Fuel pump does not shut off

[DryDog]

I had a similar prob a week ago with low cold idle, FP runs long, and dead bat. I replaced the FPR and thought it was solved (still had low idle when eng was cold.)

Today I drove into town and made a couple stops. When I turned the key to On to come home, I heard the pump come on, but after the 2 second pressurization, it continued to run. Once I got home I had to pull the FPR fuse to shut the pump off. When I put the fuse back in the pump stays off. Until I turn the key to On again.

So it seems to me that the FPR is good because it returns to a deenergized state when the power is removed. And that the ignition switch is good because it does not activate the relay when the fuse is installed.

On the 10 mile round trip the X ran great, smoothe accelleration and plenty of power. The pump does seem louder than normal. Haynes says with the engine running, it is difficult to hear the fuel pump. I can hear it just fine. I am at 148K. As far as I know the fuel filter is original. Should I look there? What about pressure regulator? Haynes says that the PCM activates the FPR to supply initial line pressure to the system. How does the system know it is pressurized?
Sorry this is so windy. Just trying to understand.

 

[Billy177]

sounds like a bad ecu

 

[Opera House]

The ECU does activate the fuel pump relay. ECU would turn the relay off shortly after the engine stopped. The relay contacts can stick closed as they get old. This relay is in the box under the fuse distribution box.

 

[Hotweels]

yep either a faulty relay or the terminal's in the code reader port have fused toghether i have seen both.

if you have a code reader it can also check the fuel pump circuit

 

[Fhantazm]

I had a similar problem recently. The fuel pump would shut off fine, but when the truck was jarred (ie door shut hard, hood shut) it would do the 2 second pressurization, as if the key was turned, the turn off normally. I had several other power related problems, and replaced the positive battery terminal. Have not had the problem since!

 

[DryDog]

Is ECU the EEC-IV?

I don't see ECU in my Haynes. What else is it called and where is it located.

When I replaced the FPR last week, I swapped it for one from Ford. It was black. The 3 relays to choose from were green, yellow, and black. I changed the black one. Could I have changed the wrong one?

 

[Billy177]

on a 91 it should be by the pass side kick panel

 

[DryDog]

FPR was the green one

Is it possible to delete this thread?

Turns out last week when I thought I replaced the FPR, it was actually the WOT relay, what ever the WOT is. Today I followed the wiring diagram and got it right. FP problem solved. I also replaced the fuel filter. That seems to have solved the low cold idle.