Fuel lift pump running on.

[grancito]

We had some discussion some time back about the lift pump continuing to run after the engine was shut down. As I posted, mine only did that if the engine was cold, but agreed that the relay was on it's way out. However the length of run on has been exactly related to engine temp and consistent, so today with the key off I checked the oil pressure sensor plug and found 12 volts on one pin and connecting it to the third pin the pump ran. Who knows if this is a modification or not, but something to check on before replacing the relay.
The first test was to stop the engine then turn the switch to on and watch the oil pressure fall and as it aproached zero the pump would stop.

[LookerOhio]

I replaced lift pump last Fall and it ran fine now it stalls and each time I notice no pressure at filter bleeder when I crack it open. Should it hold pressure there? I assume it should. What is the circuit to tell it to hold pressure there at the filter?

Thanks,

Tom

[Husker 6.5]

I replaced lift pump last Fall and it ran fine now it stalls and each time I notice no pressure at filter bleeder when I crack it open. Should it hold pressure there? I assume it should. What is the circuit to tell it to hold pressure there at the filter?

Thanks,

Tom

Check for a plugged fuel filter.

Husker 6.5

[jobob307]

I found on one of mine where the lift pump wouldn't the problem was a bad oil pressure gauge. Not the sending unit but the gauge had to replace the instr cluster.

[grancito]

LookerOhio, if the engine is not running, there will be no fuel pressure. If the pump does not function with the engine running, check the oil pressure sender. To test, remove the oil pressure sender plug, which is behind the fuel filter, it protrudes from the engine at an angle, and connect the two outer terminals of the plug with a paper clip, turn the key on, if the pump functions then the sender is faulty.