I just want to start by saying this has been a very helpful forum- thanks everyone

This is my situation- I have a 1994 F150, 4.9 inline 6, dual tank setup. I've had this truck just under a year and the rear tank has never worked, so I've been using the front tank only. The truck has been hesitating when I give it gas from a dead stop but never had any problems running smoothly throughout the rest of the RPM range. It has been doing this since I've had it in my possession.

Yesterday, it hesitated from a dead stop like it always does, then began behaving in the same way around 20-30mph. It did this for about 5 minutes until it just stopped running. Now, when I turn the key switch to on, the fuel pump runs continuously... Oddly, when I switch it to the rear tank, the rear pump also runs continuously. I changed the fuel pump in the front tank today, and it still just runs continuously, and my truck just coughs and sputters.

I looked at all my fuel lines running from both tanks all the way to the engine and I can't see any fuel coming out of the lines anywhere... I was thinking maybe I had a leak somewhere which would cause the pump to run without ever achieving a "prime"....?

Is there a third fuel pump in this system that I'm not aware of? Has anyone had this problem before? Is there any common areas where fuel could be leaking causing the fuel pump to run continuously..?

Thanks everyone- I'm at the end of my limited knowledge of this truck

 

The common problem is a bad PCM Computer.

 

A bad PCM would cause the pumps to run continuously without the truck running?

 

Yes it would. That is one of the ways they fail. Most of the time when the pumps run all the time it will not start at all as the injectors will not fire either.

 

Is this what you're referring to?

http://www.autozone.com/autozone/cat...&parentId=57-0

 

No, that link goes to an ICM. You need a PCM Computer.

Go here for more information (EEC and PCM are interchangeable).
Ford Fuel Injection EEC Computers

/

 

Thanks a lot for your help. Do you know where I can purchase one of these units? I can't seem to find one online

 

junkyard, napa.

call around to local parts stores.

do a search on this topic for info on replacing and finding computer.

disconnect battery before you attempt to remove computer.

good luck.

 

I would get an OEM one from a junkyard or ebay before I got one from any parts store.

Pull the PCM out of the truck and find the code on it. You'll need a computer with a matching code.

 

yep, that is what i would also.

some here have had luck with napa.

stay out of autozone.

 

Unless you're buying antifreeze, wipers, or armor-all, that's universally good advice.

 

Thanks Everyone.

I'm not sure if this is the cause though-

I had an old Jeep that had a bad PCM, and it would run while I was cranking the truck, but would not run when I dropped the keyswitch into the "run" position. My F150 will run now in the "run" position on the keyswitch, but it runs very poorly to the point that it will stall and shut off in a few seconds and sometimes not fire at all. Would this still be caused by the PCM?

 

once a pcm goes bad it does random stupid things.

this is not a jeep you are working on.

with engine not running and key in the run position and the fuel pump stays on, then in a ford you usually need a new computer.

 

99 times out of 100, when the fuel pumps run continuously it's because of a bad PCM. I don't know what else to tell you. It could be a bad fuel pump relay, but that doesn't explain the truck running badly. A bad PCM is the only thing that explains your symptoms.

 

you have 3 of us telling you the same thing so factor that in.