Diesel Engine Fundamentals

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Questions and Answers

What is a primary reason diesel engines are more expensive to build than gasoline engines?

They require a more rugged design and a precise fuel system. (correct)

They use a simpler fuel system.

They use a spark to ignite the fuel.

They have a lower compression ratio.

What distinguishes diesel engine ignition from gasoline engine ignition?

Diesel engines use the heat from compressed air while gasoline engines use a spark. (correct)

Diesel engines use a throttle to control air intake, while gasoline engines do not.

Diesel engines use a spark plug while gasoline engines use compressed air.

Diesel engines use a carburetor while gasoline engines use fuel injectors.

Which component is responsible for increasing the fuel pressure to approximately 2,000 - 5,000 psi?

Injector pump (correct)

Fuel transfer pump

Injector nozzle

Fuel filter

What is a characteristic unique to diesel engines regarding air intake?

They operate with an excess of air. Signup and view all the answers

What is the primary function of the fuel filters in a diesel fuel system?

To remove foreign particles and water Signup and view all the answers

Which type of injection pump uses a single set of plungers to supply fuel to all injectors?

Distribution type injector pump Signup and view all the answers

What is the typical range of pressures at which fuel is injected in a diesel engine?

2000 to 5000 psi Signup and view all the answers

What is the approximate low-pressure range of the fuel transfer pump?

4 - 10 psi Signup and view all the answers

Which component of a diesel fuel system stores the fuel on the equipment?

Fuel tank Signup and view all the answers

What is the primary function of fuel lines in a diesel fuel system?

To carry fuel from the tank to the cylinder. Signup and view all the answers

Which component in a diesel fuel system atomizes the fuel before it enters the combustion chamber?

Injector nozzles Signup and view all the answers

According to the provided table, which fuel type has the best fuel economy?

Diesel fuel Signup and view all the answers

In a distributor type injection pump, what mechanism is used to move the plungers to create pressure?

Lobes on a cam ring Signup and view all the answers

Which type of fuel is noted as having the least motor oil contamination?

LP-gas Signup and view all the answers

Which type of injection pump is commonly used on engines of 125 horsepower or greater, due to its ability to delivery larger quantities of fuel?

In-line injection pump Signup and view all the answers

What is the role of the metering valve in a distributor injection pump?

To determine the amount of fuel allowed to enter the pump Signup and view all the answers

What component is utilized in in-line pumps to pressurize fuel?

Plungers in barrels Signup and view all the answers

What feature of the plunger within an in-line pump determines the duration that fuel ports are open or closed?

The spiral groove (helix) Signup and view all the answers

What component in an in-line pump causes the plungers to move inside their barrels?

Camshaft Signup and view all the answers

What component directly controls the position of the plungers helix?

The control rack Signup and view all the answers

What action allows more fuel to be delivered to the injector in an in-line pump?

Turning the plungers so the helix covers the fuel discharge port for the full stroke Signup and view all the answers

Which of the following is NOT a standard test performed on a diesel pump test stand?

Timing test Signup and view all the answers

Which type of fuel line is designed to handle the highest pressures?

Heavy-weight lines Signup and view all the answers

What is a characteristic of heavy-weight fuel lines?

Small inside diameter and thick walls Signup and view all the answers

What is the primary function of fuel leak-off lines in a diesel engine?

To return low-pressure fuel from the injectors and pump to the tank. Signup and view all the answers

What is the recommended method for detecting fuel line leaks?

Use a sheet of paper to check for fuel spray. Signup and view all the answers

When replacing a fuel line, what is the MOST important consideration?

Using a line that is the same size, shape, inside diameter, and length as the original. Signup and view all the answers

What is the primary reason for using a series of filters in a diesel fuel system?

To remove impurities and prevent damage to injection components. Signup and view all the answers

Which of the following is typically the first stage of filtration in a diesel fuel system?

Filter screen at the tank or transfer pump Signup and view all the answers

Which of these filtration methods is a mechanical process that uses a screen to trap particles?

Straining. Signup and view all the answers

What materials are commonly used in filters that work using absorption?

Cotton waste, cellulose, felt, or woven yarn. Signup and view all the answers

What method is typically used for removing water from diesel fuel in a filter?

Magnetic separation Signup and view all the answers

What is the primary function of the chemicals used to treat paper filters in fuel systems?

To cause water to form droplets Signup and view all the answers

How do fuel conditioners added to diesel fuel tanks primarily work?

By causing water to form droplets and settle out Signup and view all the answers

In a fuel system with filters arranged in series, what is a key characteristic?

All fuel must pass through the first filter before moving to the next Signup and view all the answers

What is an advantage of using parallel filters in a fuel system?

A larger volume of fuel can be moved Signup and view all the answers

Failure to maintain fuel filters and water traps can lead to which of the following issues?

Decreased engine power, fuel efficiency, and fuel system damage Signup and view all the answers

Which of the following is NOT considered a basic component of an injector nozzle?

Fuel line Signup and view all the answers

What is 'cracking pressure' in the context of injector nozzles?

The pressure required to open the nozzle valve and allow fuel to spray. Signup and view all the answers

What is a defining characteristic of most modern injector nozzles?

They are closed-type nozzles with pressure acting only on one side of the nozzle valve. Signup and view all the answers

What happens to the nozzle valve in an inward-opening nozzle when cracking pressure is reached?

It retracts into the spray tip. Signup and view all the answers

How does an outward-opening nozzle function when cracking pressure is reached?

It opens outward to deliver the fuel. Signup and view all the answers

What is the typical relationship between cracking pressures of inward and outward opening nozzles?

Outward opening nozzles usually have lower cracking pressure. Signup and view all the answers

What is the consequence of using the wrong type of injector nozzle in an engine?

The engine's power and fuel efficiency may be decreased or the engine may not start. Signup and view all the answers

What should always be consulted before servicing or repairing injector nozzles or the injection system?

The operator's or technical manual. Signup and view all the answers

According to the content, what is the main reason diesel engines may have difficulty starting in cold weather?

The low temperature prevents sufficient fuel vaporization from happening. Signup and view all the answers

What is the common active ingredient found in starting fluids used for diesel engines?

Ether Signup and view all the answers

What is the primary function of glow plugs in diesel engines?

To heat the inside of the combustion chamber to aid in combustion. Signup and view all the answers

Study Notes

Diesel Fuel Systems

Diesel fuel is preferred for modern agricultural equipment due to its lower cost, higher power potential, lower volatility, and safer handling.
Diesel engines differ from gasoline/LPG engines in fuel injection pressure, ignition (heat from compressed air instead of sparks), fuel quality, and throttle control (excess air).
Diesel engines can operate on either two-stroke or four-stroke cycles.
Fuel injection pressure ranges from 2000-5000 psi, requiring precise fuel systems.
Fuel economy: Diesel > LPG > Gasoline
Maintenance level: LPG > Diesel > Gasoline
Weight per horsepower ratio: Diesel > LPG > Gasoline
Cold starting qualities: Gasoline > Diesel > LPG
Acceleration rate: Gasoline ≈ LPG > Diesel;

Parts of a Diesel Fuel System

Fuel tank: Stores fuel.
Fuel lines: Carry fuel from the tank to the cylinders.
Fuel transfer pump: Pumps fuel from the tank through filters to the injector pump (low pressure).
Fuel filters: Remove impurities (particulates and water) from fuel before it enters the injector pump.
Injector pump: High-pressure pump, meters and delivers fuel to injectors.
Injector nozzles: Atomize and spray the fuel into the combustion chamber.

Diesel Fuel System Operation

Diesel systems operate at two pressure levels: (1) low pressure (4-10 psi) to transfer fuel from the tank to the injector pump, and (2) high pressure (2000-5000 psi) to deliver fuel to the injectors.
Two basic types of injector pumps: (1) distribution type - one set of plungers that works together to deliver fuel to all injectors, and (2) in-line type - individual plunger for each injector.

Distributor Injection Pumps

Use one pump to deliver fuel to injectors.
Rotary pump design with cylinder bores and plungers moved by lobes on a cam ring.
Rotor rotates inside a hydraulic head to line up discharge passages with injector ports.
Metering valve controls fuel amount delivered.
Some may have automatic speed/load advance systems.

In-Line Injection Pumps

One plunger per cylinder housed in one common housing.
Suitable for larger engines (>125 horsepower).
Plungers within barrels to pressurize the fuel.
Camshaft moves plungers to deliver fuel.
Spiral grooves (helix) on plungers control fuel delivery timing.

Fuel Lines

Heavy-weight lines: High pressure (up to 5,000 psi).
Medium-weight lines: Moderate pressure (5-45 psi).
Light-weight lines: Low pressure (<5 psi).

Fuel Filters

Filtering system important to avoid damaging the injection system.
Typically has three stages: (1) filter screen, (2) primary filter, (3) secondary filter.
Water traps are often included to remove water.

Injector Nozzles

Atomize and spray fuel into combustion chambers.
Components: Body, Nozzle valve, Spray tip, and Pressure spring.
Fuel pressure opens the nozzle valve and sprays fuel.
Nozzle size, number and angle of the holes control spray pattern.
Two types: (1) Inward-opening, (2) Outward-opening

Starting Diesel Engines

Diesel engines utilize compressed air to ignite the fuel.
Starting fluids (ether) or glow plugs may be necessary in cold weather to heat the combustion chamber and facilitate easier starting.
Consult equipment manuals for recommended starting procedures.

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Description

Test your knowledge on the fundamental components and workings of diesel engines. This quiz covers aspects such as ignition, fuel systems, and the differences between diesel and gasoline engines. Dive into the mechanics that make diesel engines unique and efficient.