Examine fuel injection valves for:
1. Excessive carbon on tip of nozzle or in orifice.
2. Erosion of the orifice.
3. Screen plugged with dirt.
The condition of a capsule-type nozzle assembly can be tested on the Caterpillar Diesel Fuel Injection Test Bench, and the rate of leakage of the nozzle assembly can be determined.
Checking Fuel Injection Pump Lifter Washer and Pump Plunger
The timing dimension should be checked and adjusted, if necessary, by setting the fuel injection pump timing dimension with the fuel injection pump off the engine. This will assure that the point of the fuel injection is correct. If the timing dimension is too small, injection will begin early, and if too great, injection will be late.
When pump plunger wear becomes excessive, the lifter washer may also be worn so it will not make full contact with the end of a new plunger. To avoid rapid wear on the end of the new plunger, replace the lifters having washers showing visible wear.
WEAR BETWEEN LIFTER WASHER AND PLUNGER
Fig. A illustrates the contact surfaces of a new pump plunger and a new lifter washer. In Fig. B the pump plunger and lifter washer have worn considerably. Fig. C shows how the flat end of a new plunger makes poor contact with a worn lifter washer, resulting in rapid wear to both parts.
A pump can maintain a satisfactory discharge rate and yet be unserviceable because of delayed timing resulting from wear on the lower end of the plunger. When testing a pump which has been in use for a long time, check the plunger length with a micrometer. Discard the pump if the plunger measures less than the minimum length (worn) dimension.
Inspect the upper diameter of the plunger for wear. Performance of pumps worn in this manner can be checked as described in the Instructions for Fuel Injection Test Bench.