Hello all,

I hope everyone here had a great Memorial Day!
Been a while since I've been on here, but my truck is needinig a helping hand and so am I! My truck started running rough, it gives a CEL and has very little power. I tried to pull the codes and the test wouldnt initiate. That's when I noticed that the fuel pump wouldnt turn off with key in run and the engine off. I researched on this site and in my manuals, and went to work. From what Iv'e read, many guys have had this be a bad EEC, but also possibly a bad fuel pump relay. This is what I've done so far:
- Pulled EEC Power Relay and Fuel Pump Relay and ohmed them out. Both read open.
- Ran 12 VDC across each relay's coil. Both relays clicked open and closed.
- Reinstalled both relays, unplugged EEC and turned key to run position. The pump did not turn on. Tried wiggling wires, pump still didnt turn on, so I dont think I have a short anywhere.
- Plugged EEC back in, removed Fuel Pump Relay, left EEC Power Relay in. Turned key to run. I shot the FPR plug for power (the pin that receives power from the EEC Power Relay) and it is receiving 12 volts. The EEC still would not remove the power though.

I'm wanting to double check my work here, but I also dont know what else to check to rule out the EEC. I know if I'm missing something, the answer can be had here. Before I start pricing EEC's, if yall could clue me in on what else I could check, I'd sure appreciate it.

Chris

 

Not being able to pull codes and fuel pumps not shutting off are the two classic signs of a bad PCM.

 

My truck is doing the exact same thing I did replace the eec and it ran fine for about 30 seconds when I first started it then right back to doing the same

 

HD,
The EEC (PCM) power relay is operated by the Ignition Switch and not the computer.
The Power Relay gives power to both the fuel pump relay coil and the Computer.
Sounds like you have check all that needs checking.
And as Andy said above it sounds like a bad computer.

CPFR1924,
If worked OK for 30 seconds and then it started doing it again I would say your replacement computer is now bad also. Take it back to where you got it and get another one. They should not charge anything as you are not the first one to have got a bad computer.
I take it your Alternator is not over charging is it?
Or you did not take a battery cable off with it running did you?
Either one can take out the computer.

 

Thanks for the quick responses guys. It seems it is as I feared. Guess I cant complain, I would think 20 years is a pretty good haul. Time to see how much a new one will run me.

CPFR1924,
I hope another replacement works for you and its not something else frying it or anything. Good luck with that. I plan on posting my results right back here.

Thanks again!
Chris

 

Either your computer was bad from the start or something is wrong with the electrical system in your truck and it's causing the computer to fail.

As Bill said, it's probably a bad ground. Another other electrical problems going on?

 

The alt. Is not over charging and I did have the batt. Cable off for the install, I suppose I will try another computer then and if that don't help maybe a match will lol

 

Hello again,
I pulled the PCM and took a look inside. I read from some research on here that the capacitors are "electroytic" and when they get old the electrolyte leaks out causing corrosion and whatnot. I think that may be my problem. I'm no computer tech, but the contacts on these things look nasty. Here's some pictures. Hopefully a more trained eye can discern it better. Apologies if the pics arent the best. You really gotta work the zoom to photograph these things! Thanks! Please tell me what yall think.

Chris

 

Hello all,

I picked up a new PCM today and installed it. So far its running much better! Fuel pump shuts off like it should, idles right and check engine light is gone. Im about to go take it for a drive. I took pictures of the new computer also and Ill post em up later. Thank you again for all the help!

Chris

 

Just got my new computer and there is no change it didn't ever run right for 30 seconds this time

 

fuel pump?

 

CPFR1924,
Did the pumps not run with the computer unplugged and the key on?

If they did not run the only thing that would do this is a bad computer or power and ground problems.
Did you check the PCM plug to see if you had power on the 3 pins (1, 37 & 57) and ground on the two ground pins (40 & 60) for an OBD1 computer?
If you do not have power and grounds then this could be it.

 

I hav 89 ford f150 5.8 same problem with fuel pump staying on in key on position. i tested the eec ground pin 40 and 60 is giving off 8.5 volts plz help

 

Check the small black wire with a green stripe at the NEG post of the battery and replace it if it is not there.

What is happening is the clock is not running in the computer or the fuel pump relay bad.