I have a 1989 F150 fuel pump will not stay on after starting

Asked by Aug 10, 2015 at 09:40 AM

Question type: Maintenance & Repair

I have replaced the HP Pump on the frame and filter as well as the low pressure pump in the tank. When you first turn the key the pumps come on and the truck will start and run but the pumps cut off and the truck dies after about 30 seconds.

5 Answers

78,145

As you didn't state what engine you have, this a general diagnosis. Check too see if you have the low oil pressure cut off switch right by the oil pressure sender, it maybe bad or you don't have enough oil pressure to close the switch. Did you replace the fuel pump relay? Did you check the inertia switch and connectors? The contacts tend to melt inside the connector.

1 out of 1 people think this is helpful.

It is the 4.9 inline 6 cylinder. I replaced the oil pressure sender and while it is running it shows good pressure on the dash. I have not checked the inertia switch I will do that and I have not replaced the relay I figured if fuel pump came on the relay and inertia switch was working but I also wasn't sure if that was so.

78,145

I have seen a few of these have bad relay grounds that will cause your problem.

I checked the inertia switch and replaced the relay and still have the same problem I will check the ground connections next. I un hooked the fuel line as it came out of the filter just to make sure I was correct that the pump was not staying on when I turned the key on the pump kicked on for a few second and then shut back off just like it had been doing

78,145

That is normal, if the ECM doesn't get a steady signal from the IDM it will shut off the fuel pump by turning off the relay.

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