Fuel System PDF

CHAPTER Fuel System introduction The fuel system is responsible for supplying fuel to the diesel engine in the correct quantity and at the right time according to engine requirements. To do this, the fu...

CHAPTER Fuel System introduction The fuel system is responsible for supplying fuel to the diesel engine in the correct quantity and at the right time according to engine requirements. To do this, the fuel must be supplied, filtered, pressurized, metered, and injected. The system may be divided into two parts, supply side and the delivery side. The supply side of the fuel system consists of the fuel tank, fuel pump, filters, and piping. W Fuel is drawn from the tank through a suction strainer by T h e Fuel Pump the fuel pump. The strainer has a screen type element that is protected removes-large debris from the fuel. This protects the pump by the suction strainer. against damage from foreign material. The suction strainer should be removed and cleaned or replaced when required at intervals specified in the appropriate Scheduled Maintenance Program - Maintenance Instruction. It is also recommended that the condensate be drained from the fuel tank at the scheduled interval or more frequently during periods of high humidity. Figure 4.1 Fuel Suction Strainer ITS Locomotive Training Series - Student Text 4-1 a  The gear type fuel pump Suction D ischarae may be driven by a DC or AC motor. The pump is designed to ensure adequate fuel supply at all engine speeds. Note that some stationary and marine ' Body installations may use a mechanically driven fuel pump mounted on the end of the scavenging pump. O n some systems, the fuel Rotor passes through a temperature sensitive flow valve (typically called an M O T valve) before Figure 4.2 Fuel Pump Cross Section flowing to the primary fuel filters. -The M O T valve diverts the fuel through the fuel heat exchanger as required to maintain a constant fuel temperature of 100 degrees F. (37.74 Co) From the heat exchanger, the fuel passes through the primary fuel filters before going to the diesel engine. The primary fuel filters typically consist of one or two 1 3 micron filter elements located in canister type housings. On newer systems, these filters are equipped with a bypass valve. Should the filters become plugged, the back-pressure to the fuel pump will increase. When the pressure difference across the bypass valve reaches 30 psi (206.85 kPa), the valve will open diverting fuel around the filters. In most cases the valve is equipped with a gauge to indicate filter condition. c G G c G The'secondary, or engine mounted fuel G filters, are 2 micron elements located on the front left corner of the diesel engine. As with G the primary filter(s), these filters are equipped c with a bypass valve. G The bypass valve is located under a sight glass to provide a visual indication of plugged G filters. Should the filters begin to plug, the back-pressure to the primary filters will G increase. c; When the pressure reaches 60 psi, the G valve will open to divert the fuel flow. In this case however, the fuel is returned directly to G the fuel tank instead of passing around the c filters. Figure 4.4 Engine mounted fuel filters c As filter condition worsens, more and more fuel is directed back to the tank. and b e 1 sight glasses e 1. RETURN FUEL SIGHTGLASS c 2. 3. BYPASS SIGHT GLASS SPIN ON FUEL FILTERS c/ G As the fuel is diverted, engine performance decreases also. If the filters become severely plugged, the engine will die of fuel starvation. To avoid this kind of problem, G primary and secondary fuel filters should be changed at regular intervals. c From the secondary filters, the fuel is delivered to the injectors by the fuel rails c (supply fuel manifolds) located inside the top deck area of the engine. Jumper lines connect each injector to the fuel rail and fuel circulates freely through each injector cj before exiting out another jumper line to the fuel return rail (return fuel manifold). The injectors use what fuel is necessary for engine demands, the rest serves to cool and G lubricate the injectors. G The fuel returning from the injectors passes through a return fuel check valve and G return fuel sight glass before returning to the fuel tank. The return fuel check holds a certain amount of pressure in the engine to ensure proper injector operation. G Depending on engine requirements, this check valve may be set for 5 , 7 , or 10 G psi.(34.4,48.3, or 69 kPa). The return fuel sight glass provides a visual indication of fuel G system condition. If the system is operating properly, the sight glass will be full of clean clear fuel. Air bubbles may indicate filter problems, suction leaks, or faulty injectors. G G c1 Q G c ITS Locomotive Training Series -Student Text 4-3 1 0  3 3 bld 3 3 cc*) 13 L) 3 3 3 13 3 \Cleanout 19 Figure 4.5 Fuel System, Pictorial Diagram 3 3 Delivery c3 The delivery side of the system consists of the fuel injectors, the 3 layshaft mechanism, and the control device or governor. e) The measuring and timing of the fuel must be carried out simultane- ously, or in the proper sequence and in the simplest manner by every fuel- 3 injection system regardless of type. 3 The fuel must first be delivered to the injection 3 mechanism. 3 The pressure of the fie1 delivered by the injection 3 mechanism must be suffcicientto overcome the pressure of compression. 3 4 The rate of fuel injection must be controlled. 19 The fuel must be broken up or atomized into fine 19 parh'cles. 3 The fuel must be properly distibuted in the combustion chamber. 3 j , I4-4 ElectrMotie Model 567,645 & 710 Series Diesel Engines G G Unit lnjector System e The unit injector system, shown in Figures 4.5a and 4.5b, is a development of the G individual pump injection system. Instead of an individual pump connected to an G injection nozzle by a high-pressure fuel line, the pump and nozzle are combined in a single unit injector which performs all the injection functions. Eliminating the high G pressure fuel piping permits extremely high injection pressures - up to 20,000 or even 30,000 psi. (1 37,900 kPa or even 206,850 kPa) G G Each cvlinder head carries a unit injector, which is actuated by a rocker arm from the camshaft. Within the unit are a pump plunger, which raises the fuel pressure, G meters the charge and times the injection, a delivery valve and a nozzle tip to give the desired spray pattern. c G c G G G e G G G G 6 G c1 G G c G G G G Figure 4.5a Fuel lnjector Figure 4.5b Fuel lnjector - Cross Section 0 G G ITS Locomotive Training Series - Student Text 4-5 I ci  LJ 3. " G, 3 3 Injector Operation ,. LS The unit injector, on being depressed by the rocker arm, takes fuel from the supply system and meters, times, pressurizes, and atomizes the fuel into the engine 3 cylinder. Figures 4.6 illustrates the operation of the injector at approximately a half 3 load position. c) 3 3 3 3 3 c3 TOP OF STROKE BYPASS POINT INJECTION STARTS INJECTION ENDS BOTOM OF STROKE 3. BOTH PORTS OPEN FUEL BELOW PLUNGER BOTH PORTS CLOSE LOWER PORT STARTS LOWER PORT FULLY TO ADMIT FUEL ESCAPES THROUGH UPPER WRT. NO FORCING FUEL INTO CYLINDER TO OPEN ALLOWING FUEL BELOW PLUNGER OPEN. NO EFFECTIVE STROKE w EFFECTIVESTROKE TO ESCAPE Lp ONE COMPLETE DOWN STROKE OF PLUNGER AT "HALF LOAD" POSITION u Figure 4.6 Znjector Fuel Control u 3 In figure 4.6, the injector plunger is at the top of its stroke. Note that both the 3 upper and lower ports are open and fuel is allowed to enter the chamber below the plunger. The plunger has a machined recess called a helix. Fuel flows from the 3 upper port into the helix, and though a drilled pwssage in the plunger. 3 As the plunger begins to move down by the rocker arm, the lower port is 3 blocked by the plunger. Fuel is allowed to escape back through the drilled passage, helix, and upper port. 3 Next, the plunger has moved down far enough to close both ports. At this lc) point, as the fuel is trapped below the plunger, fslrther downward motion of the 9 plunger generates higher fuel pressure. This pressure lifts the needle valve and injection begins. 3 As the plunger continues downwards, the lower port starts to open, allowing d fuel to move up through the drilled passage, escaping through the lower port, ending injection. 3 3 The plunger travel continues until the bottDm of its stroke, however, the lower port is fully open and no injection can take place. GI \ 13 Ir) I4 6 ElecMotive Model 567, 645 & 710 Series Diesel Engines I) 710 645 -I.O? 0 NOTE : EXHAUST VALVES OPEN BEFORE & CLOSE AFTER THE OPENINWCLOSING OF THE CYLINDER AIR PORTS TO MAXIMIZE CYLINDER CHARGING -v PRESSURES. - ' -- 'c c G G c G 0' e Maximum Fuel \ T.D.C. E G G c 4 G G G 42 G Exhaust Valves c Exhaust Valves G 0 G G Exhaust Valves cj Ports Open G c Figure 4.7 Timing Diagram (645 Turbo) c G G G e G CJ ci 43 b c c; ITS Locomotive Training Series - Student Text 4-7 a 0  Ls 3 3 Injection Control 3 The quantity of fuel injected is controlled by rotating the plunger with the rack. 3 The amount of fuel injected increases as the rack moves in. As the plunger rotates, the change in the helix in relation to the ports changes the effective length of the stroke. 3 Figure 4.7 illustrates the effective injection stroke with the rack in different positions. r(*9 3 3 3 Effective Stroke 3 Lower 1 Port T 3 3 NO INJECTION NO INJECTION IDLE HALF LOAD FULL LOAD 3 RACK CLEAR OUT RACK ,088"IN 3 ONE COMPLETE DOWN STROKE OF PLUNGER AT "HALF LOAD" POSITION tp Figure 4.8 Plunger Fuel Control 3 44 Position of the rack is set by the Woodward governor in response to engine speed 3 requests. The governor compares actual engine speed with desired speed and adjusts the fuel rate accordingly. 13 GM has made a significant contribution to the reduction of exhaust smoke and 3 gaseous emissions with the introduction of a new LOW SMOKE fuel injector. The key to the LOW SMOKE injector is the new design LOW SAC spray tip. The spray tip 3 features a 53% reduction in the fuel sac below the needle valve seat. Significantly less 3 fuel remains below the needle valve after it has seated, thereby reducing the potential afterdribble of fuel which causes smoke and undesirable emissions 3 13 EMDEC Electronic Injection Control 3 3 EMDEC is an advanced electronically controlled fuel delivery system which can be original equipment on a locomotive, or retrofit to appropriate engine models. Fuel 3 flow through this system will not be radically different from past applications but injection control is based on an electronic system versus the older mechanical system. 3 This section provides an overview of system operation. For further information, consult 3 the EMDEC Electronic Injection Manual. w) 1 4 lu, 4-8 Electro-Motive Model 567,645 & 710 Series Diesel Engines L, G G-* ~ G G G FUEL FLOW AND SYSTEM COMPONENTS c G As on older systems, an electrically driven pump pulls fuel from the tank through a suction strainer. The pump is now driven by an AC electric motor instead G of the DC motor found on older systems. The wiring and piping G connections remain the same. A motor mounted inverter handles the G conversion from 74VDC to AC G required by the motor. The pump has a capacity of 6.5 gallons (24.6 L) per c minute and is identical to the turbo lube pump. c c1 Figure 4.9 Typical AC motor driven pump G From the pump, the fuel is then c/ forced on to a fuel pre-heater (where 6 equipped). The heater is thermostati- cally controlled to maintain fuel tem- c perature at about 100°F (37.74"C). Maintaining a constant fuel tempera- c ture aids in injection control and helps to ensure consistent engine perform- G ance. e C G Figure 4.10 Suction struiner G G From the pre-heater, fuel is passed through a primary fuel filter G assembly equipped with a 30 psi G (206.85kPa) bypass. Two 13 micron elements in parallel compose the G assembly and have been increased in size from older systems, with each G element measuring 30" (76.2cm) c long and 10" (25.4 cm) in diameter. ci These are the same elements as used in lube oil filtration. The filters G are located on the left side of the locomotive above the lube oil filters. Q 0 Figure 4.1 1 Primary filter assembly G c ITS Locomotive Training Series -Student Text 4-9 II 0  d From the primary filter, fuel 13 passes to secondary filters before 3 continuing to the injectors. The secondary filters are 5 micron 3 spin on units located at the front of the engine, however they have been 3 increased in size to handle the 3 additional fuel flow required for this engine. Note also that the sight I*r, glasses have been eliminated on this engine. The secondaries are 3 equipped with a bypass valve that will route the fuel to the tank if the 3 filters become plugged. Bypass 3 pressure has been increased from 60 psi (413.7 kPa) on older systems 3 to 120 psi (827.4 kPa) with the electronic injection. 3 Figure 4.12 Engine mounted fuel equipment 3 The fuel manifolds used are noticeably larger than past applications and 3 jumpers between the manifold and injectors are now made of flexible braided hose rather than the traditional rigid copper tubing. Only a small portion of the fuel that is 3 circulated through the injectors is used for injection, the remainder lubricates and 1*1) cools the injectors. This excess fuel is directed through the return fuel manifold to a check valve. This valve retains 40 psi (275.8 kPa) back pressure in the manifold and 3 injectors to ensure proper injector filling and aid in starting. 3 The control units for the injection system (2 for 16 cylinder, 3 for 20 cylinder), are mounted on a cold plate on the front of the engine. O n its way back to the tank, 3 return fuel cycles through this plate and cools the injection modules. 3 3 03 3 3 3 3 3 3 3 13 A4 L) b 4-10 Electro-MotiveModel 567, 645 & 710 Series Diesel Engines LI L A  0 0 0 I I I I I I I.I I I I I I I I I I. r-- I I I I I I I I I I- I I I I I I I I I I I I I I I I I I I 1  3 Ls 3 3 I$ ELECTRONIC FUEL CONTROL Ls The electronic fuel control system regulates both timing and metering of fuel to 3 optimize emissions and fuel consumption for various engine loads at any set ambient conditions. In other words, an engine required to produce 4300 horsepower with a fuel 3 temperature of 100°F (37.74"C) and air inlet pressure of 21 psi (144.8 kPa) may inject a different amount of fuel at a different timing with respect to Top Dead Center when 3 compared to the same engine producing 5000 horsepower with a fuel temperature of ir) 60°F (15.54"C) and an air inlet pressure of 27 psi (186.165kPa). 3 The presence of electronic fuel control provides variable fuel delivery as well as the first real computer aided engine troubleshooting tool available on a GM locomotive. 3 Because the computers which control operation of the injectors interface with the EM2000 locomotive control system, shop maintenance personnel are able to monitor 3 the following: 3 many injector functions such as metering, timing, response time to ECM Irp commands (Engine Control Modules) 3 fuel temperature fuel pressure before and after primary filtration 3 engine & aftercooler coolant temperatures 3 engine coolant pressures on left & right banks and discharge to radiator 3 lube oil temperature lube oil pressure from turbo 3 cylinder air inlet pressure 3 engine's capability to handle given loads (displayed as LR%MAX) k3 turbocharger inlet air temperature charge air (cylinder inlet ports) temperature 3 3 At first glance, the most significant change to the engine is the lack of Woodward governor, layshaft, load regulator and overspeed mechanism. These functions are now 3 handled electronically by the ECM's (Engine Control Modules). 6ib b J 3 d 3 b# u) lJ) )3..J Figure 4.14 EZecfronic Fuel Injectors 13 4-12 Electro-MotiveModel 567, 645 & 710 Series Diesel Engines iJ 9 3 f3 3  The injection system uses two TRSTARQES 4 / /-fOFNO.1AND magnetic pickups mounted at the NO.SCRANKPIN rear coupling disk to provide basic timing information. The pickups read the position of timing indicator plates mounted on the coupling disk. As the coupling disk rotates, these plates are moved past the pickups to generate an electronic signal to the ECM's. The first pickup, Synchronous Reference Sensor or SRS, generates one signal per revolution of the engine at four IR9/5RS / TARQET -._ _.- degrees before top dead center of the ASSEMBLY CAMSHAFT DRIVE eND number one cylinder. This signal synchronizes the ECMs with respect to engine speed and Crankshaft Figure 4.17 Timing indicator pickups position. The second pickup, Timing Reference Sensor, or TRS reads the metal spokes of the timing plates located on the coupling disc. There are 36 equally spaced spokes, so each pulse from the TRS indicates the crankshaft has moved 10 degrees. Engine speed is determined by the ECMs from the elapsed time between TRS pulses. The exact timing and duration of injection is controlled and adjusted by the ECM's according to load, performance, and ambient conditions. Timing of injection therefore is no longer adjusted manually in maintenance facilities with tools, instead it has become a software item controlled and varied according to ambient conditions by the engine control computer. Figure 4.18 depicts fuel flow in the electronic injector with the plunger at the top of the stroke and the poppet valve open. Note that clean, cool fuel continually circulates through the upper portion of the injector as supplied by the fuel pump. The openposition of the electrically controlled poppet valve allows the fuel to enter the pump chamber and fill it. This flow of fuel ensures a reliable supply of fuel to keep the injector filled and as on the older systems, serves to cool and lubricate the injector. Figure 4.18 Fuel flow during cooling (no injection) 13 4-14 Electro-Motive Model 567,645 & 710 Series Diesel Engines G, c c.............. G c c Figure 4.19 shows fuel flow in the injector with the plunger moving c downwards. This would take place as the piston is approaching top dead center. As the plunger moves downward with the poppet valve open, no pressure is created, c The fuel displaced by the plunger travels through the open poppet valve into the c lower fuel chamber. c At the exact point that injection is to begin (as determined by the ECM), the electrically controlled poppet valve closes and fuel is trapped in the injector below c the plunger. As plunger motion continues, the trapped fuel is pressurized by the plunger and unseats the needle valve at the injector tip to allow injection. The c, longer the electrically controlled poppet valve remains energized during plunger motion, the more fuel is delivered (metering). ci c When injection is to stop, the poppet valve opens and high pressure fuel from the pump chamber is allowed to escape through the valve to the return fuel line. c When the pressure at the injector tip drops below 2OOOpsi (13790 kPa), the needle c valve closes to stop injection. The point at which injection begins and ends (timing) is completely controlled by the ECM energizing and de-energizing the poppet valve. c c Top View of Injector L c a1 C C Fuel Lubricating c and Cooling c Injector Plunger G High Pressure Bleed Pass Return c/ c Poppet / c; Injection Cycle t Fuel Supply Flow G G 710 Cylinder Head Adapter Collar / Fuel Return Flow Trapped Fuel for Injection ci Bleed Return Fuel G c 0 Figure 4.19 Fuel flow during injection '8 c c - TTS Locomotive Training Series Student Text 4-15 a 0  3 rc3 3 3 FUEL SYSTEM TROUBLESHOOTING 1) Before attempting to determine the cause of a fuel system problem, verify that bb there is fuel in the fuel tank. Occasionally, a stuck or broken fuel level gauge will show fuel in the tank when it is empty. Some of the common fuel system problems 13 are covered here along with suggested solutions. 3 Low or No Fuel Pressure 3 3 Ensure that the fuel pump breaker is in the on position and is not tripping out. With the start switch in prime, verify that the pump and motor are 3 both turning. bd Observe the 6Opsi (413.7 kPa) bypass sight glass, if fuel is present check to 3 make sure the relief valve is not stuck open. 3 Remove and clean the suction strainer and change all fuel filters. 3 Visually examine all piping (internal and external) for leakage, restriction, iu) and partially closed valves. 4 Internal Fuel Leaks 3 W Fuel leaking inside of the engine can be detected by observing a high or rising engine lube oil level, or by lube oil analysis. Large enough quantities of fuel will 3 dilute the lube oil and reduce its lubricating ability. Inspect the top deck area for leakage from injectors, top deck fuel manifolds, and injector jumper lines, paying rclrs particular attention to jumper line seats on the injectors and the fuel manifold. Do not stop looking after one leak is found, but continue until all cylinders have been 3 checked. 3 If no leaks are found, it is possible that the injectors are leaking internally. eJ) Worn out or physically damaged injectors can leak fuel into the cylinders, past the rings, and into the lube oil. 3 3 To check for leaking injectors, perform a ''one revolution" inspection of the engine, checking for fuel, or fuel "washed" appearance in each piston crown. Any Q injectors showing signs of leakage should be replaced with a new or qualified unit. 3 Bubbles in Return Fuel Sight Glass 3 3 The return fuel sight glass (the glass closest to the engine block) should normally be full of fuel and clear of bubbles when the engine is running. If bubbles 64 are observed in the return sight glass, shut the engine down, hold the engine start switch in the fuel prime position, and observe the sight glass. If the bubbles stop, the '.tr) probable cause of the bubbles was an injector with tip leakage, which can be located 4 using the above procedure. L) 4-16 Electrc-Motive Model 567,645 & 710 Series Diesel Engines 3 G G c 6 Fuel in Bypass Sight Glass G Normally the bypass sight glass (the glass farther from the engine block) is empty. c Fuel in this sight glass indicates that the bypass relief valve is open as a result of the back pressure caused by clogged engine mounted fuel filters. If fuel is still present after C changing the fuel filters, the relief valve should be inspected for a broken spring or stuck G plunger. e Intermittent Fuel Starvation G Gi Foreign material in the fuel tank that is too large to go through the fuel suction line can block the intake and cause fuel starvation. When the engine is shut down, or c expires from lack of fuel, the material may be released when the suction from the fuel pump stops. G When the engine is started again, it will run properly, until the material is picked G up again by the fuel pump suction. The fuel tank should be drained to remove the G objects, and if the problem continues, the tank will have to be opened up to clean it out. c Locating a Misfiring Injector G e Individual injectors can be checked for proper operation while installed in the engine by two methods, the injector pressure test and the "clunk" test. c "Clunk" test With the engine at idle speed, remove the spring clip and clevis c pin from each injector control lever one cylinder at a time. Slowly open the rack by pulling outward on the G injector control lever, and then Cj return it to idle position. If the injector is operating properly, the 6 cylinder will fire with a pronounced ''clunk" with the rack advanced. c c Injector Pressure Test (Pop Test): Special tool #4002 1839 is required G to perform this test. c - With the engine shut down, ensure c that the engine fuel lines are fully charged, bar the engine over until 7 5 1 c, the injector cam roller for the g cylinder being tested is below the c exhaust cam rollers (check with straight edge). c I G Figure 4.20 Injector Pop Test Tool ci G c ITS Locomotive Training Series - Student Text 4-17 a 0  - Apply the test tool to the injector rocker arm with the lower end of the times undei the rocker arm shaft and the top of the tool covering the rocker arm adjusting screw lock nut. - Remove the spring clip and clevis pin from the injector control lever and place the injector rack in the full fuel position. - Insert a 1/2 inch drive torque wrench in the test tool, and apply and hold 80ft-bs (107Nm) of torque for a minimum of five seconds. If the torque remains constant without moving the wrench, the injector is acceptable. If the wrench must be moved to maintain the torque or the indication drops off, the injector is leaking and must be replaced. 4-18 Electro-fvlotive Model 567, 645 & 710 Series Diesel Engines c c ,..-.. G e, c SYSTEM MAINTENANCE (EMDEC) ~. li. G Maintenance of the fuel system normally consists of a few minor tasks performed c as part of a scheduled maintenance program. These tasks do not differ significantly from c those performed on a conventional mechanical fuel injection system. G Always consult your company's maintenance instructions for specific inspection items and frequency. G G SCHEDULED MAINTENANCE G Daily or Trip c, The fuel level should be checked frequently to ensure that the engine has an G adequate supply for operation. Running the engine frequently with a low fuel level can lead to early filter failure due to the buildup of condensation and other contaminants in c the tank. It can also can lead to early injector failure since the injectors rely on the fuel c for cooling. A low fuel level will allow temperatures to rise dramatically. Visually check the gauge on the tank to ensure that the fuel level is adequate before dispatching c the unit. Also check the primary fuel filter bypass gauge to ensure the filters are in the serviceable zone. Closely examine all piping and components for damage or leakage, c 90 Day Inspection c c At 90 days, the primary fuel filters should be renewed. With the engine shut down, open the fuel filter access doors. Remove the filter elements, thoroughly clean the tanks, G and renew the 2 paper elements. Apply new seals and secure the access doors. G The secondary (engine mount or twin spin) filters are also renewed on the 90 day c inspection. Pre-fill both elements with clean fuel before applying to the engine, This procedure has not been altered from previous design engines. G 180 Day Inspection c c On 180 day inspection, remove and inspect the suction strainer for debris and contaminants. Clean or replace the element, renewing the canister seal. G 3 Year Inspection G On the 3 year inspection, remove all fuel injectors and replace with qualified G replacements. G 6 Year Inspection c The 6 year inspection is the major inspection interval. Remove and recondition c fuel pump and motor. Renew the drive spider between the motor and pump. Check pump operation before dispatching locomotive. G '0 e G - Ifs Locomotive Training Series Student Text 4-19 a cj  3 Remove all EMDEC control equipment and replace with qualified components. Closely inspect all wiring harnesses, connectors and sensors for defects. Examine the engine timing and speed pickups. Reset air gap on all pickups. Qualify the primary fuel filter bypass valve and gauge, replace if required. Fuel System Troubleshooting (EMDEC) Although troubleshooting procedures on the EMDEC equipped engines are very different to those used on mechanical injection models, as a rule, less problems can be expected with the new system. Troubleshooting the system is easier with the diagnostic capabilities built into the EMDEC system and the EM2000. Conditions in the fuel system can be monitored by the use of a laptop computer connected to EMDEC through an RS-232 communications port in the cab of the locomotive. Fuel temperature and pressure, injector response and engine timing are a few of the items that can now be monitored while the engine is running. Problems with the fuel system generally can be classed as: (1) a loss of fuel pressure to the injectors (supply problem); (2) defective injectors; or ( 3 ) control problems (EMDEC electronics). Low Fuel Pressure (EMDEC) Fuel pressure and temperature is constantly monitored by the EMDEC control unit through the use of a pressure sensor and a temperature probe both located at the fuel distribution block on the front of the engine. This information is used by EMDEC for fuel delivery calculations. Should either condition move outside of normal operating ranges, EMDEC will cause an engine shutdown and display a fault condition. When an engine is reported as having low fuel pressure, the following steps should be taken: 0 check the level of fuel in the tank. 0 check condition of the filters by means of the bypass gauge located by the primary fuel filters. 0 change all fuel filters and clean or replace the suction strainer. 0 visually examine all piping and hoses for leakage or restrictions. 0 determine whether the problem is actually low pressure, or an incorrect reading by the pressure transducer. Fit a mechanical gauge to the pressure sensor location using a "Tee" fitting. When the engine is operating, the gauge and the reading indicated by the sensor should be within a few pounds of each other. If not, replace the sensor with a qualified unit. If the mechanical gauge indicates a true low pressure situation, the procedures for qualifying the system remain the same as in the past. 4-20 Electrdvlotive Model 567, 645 & 710 Series Diesel Engines c c-.... -..... c... e;. G disconnect the fuel return line at the distribution block and attach a length of e; clear hose that will allow fuel return to be observed. Check the return fuel for air bubbles that could indicate a suction leak. Also observe the quantity of fuel c;; flowing with the engine shut down and the pump running. The flow should be between 4 and 5 gallons (15.14 and 19 L.) per minute in order to run the engine at c full power. c Refer to the Engine Troubleshooting Section of the manual, or the separate Diesel G Engine Troubleshooting Guide for further checks. ci G Faulty Injectors (EMDEC) Normally the injectors are controlled by EMDEC and deliver very precise amounts cc/ of fuel. If the injector is faulty, there will be a noticeable change in engine performance. c Injectors can fail in several different manners, but all will impact cylinder power levels. Some of the more common failure modes are: c failure of the energizing coil (open or shorted) will cause a complete failure of c 0 injection as the poppet valve will not seat to build pressure for injection. G 0 a faulty poppet valve (stuck or leaking) will not allow the pressure to build for c injection, or if stuck closed, will not allow the injector to fill below the plunger. c 0 a leaking or badly worn plungerharrel assembly will lead to low injection e pressures and poor performance. G 0 if the injector tip, spring, needle, or check are damaged, the injector Performance will be severely affected. Problems in this area are identical to the e problems found on the older mechanical injectors. c Injector problems can be isolated and identified by two methods. Using the laptop G computer, all injector response data can be monitored and a cylinder cutout test can be performed. Cut out the injectors one at a time with the computer and note engine G response. If a good injector is cut out, there will be a slight change in engine sounds and the fuel delivery rate will be adjusted on all other injectors to compensate. If a faulty G injector is cut out, there will be no change to engine sounds, speed, or injector delivery e rates. This test is similar to performing the ttclunktttest on older systems. G Injection Control Problems (EMDEC) c 4 When troubleshooting a control problem it must be determined: (1) if there is a c true fault; (2) is the pKQb)erF;Irelated to a software problem; or (3) is the problem due to a failure of an EMDEC component or associated wiring or other hardware. It helps to e follow a set routine and logical order of checks when trying to isolate a problem. Verify all simple conditions first and use the control computer and laptop to help diagnose the c problem. G 0 check the fault archive in the EMDEC control unit to verify the system failure. The computer may provide an indication of the cause of the failure such as the G communication between control units, communication fiom the control unit to the injectors, or the failure of a control unit itself. C c ITS Locomotive Training Series -Student Text 4-21 a L9  3 0 check the level of fuel in the tank. 0 check condition of the filters by means of the bypass gauge located by the primary fuel filters. 0 change all fuel filters and clean or replace the suction strainer. 0 visually examine all piping and hoses for leakage or restrictions. 0 determine whether the problem is actually low pressure, or an incorrect reading by the pressure transducer. Fit a mechanical gauge to the pressure sensor location using a "Tee" fitting. When the engine is operating, the gauge and the reading indicated by the sensor should be within a few pounds of each other. If not, replace the sensor with a qualified unit. If the mechanical gauge indicates a true low pressure situation, the procedures for qualifying the system remain the same as in the past. Engine Stafiing Procedure Before attempting to start an engine that is new, remanufactured, or has been shut down for more than 48 hours, engine prelube is to be petformed. This procedure is described in Chapter 6 of this text. Check levels of engine oil, governor oil, compressor oil, and engine coolant. Open cylinder test valves and bar engine over at least one revolution. While closing test valves, watch for discharge of fuel, engine oil, or engine coolant. If any of these are found, determine the cause and make the required repairs. Remove the starting fuse. Check that all fuses are present and in good condition, and of the proper rating. Verdy that the main battery switch is closed, and that the ground relay switch is clssed. Place the local control and the control circuit breakers in the ON position. Place the control and fuel pump switch in the ON position. Place generator field and engine run switches in the OFF position. Turn isolation switch to the START position. B 4-22 Electro-Motive Model 567,645 & 710 Series Diesel Engines.. i '. ,...... I..^.. At the equipment rack in the engineroom, place the Fuel PrimeEngine Start switch in the PRIME position until fuel flows in the return fuel sight glass clear and free of bubbles. Check that the starting fuse is in good condition and proper rating then install it. r -P CAUTION: 6 Do not crank the engine for more than 20 seconds or "inch" the engine with l 9 the starter. After cranking allow a minimum of two minutes for starter cooling before attemptinu another start. If engine is equipped with purge control system, do not push injector rack control lever (layshaft) until engine has cranked for six seconds. Position layshaft at about one third rack (1.6 on the scale), then turn the Fuel PrimeEngine Start switch to the START position. Hold the switch in the START position until the engine fires and speed increases. Release the layshaft when the engine comes up to idle speed. Check that the low water detector is not tripped. If the detector is tripped, wait for one half minute after engine start, then press the reset button and hold for five seconds to reset. If the detector trips again, verify engine oil pressure, then slowly push the layshaft in to increase engine speed momentarily before resetting the button. Check that the cooling water level, lube oil pressure, and governor oil level are all satisfactory. Fuel Storage Facilities Before being added to the fuel tank, it is recommended that diesel fuel be processed through an effective fuel filtration facility that removes soft and hard contaminants 2 microns in size and larger. Using unfiltered fuel can result in suction strainer plugging, loss of performance, and over time, serious damage to injectors. Soft contaminants include water, bacteria, algae, fungi, and waxes. Water must be removed or kept at the lowest possible level, as it is very destructive to fuel system components. Bacteria, algae, and fungi contamination of the fuel storage tank will show *pc *" $1 up as slime on the facilities fuel filtercand may requirt! treahnent with algicide or fungicide to remove it. Waxes are generally kept in suspension and do not cause problems unless there is an excessively high level of them in the fuel or extremely cold temperatures. Hard contaminants such as rust, scale, cracking catalyst fines, dirt, and wear metals will be removed by the filters as long as they are changed at regular intervals, (usually monthly). - ITS LocomotiveTraining Series Student Text 4-23 a c G. ,.>, G c c; c c G G G G c c G c, c c G -- I I G I I I c I 1 I I e, I I G I I :4 G I I I I G I I I G G G CJ c, CJ c; G G G ci