of the oil depends on the efficiency of the oil pump and the clearances through which the oil flows. Excessive clearances, most often caused by wear between a shaft and its bearings, will cause a decrease in oil pressure. Loss of performance, excessive engine noise, and poor starting can be caused by abnormal oil pressure. When the engine‘s oil pressure is too low, premature wear of its parts will result. Excessive bearing clearances are not the only possible causes for low oil pressure readings; others are:  Oil pump-related problems,  Plugged oil pickup screen,  Weak or broken oil pressure relief valve,  Low oil level,  Contaminated oil, or low oil viscosity. Higher than normal readings can be caused by:   Too much oil,  Cold oil,  High oil viscosity,  Restricted oil passages, and a faulty pressure regulator 2.5.5 Compression Test Internal combustion engines depend on compression of the air-fuel mixture to maximize the power produced by the engine. The upward movement of the piston on the compression stroke compresses the air-fuel mixture within the combustion chamber. The air-fuel mixture gets hotter as it is compressed. The hot mixture is easier to ignite, and when ignited it generates much more power than the same mixture at a lower temperature. Figure2: 7 Compression Test If the combustion chamber leaks, some of the air-fuel mixture will escape when it is compressed, resulting in a loss of power and a waste of fuel. The leaks can be caused by burned valves, a blown head gasket, worn rings, slipped timing belt or chain, worn valve seats, a cracked head, and more. An engine with poor compression (lower compression pressure due to leaks in the cylinder) will not run correctly. If a symptom suggests that the cause of a problem may be poor compression, a compression test is performed. Carmakers publish compression specifications in one of two ways:  Specifications may list a minimum pressure and an allowable variation between cylinders. For example, minimum compression may be 120PSI with a 20-PSI difference between cylinders. Compression, then, would be okay if each cylinder is at least 120 to 140 PSI.  Specifications may say that the lowest cylinder must be within 75 percent of the highest cylinder. If the highest cylinder is 140PSI, the lowest should be 105PSI (75 percent of 140) or higher. In either case, less compression variation among cylinders indicates an engine in better condition. Even if a carmaker does not list a minimum compression, you can suspect a worn engine if compression is below 85 to 100 PSI. A. Wet Compression Test If the compression test reading indicates low compression on one or more cylinders, add three squirts of oil to the cylinder and retest. This is called a wet compression test, when oil is used to help seal around the piston rings. Caution: Do not use more oil than three squirts from a hand-operated oil squirt can. Too much oil can cause a hydrostatic lock, which can damage or break pistons or connecting rods or even crack a cylinder head. Perform the compression test again and observe the results. If the first-puff readings greatly improve and the readings are much higher than without the oil, the cause of the low compression is worn or defective piston rings. If the compression readings increase only slightly (or not at all), then the cause of the low compression is usually defective valves. NOTE: During both the dry and wet compression tests, be sure that the battery and starting system are capable of cranking the engine at normal cranking speed. B. Running (Dynamic) Compression Test A compression test is commonly used to help determine engine condition and is usually performed with the engine cranking. What is the RPM of a cranking engine? An engine idles at about 600 to 900 RPM, and the starter motor obviously cannot crank the engine as fast as the engine idles. Most manufacturers‘ specifications require the engine to crank at 80 to 250 cranking RPM. Therefore, a check of the engine‘s compression at cranking speed determines the condition of an engine that does not run at such low speeds. But what should be the compression of a running engine? Some would think that the compression would be substantially higher, because the valve overlap of the cam is more effective at higher engine speeds, which would tend to increase the compression. A running compression test, also called a dynamic compression test, is done with the engine running rather than during engine cranking as is done in a regular compression test. Actually, the compression pressure of a running engine is much lower than cranking compression pressure. This results from the volumetric efficiency. The engine is revolving faster, and therefore, there is less time for air to enter the combustion chamber. With less air to compress, the compression pressure is lower. Typically, the higher the engine RPM, the lower the running compression. For most engines, the value ranges are as follows:  Compression during cranking: 125 to 160 PSI  Compression at idle: 60 to 90 PSI  Compression at 2,000 RPM: 30 to 60 PSI As with cranking compression, the running compression of all cylinders should be equal. Therefore, a problem is not likely to be detected by single compression values, but by variations in running compression values among the cylinders. Broken valve springs, worn valve guides, bent pushrods, and worn cam lobes are some items that would be indicated by a low running compression test reading on one or more cylinders. C. Performing A Running Compression Test To perform a running compression test,  Remove just one spark plug at a time.  With one spark plug removed from the engine, use a jumper wire to ground the spark plug wire to a good engine ground. This prevents possible ignition coil damage.  Start the engine, push the pressure release on the gauge, and read the compression.  Increase the engine speed to about 2,000 RPM and push the pressure release on the gauge again.  Read the gauge.   Stop the engine, reinstall the spark plug, reattach the spark plug wire, and repeat the test for each of the remaining cylinders.  Just like the cranking compression test, the running compression test can inform a technician of the relative compression of all the cylinders. 2.5.6 Cylinder Leakage Test If a compression test shows that any of the cylinders are leaking, a cylinder leakage test can be performed to measure the percentage of compression lost and to help locate the source of leakage. A cylinder leakage tester applies compressed air to a cylinder through the spark plug hole. The source of the Figure2:8 Leakage Test Process compressed air is normally the shop‘s compressed air system. The tester‘s pressure regulator controls the pressure applied to the cylinder. A gauge registers the percentage of air pressure lost when the compressed air is applied to the cylinder. The scale on the gauge typically reads 0% to 100%. The amount and location of the air that escapes give a good idea of the engine‘s condition and can pinpoint where compression is lost. A zero reading means there is no leakage in the cylinder. Readings of 100% indicate that the cylinder will not hold any pressure. Any reading that is more than 0% indicates there is some leakage. Most engines, even new ones, Figure 2:9 Typical Standard of Leakage experience some leakage around the rings. Up to 20% is considered acceptable. When the engine is running, the rings will seal much better and the actual leakage will be lower. The location of the compression leak can be found by listening and feeling around various parts of the engine. 2.6 Exhaust Gas Analysis The final step in general engine testing is exhaust analysis. For thorough testing, check the exhaust at idle and at 2,500 rpm with the engine warmed to normal operating temperature. Checking the exhaust at idle and at cruising – speed rpm allows you to test the idle and main- metering fuel circuits and emissions at basic and advanced timing. 2.6.1 Exhaust Gases A popular method of engine gas analysis, involves the use of five-gas exhaust analysis equipment. The five gases analyzed and their significance include: A. Hydrocarbons Hydrocarbons (HC) are unburned gasoline and are measured in parts per million (ppm). A correctly operating engine should burn (oxidize) almost all the gasoline; therefore, very little unburned gasoline should be present in the exhaust. Acceptable levels of HC are 50 PPM or less for vehicles with catalytic converter. High levels of HC could be due to excessive oil consumption caused by weak piston rings or worn valve guides. The most common cause of excessive HC emissions is a fault in the ignition system. Items that should be checked include: Spark plugs Spark plug wires Distributor cap and rotor (if the vehicle is so equipped) Ignition timing (if possible) Ignition coil B. Carbon Monoxide Carbon Monoxide (CO) is unstable and will easily combine with any oxygen to form stable carbon dioxide (CO2). The fact that CO combines with oxygen is the reason that CO is a poisonous gas (in the lungs, it combines with oxygen to form CO2 and deprives the brain of oxygen). CO levels of a properly operating engine with catalytic converter should be less than Figure 2: 10 Source of Leakage and Probable Cause 0.5%. High levels of CO can be caused by clogged or restricted crankcase ventilation devices such as the PCV valve, hose(s), and tubes. Other items that might cause excessive CO include: Clogged air filter Incorrect idle speed Too-high fuel-pump pressure Any other items that can cause a rich condition C. Carbon Dioxide (CO2) Carbon dioxide (CO2) is the result of oxygen in the engine combining with the carbon of the gasoline. An acceptable level of CO2 is between 12% and 15%. A high reading indicates an efficiently operating engine. If the CO2 level is low, the mixture may be either too rich or too lean. D. Oxygen (O2) The next gas is oxygen (O2). There is about 21% oxygen in the atmosphere, and most of this oxygen should be ―used up‖ during the combustion process to oxidize all the hydrogen and carbon (hydrocarbons) in the gasoline. Levels of O2 should be very low (about 0.5%). High levels of O2, especially at idle, could be due to an exhaust system leak. E. Oxides of Nitrogen (NOx) An oxide of nitrogen (NO) is a colorless, tasteless, and odorless gas when it leaves the engine, but as soon as it reaches the atmosphere and mixes with more oxygen, nitrogen oxides (NO2) are formed. NO2 is reddish-brown and has an acid and pungent smell. NO and NO2 are grouped together and referred to as NOx, where X represents any number of oxygen atoms. NOx, the symbol used to represent all oxides of nitrogen, is the fifth gas commonly tested using a five-gas analyzer. The exhaust gas recirculation (EGR) system is the major controlling device limiting the formation of NOx. Figure 0-1 Acceptable Exhaust Emissions include  2.6.2 Exhaust Gas Test Procedure Sample the exhaust at idle and at 2,500 rpm as follows: 1.Using the engine inspection procedure from the beginning of this chapter, be sure that: a. The air filter is installed properly and not clogged b. The choke is fully open and is not stuck c. All vacuum line connections are secure and not leaking d. The exhaust system is not leaking and the manifold heat control valve will open correctly 2.Be sure the engine is at normal operating temperature and the analyzer probe is installed properly in the tail pipe. 3.Disconnect the outlet line from the air injection pump or pulse air valve. 4.Check and adjust the ZERO and SPAN setting on the analyzer, if required. 5. Run the engine at normal slow idle and note the HC and CO readings (also CO2 and O2 if using a 4 – gas analyzer). 6.Increase engine to a steady 2,500 rpm and again note all meter readings. Return the engine to idle and note any change in meter readings as the engine decelerates. Note the meter readings again as the engine runs at steadily idle speed. HC and CO emissions should be within legal limits or within the guidelines. Emissions will increase during closed – throttle deceleration, but the readings in step 7 should be as low as, or lower than, the readings in step 5. 2.6.3 O2 and CO2 Analysis CO emissions are directly related to air-fuel mixture. High CO results from a rich mixture, too much gasoline, or not enough air. A. Common Causes of High CO Emissions 1. A restricted air filter 2. Restricted air passages in the carburetor or injection system. 3. A rich carburetor or injection fuel adjustment. 4. High float level in the carburetor 5. A stuck or improperly adjusted choke 6. Leaking power valve or accelerator pump in the carburetor. 7. Wrong idle speed  8. Engine oil contaminated by fuel due to excessive blow by or a leaking fuel pump. You can isolate this problem by disconnecting the PCV valve from the crankcase and letting it draw fresh air while monitoring exhaust CO. If CO drops by 0.5 percent or more, the oil is probably contaminated with fuel. High HC emissions indicate unburned fuel in the exhaust. Incomplete combustion due to a lack of ignition (misfire) or a lean mixture will cause high HC. Although ignition problems often cause high HC, engine mechanical problems and vacuum leaks can also increase HC emissions. B. Common Causes of High HC Emissions 1. Wrong ignition timing 2. Fouled or worn spark plugs, defective secondary cables, worn breaker points, and other ignition problems that cause a misfire. 3. An overly rich or lean air-fuel ratio. 4. Low compression (incomplete combustion) 5. Vacuum leaks at the carburetor, the manifold, the injection system, 6. Worn valve train parts. 7. Worn cylinders and piston rings C. Combined High Readings For HC And CO 1. Defective catalytic converter or PCV system. 2. A defective thermostatic air cleaner or restricted air filter. 3. A defective manifold heat control valve D. Rules of thumb for basic HC and CO testing High HC emissions indicate a lean mixture or misfire – unburned fuel High CO emissions indicate a rich mixture E. O2 And CO2 Gas Analysis Late – model cars with catalytic converters can reduce HC and CO at the tailpipe to levels where they are almost no measurable. CO2 and O2 , however, can be measured. On a non- catalyst car, high HC indicates unburned gasoline in the exhaust. This is usually due to a lean misfire. On a converter – equipped car, O2 indicates a lean condition. If O2 is above 2.0 percent, the air-fuel mixture is probably lean. If O2 is above 4 percent, the mixture is definitely too lean. At the stoichiometric 14.7:1 air-fuel ratio, HC and CO emissions should be low. Similarly, O2 should be low, but CO2 should be high. At lean air fuel ratios, O2 increases and CO2 decreases. Also at a 14.7:1 air-fuel ratio, the total percentage of CO and CO2 is about 14.7 percent. Acceptable combustion in a converter – equipped car will produce the following 4 – gas analyzer readings. HC and CO – within specifications O2 – 1.0 to 2.0 percent CO2 – above 10 percent (ideally 13 to 15 percent) Self-check 2.1 Directions: Answer all the questions listed below. Part I: Say True or False 1. Most mechanical engine problems are caused by overheating. 2. A dwell meter is very helpful in locating engine noise by amplifying the sound waves. 3. High CO results from a rich mixture, too much gasoline, or not enough air. 4. If CO drops by 0.5 percent or more, the oil is probably contaminated with fuel. 5. Always make a noise analysis before doing any repair work Part-II: Choose the appropriate answer from the given alternatives 1. If O2 exceeds CO and CO is above 0.5 percent, the catalytic converter may be defective. If CO is above 0.5 percent and also higher than O2, the converter probably is okay, but the air fuel mixture is rich. a. Technician A b. Technician B c. Both A and B d. Neither A nor B 2. Technician A says that black exhaust smoke is an indication of a too-rich air-fuel mixture. Technician B says that white smoke (steam) is an indication of coolant being burned in the engine. Which technician is correct? a. Technician A b. Technician B c. Both A and B d. Neither A nor B 3. Technician A says that cranking vacuum should be the same as idle vacuum. Technician B says that a sticking valve is indicated by a floating valve gauge needle reading. Which technician is correct? a. Technician A b. Technician B c. Both A and B d. Neither A nor B 4. Two technicians are discussing a cylinder power balance test. Technician A says the more the engine RPM drops, the weaker the cylinder. Technician B says that all cylinder RPM drops should be within 50 RPM of each other. Which technician is correct? a. Technician A b. Technician B c. Both A and B d. Neither A nor B 5. A cylinder leakage (leak-down) test indicates 30% leakage, and air is heard coming out of the air inlet. Technician A says that this is a normal reading for a slightly worn  engine. Technician B says that one or more intake valves are defective. Which technician is correct? a. Technician A b. Technician B c. Both A and B d. Neither A nor B 6. The low oil pressure warning light usually comes on ______________. a) Whenever an oil change is required b) Whenever oil pressure drops dangerously low (3 to 7 psi) c) Whenever the oil filter bypass valve opens d) Whenever the oil filter anti-drain-back valve opens 7. A compression test gave the following results: cylinder #1 = 155, cylinder #2 = 140, cylinder #3 = 110, and cylinder #4 = 105. Technician A says that a defective (burned) valve is the most likely cause. Technician B says that a leaking head gasket could be the cause. Which technician is correct? a. Technician A b. Technician B c. Both A and B d. Neither A nor B 8. An engine noise is being diagnosed. Technician A says that a double knock is likely to be due to a worn rod bearing. Technician B says that a knock only when the engine is cold is usually due to a worn piston pin. Which technician is correct? a. Technician A b. Technician B c. Both A and B d. Neither A nor B Part-III: Give a short answer for the following table No Description Probable Source 1. Honey or Dark Grease 2. Green Sticky Fluid 3. Slippery Clear or yellowish 4. Slippery Red Fluid 5. Bluish Watery Fluid Operation Sheet 2.1 Operation Title: Power Balance Test Instruction:  Keep safe your working area  Refer to your vehicle's service manual to obtain the manufacturer's specifications Purpose: To check an engine performance Required Tools and Equipment: Engine Test Light and electrical plier Precautions: Before making a test make sure engine safe conditions Quality Criteria: - Check properly the engine performance Procedures: Testing Power Balance of Gasoline Engine steps in the process are noted below. Step 1: Visually inspect the engine to determine the best method to disable the cylinders. If this involves connecting a scan tool, installing vacuum lines on each coil, or removing spark plug wires, prepare the engine accordingly. If necessary, disable the idle control system. Step 2: Engine Warm-up. Start the engine and allow it to idle. Record the idle rpm. Step 3: Using the method chosen to disable cylinders, disable the first cylinder and record the rpm. (Do not leave the cylinder disabled for more than a few seconds). Note: For Ignition System – Distributor Type: If the vehicle is equipped with distributor, disconnect one spark plug at a time from the distributor cap (it is good to use a test lead to ground the spark at the distributor cap terminal to prevent the spark from damaging the ignition module in the  distributor), which shuts down the spark for the cylinder being tester. Note: For Fuel System – EFI: To disable the fuel injectors that are accessible, disconnecting the electrical connector from each injectors one at a time will shut off the fuel to the cylinder. Step 4: Reactivate the cylinder and allow the engine to run Fuel Injector for approximately 10 seconds to stabilize. Then leave the engine to idle for another 10 seconds before proceeding to the next cylinder. Step 5: Repeat the steps on each of the cylinders and record your readings. Determine any necessary action. Testing Power Balance of Gasoline Engine steps in the process are noted below. The two possible ways are:- A. Idle speed-drop test 1.5.1.1 Connect a diesel tachometer to the engine according to the equipment maker‘s direction. 1.5.1.2 Run the engine to normal operating temperature. 1.5.1.3 Loosen a fitting at an injection nozzle or pump outlet line to relief pressure with the engine running at idle. a. If the cylinder is delivering its share then the engine rpm will drop. b. If there is no change or less change in engine rpm or engine sound, it means that cylinder does not produce or produces less power. Note The problem may be:- a. Low compression b. Incorrect valve adjustment or timing c. An injector that is leaking, sticking, or otherwise malfunctioning.  B. Glow plug resistance test On some engines, an idle speed drop test will not work because the pump has a pressure relief rotor. When you reduce pressure to one cylinder (loosening the injector fitting), all pump pressure will drop, and the engine will stop. 1.Run the engine to normal operating temperature, then shut if off. 2.Disconnect the alternator so the ohmmeter will not be damaged by voltage through the engine ground of the electrical systems. 3.Disconnect the electrical leads to all glow plugs. 4.Start and run the engine at idle. 5.Set the ohmmeter on its lowest range and connect one lead to a good ground. 6.Touch the other ohmmeter lead to the terminal of each glow plug and not the meter reading. Note Check the specification (eg. 1.8 to 3.4 ohm). High resistance within the range shows high temperature in a cylinder. Low resistance within the range shows low cylinder temperature. Glow plug resistance, cylinder temperature, and injector opening pressure are directly related. If one injector opens at slightly lower pressure, it admits more fuel and causes higher temperature and resistance. Example Each 0.1ohm resistance difference between cylinders indicates about 30PSI (206.7 kPa) differences in injector pressure opening. Low resistance and low temperatures can indicate insufficient injection. Result Engine Power-balance Test Cylinder 1 2 3 4 5 6 Idling rpm Test rpm Diff/rpm Remark Note: For the remark, write G (Good) if the cylinder is contributing power and write F (Failed) if the cylinder does NOT contribute power.  Observation: ___________________________________________________________________ Operation Sheet 2.2 Operation Title: Compression Test Instruction:  Always wear safety eye protection.  Put transmission in ―park‖ (for automatic) or ―neutral‖ (for manual). Set parking brake and block drive wheels.  Make sure the fuel system is disable to prevent the car from accidental starting. Purpose: To check an engine performance Required Tools and Equipment: Compression gauge kit, spark plug socket, basic hand tools, vehicle service manual and a notepad to record results. Precautions: Before making a test make sure engine safe conditions Quality Criteria: - Properly check the Compression test Before Testing  To ensure that compression readings are accurate, perform the following pre-test procedures.  Make sure the vehicle battery is fully charged, and the starter system is in good condition.  Warm up the engine until normal operating temperature is reached.  Make sure to remove all glow plugs before performing the compression test, or for non- glow plug diesel engine remove all the fuel injectors. Procedures: 1. Run the engine to normal operating temperature; then stop the engine. 2. Use compressed air to blow dirt away from the spark plugs or glow plugs. 3. Remove all spark plugs (gaskets and plug tubes, if installed) or glow plugs  and keep them in cylinder number order for reinstallation. 4. Disable the ignition or diesel injection system. 5. On a gasoline engine, block the throttle and choke linkage fully open to allow air to enter the engine. This also keeps fuel from being drawn through the idle and low- speed circuits of the carburetor, which could flood the engine and reduce cylinder lubrication. 6. Connect a remote starter switch to the engine, if desired. 7. Connect the gauge in to the plug opening of cylinder number 1 by: a. Screwing a gauge adapter into the threaded opening or b. Inserting a tapered rubber gauge adapter into the plug opening and holding it firmly during testing, Using the ignition switch or a remote starter switch, crank the engine for four complete compression strokes on that cylinder. Note the gauge reading on the first and fourth strokes. Disconnect the gauge from the first cylinder and repeat step 7 and 8 on all other cylinders. Compare the gauge readings to the carmaker‘s specifications and the following test guidelines. a) Compression increases steadily on all four strokes and is within specifications – the cylinder compression is okay. b) Compression is low on the first stroke and increases on following strokes but does not reach specifications – the piston rings or cylinder is probably worn. c) Compression is low on the first stroke and increases only slightly on following strokes – the valves may be sticking or burned, or rings may be broken. d) Compression in two side – by – side cylinders is low – the head gasket probably is leaking between the cylinders. e) The gauge reading is higher than normal – that cylinder may have excessive carbon deposits in the combustion chamber. If compression is low in any cylinder, you can continue with a wet compression test as follows:- Caution Do not perform a wet compression test on a diesel engine. Oil in the cylinders may cause premature ignition and engine damage. Wet compression testing is not valid on a horizontal engine because oil will not flow evenly around a horizontal piston. 1. Pour a small amount of oil (about 1 tablespoon or 8 squirts from an oil can) into the cylinder through the spark plug opening. 2. Allow about 30 seconds for the oil to flow around the top of the piston. 3. Repeat step 7 and 8 of the basic compression test. 4. Compare the wet test results to the basic test results for that cylinder. If compression increases by 5 percent or 12 to 14PSI, or more, that cylinder probably has worn rings or cylind