servicing diesel fuel-injection systems

8/7/2019 Servicing Diesel Fuel-Injection Systems

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Name : Dewa Gede Adnya Putra

NIM : 0715213050

Class : VIB

Servicing Diesel Fuel-Injection Systems

SHOP FACTS

In a diesel fuel-injection system, the hydraulic lines must with stand very high pressure

and must be noncorrosive. If a hydraulic line requires replacement, install a new lines as

recommended by the engine manufacturer. The hydraulic lines supplied as service part are

preformed and of the proper length. Care should be used in installing them to avoid twisting

or bending them out of shape. If the lines to be replaced is under other lines, you may have to

remove the upper lines.

Whenever lines are disconnected, the lines, nozzles, and pump fittings must be capped.

This will prevent dirt from entering the fuel system. Cleanliness is very importantwhen

working on the fuel system. A dirt particle so tiny as be almost invisible can clog an injection

nozzle.

In a diesel engine, the fuel must be clean and free of contaminants. Figure 24-1 shows the

fuel filters on one engine. A fuel filter work like the filter used in engine lubricating systems.

It contains a cartridge of filtering material (special pleated paper or fiber mat) through which

the fuel must pass. The filter traps any particles and keeps them from entering the fuel

system. The filter should be replaced at specified intervals.

Fig. 24-1 Changing the filter element in a diesel-engine fuel filter



SHOP SKILLS

1. Injection nozzles should not be removed unless there is evidence that they require

servicing or replacement. Usual indications of trouble include :

a. One or more cylinders knocking b. Loss of power

c. Black exhaust smoke

d. Engine overheating

e. Excessive fuel consumption

2. One way to check for a faulty injection nozzle in a multicylinder engine is to run the

engine at fast idle. Then loosen the connector at each nozzle in turn, one at a time. If

loosening a connector causes the engine speed to drop off, the injection nozzle is

probably working okay. If the engine speed remains the same, then the injection nozzle

probably is not working properly. It could be clogged so that no fuel flows through. Or the holes could be partly clogged so that the spray is inadequate or does not have the

required pattern (Fig. 24-2)

Fig. 24-2 Nozzle spray patterns

3. A variety of nozzle are used, but all have a check valve. The check valve opens when

spray pressure is applied so that the fuel can flow through. When the pressure drops, the

check valve closes the shut off the fuel flow rapidly and completely.

4. To remove an injection nozzle, first remove the fuel-return-line clamp and return line.

Then remove the nozzle hold-down clamp and spacer or other connector arrangement.

Remove the nozzle. Cap the nozzle inlet line and the top of the nozzle.

5. Some manufacturers recommend a spray test of the detached nozzle. This requires a

special hydraulic pump which has a pressure gauge. You attach the nozzle to the pump



and then operate the pump. The fuel should spray from the nozzle when the pump

reaches the specified pressure. When the pressure is released, the spray should stop

abruptly without dripping.

6. If the nozzle does not work properly, it can be disassembled and cleaned. Some

manufacturers recommend replacing a defective nozzle. If you disassemble a nozzle,work carefully to avoid damaging the tip or enlarging the holes.

7. Servicing of the fuel injection pump is a specialized job usually done by a shop that

specializes in fuel-injection work. When the fuel-injection pump requires service, the

technician usually will remove it and install a new or rebuilt pump.

JOB 24 : MULTIPLE-CHOICE TEST

1. Black exhaust smoke may indicate

a. Water in the fuel

b. A defective injection nozzle

c. Oil in the fuel

d. Excessive engine speed

2. One purpose of the nozzle check valve is to

a. Shut off fuel flow rapidly and completely

b. Prevent dirt from entering the nozzle

c. Clean the fuel

d. Allow easy removal of the nozzle

3. If the high-pressure spray from a nozzle hits your skin, the fuel may cause

a. A fire

b. An explosion

c. Dirty hands

d. An infection

4. When disassembling a nozzle, be careful to avoid

a. Scratching the housing

b. Damaging the tip or enlarging the holes

c. Cleaning the holesd. Removing the lubricant

5. A defective fuel-injection pump normally is serviced by

a. The technician overheating it

b. The part department overhauling it

c. Replacing it with a new or rebuilt pump

d. Disassembly and cleaning

servicing diesel fuel-injection systems

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