fuel pump regulator/ relay
Discussion
Didn't I comment on that at the BBWF last year, Combine?
As stated above, it 'should' only run once the airflow meter flap lifts in response to air being drawn through it. The AFM return spring should cause the flap to open the contact that makes the pump relay run. To check if the contact is closed when it shouldn't be, try unplugging the AFM. If the pump stops, it's the switch making it run.
However... Al (Hargo) had the same issue with his 350 fhc last year. We unplugged the AFM and the pump kept running. It turned out that there was a wire link soldered across the tracks inside the red diode 'relay' module that was making the pump run as long as the ignition was on. We cut the link, 'normal' operation was resumed and as far as I know it still works as it should. The strange thing was that the link appeared to have been done from new, as it was actually the lead of one component that had been used to form the bridge. Presumably the fault had always been there!
As stated above, it 'should' only run once the airflow meter flap lifts in response to air being drawn through it. The AFM return spring should cause the flap to open the contact that makes the pump relay run. To check if the contact is closed when it shouldn't be, try unplugging the AFM. If the pump stops, it's the switch making it run.
However... Al (Hargo) had the same issue with his 350 fhc last year. We unplugged the AFM and the pump kept running. It turned out that there was a wire link soldered across the tracks inside the red diode 'relay' module that was making the pump run as long as the ignition was on. We cut the link, 'normal' operation was resumed and as far as I know it still works as it should. The strange thing was that the link appeared to have been done from new, as it was actually the lead of one component that had been used to form the bridge. Presumably the fault had always been there!
It could just be a bit of clart (tech term 
) that is stopping the AFM flap from closing fully and thus not opening the pump kill switch.
Alternatively it could be that someone has been playing with the AFM flap return spring tension and has loosened it to the point that the springy switch contacts themselves have enough resistance to the spring that they don't open.
) that is stopping the AFM flap from closing fully and thus not opening the pump kill switch. Alternatively it could be that someone has been playing with the AFM flap return spring tension and has loosened it to the point that the springy switch contacts themselves have enough resistance to the spring that they don't open.
She's sorted !!!! brilliant. contacts were touching inside black oblong box on AFM BEFORE turning engine over.So bent them apart slightly - not very techy I know - just enough to stop fuel pump coming on too early.No more pumping when only red dash lights on ! Blaine , do you think the nasty backfire will now stop , was AFM to blame ? Put some new spark plus in 2 days ago and that made a dramatic difference to running and seemingly more crackling , popping /noise .
wedg1e said:
However... Al (Hargo) had the same issue with his 350 fhc last year. We unplugged the AFM and the pump kept running. It turned out that there was a wire link soldered across the tracks inside the red diode 'relay' module that was making the pump run as long as the ignition was on. We cut the link, 'normal' operation was resumed and as far as I know it still works as it should. The strange thing was that the link appeared to have been done from new, as it was actually the lead of one component that had been used to form the bridge. Presumably the fault had always been there!
Wow - that's a safety critical issue - shows how much testing Pektron actually did back in the day, eh???
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