Applicable Systems
EMCP 4.2
Symptoms
Hard starting, extended cranking time. Fuel rail pressure low at startup.
Possible Causes
- Leaking fuel injector O-rings causing return-side pressure drop.
- Fuel transfer pump worn and failing to deliver rated flow.
- High-pressure fuel pump internal leakage (wear on plungers).
Troubleshooting Steps
- Step 1: Pressurize fuel return line to 345 kPa and check for external leaks.
No visible fuel seepage at injector hold-down bolts. - Step 2: Measure fuel transfer pump output flow at rated RPM.
Flow ≥ 160 L/h at rated engine speed. - Step 3: Read actual vs desired rail pressure via Cat ET during cranking.
Actual pressure reaches desired within 3 seconds of cranking.
How to Reset
Replace leaking injector O-rings or transfer pump; bleed fuel system; clear codes with Cat ET.
Common Replacement Parts
- Fuel Transfer Pump 384-0033: Fuel Transfer Pump 384-0033
- Injector O-Ring Kit 6V-7238: Injector O-Ring Kit 6V-7238
Frequently Asked Questions
- Q: Can air in fuel cause hard starting?
Yes, air entrained in the fuel system prevents proper high-pressure build-up.
- Q: What is normal fuel rail pressure for C15?
Idle: ~103 MPa; full load: ~160–200 MPa depending on calibration.
Source: Caterpillar C15 Engine Service Manual
Category: Heavy Equipment