Engine/Transmission (1998.5 - 2002) More Engine Problems

[JMLambert]

After replacing the lift pump and injector pump the truck ran welll. When I started it about 30 minutes later I had to crank on the starter for 3 to 5 seconds which is not normal. The engine usually fires immediately. I drove the truck home parked it shut it off and tried to start it again. It took about 10 to 15 seconds for the engine to fire. When it did there was no fuel pressure. I shut it off and bmped the starter, the lift pump did not engage. The next morning I tried it again and it started immediately with good fuel pressure. It seems as if after the engine runs a problem developes in the electrical system that shut off the lift pump. If allowed to set for a period of time the problem disappears until it is run again then it comes back.

 

[BDaugherty]

Install a relay to power your lift pump if you don't already have one. then just use switched ignition power to trigger it instead of the ecm signal. if it starts and runs correctly, you have found your problem. Then you can decide whether to leave it or fix it.

 

[JLandry]

JM,



Assuming there's nothing wrong with the wiring harness, then the ECM may have an internal problem. The ECM powers the lift pump directly with no fuse or relay in between. Seems like a terrible idea to do it this way, but in fairness it's held up pretty well for the majority of folks.



The next time this happens, it couldn't hurt to verify if power is (or isn't) present at the lift pump wiring harness connector. Just hook up a multimeter to the connector and bump the starter as you usually do. If power IS present and the lift pump still won't run, then obviously the lift pump has a problem. If no power is present, then you can troubleshoot further by separately back-probing pins 15 and 35 of the ECM 50 pin connector for the presence of 12v power (ground your mutilmeter to the neg battery terminal). Both these pins should have an 18 ga yellow wire with a white stripe coming from them. If these pins do have 12v power, then there must be an intermittent break somewhere in the wiring harness between the ECM and lift pump connector. If they don't have power, then either the ECM connector is bad or (more likely) the ECM could have an internal heat-related failure.



John L.