Hello Everyone,
I've got a 92 (10-91) E-150 4.9 that is stumping me.
Started dieing one day unless I nursed the gas. Check Engine on.
Now fuel pump won't stop and motor runs like it want's to die. Wouldn't start after I got home and a little ether got it chugging,
but again, runs badly. No fuel leaks noticed. Now it starts every time (don't know why it wouldn't that once)
Fuel pressure 50 lbs at key on, around 42 when running.
I've read a lot of posts on this subject here and cannot diagnose it.
Key on; fuel pump doesn't stop.
New pressure regulator (I saw the posts later).
Pump still runs sounding like a sick cat.
Checked fuses and relays, all good.
Switched horn and fuel pump relay (liked that idea thank you)
Replaced filter.
Followed one direction about unplugging PCM, but got no power before or after key was turned.(pump off of course)
Checked battery connections, good, but no power with PCM unplugged.
After looking for ground pin schematic, everything I found on the 92 didn't look like my PCM plug at all and cannot find pictures for the 91.
Cleaned pins and sockets, greased um up and put it all back together. Re-installed battery (PCM was to the left of brake booster, so I had to remove battery) same issues.
Plugged off return line from motor at tank to see if it held pressure or pump would stop, didn't stop ,but sounded better.
Has held 42 lbs for the last couple of hours. Previously lost pressure over night. Will see tomorrow if it held.
Cannot self test with pump running I read.
Never thought it was the fuel pump or PCM, but running out of options.
Any help would be greatly appreciated!

 

Sounds like a bad PCM.

 

I am not certain but here are some fuel system schematics from a 92 e150 4.9 which hopefully will help you.

 

It was the computer.

 

i have a 1990 351 try a computer one from a unk truck should be fine i know 351 and 302 will interchange may throw a code if not both auto or manual tranyys

 

This is my first time posting to one of these things and it took me a while to figure out how to reply to it. Somebody a while back asked about the REC getting wet and would it cause the continuous fuel pump syndrome. That is absolutely almost 100% of the time the cause whether it gets wet or whether it got wet and ruined the EEC, 90's F series leak water down the engine compartment side of the firewall. This completely soaks the plug and wiring harness for the EEC. I've discovered that running a space heater on the driver's side floor for a few hours will warm up and dry out whatever the problem is and the truck will run normally.the problem is I live in Washington and we have rain so I can't drive this thing to work and end up getting stranded in the parking lot there. When I can figure out how to relocate the EEC I will get a new one, it's a $300 part and I don't want to ruin another one from rain. Also, the EEC it's very vehicle specific I've located a place on the internet and they want the VIN number so they can make sure it's programmed correctly for my specific vehicle.

 

I have seen plenty of Youtube videos about the EEC and there is 3 capacitors that go bad..Soldering in the new ones fixes the run on fuel pump on one of the videos and bad running on other videos