Unit Injector Cranking Rack Position
This procedure checks for worn injectors by evaluating the rack position during cranking.
- Verify that the engine is difficult to start when the engine is hot. If the engine starts easily, run the engine until normal operating temperature is reached or until the hard starting problem occurs.
- Remove the valve cover. Install a dial indicator and 1U-6679 Indicator Group on the No. 1 cylinder.
- Crank the engine and watch dial indicator in order to determine the rack position during cranking. If the rack position during cranking is less than 5 mm (0.2 inch), check for the following problems:
- Binding in the governor
- Binding in the control linkage
- Sticky fuel injection rack
- Misadjusted FRC
Refer to Troubleshooting, "Fuel Injection Control Linkage".
- Binding in the governor
- Crank the engine and push the rack control (1) toward the governor so that a rack position of approximately 10 mm (0.39 inch) is indicated. If the engine does not start, investigate other engine systems before suspecting worn unit injectors as the cause of the problem. Replace all the unit injectors if the engine is easier to start with an increased rack position. Ream the injector sleeves if the seat area for the injector is pitted. Replace the injector sleeves, if necessary. Refer to Tool Operating Manual, NEHS0738, "Using the Injector Seating Tool " and Tool Operating Manual, NEHS0610, "Using the 128-8822 Tool Group on 3114, 3116, and 3126 Engines with Mechanical Unit Injectors (MUI)". Also, refer to Video Tape, LEVN4032, "Troubleshooting Guide for the 3100 Family of Diesel Engines" and Video Tape, LEVN4732, "Injector Seating Procedure". Caterpillar High Efficiency fuel filters are recommended in order to prolong the life of the unit injectors.
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| Illustration 1 | g00609103 |
(1) Rack control (2) No. 1 injector | |
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