Fuel pump problem 911.

[lifeguard379]

I changed the fule pump, fule pump relay and checked voltage to the to the fule pump, all is good. When I turned the key I don't hear the fule pump prime but when i use a jumper wire to by pass the EEC (Electroinc Engine Control) the fule pimp primes. I'm wondering if anyone knows where the EEC is located?

 

[MrShorty]

I'm wondering if anyone knows where the EEC is located?

Depends on what you are specifically looking for. The components of the EEC-IV system (such as O2 sensors, MAF, EGR, etc.) are scattered over the engine. The main computer (PCM) is behind the kick panel, passenger side, just below the glove box. The PCM itself usually isn't the problem in a case like this.

Do you have a wiring diagram? When you used "a jumper wire to bypass the EEC", what are you referring to: the EEC fuse or the EEC relay? In either case, this implies that the EEC system isn't getting power. The coil side of the fuel pump relay gets its power from the EEC relay and grounds through the PCM, thus giving the PCM control over when the fuel pump runs.

Here's what I'd do. Double check your reading at the tank. Your post implies that you had 12V to the pump, which I don't think is possible based on the fact that it runs when you bypass something in the EEC power circuit. Locate the fuel pump relay, and see which leads have power there. If the red wire (which comes from the EEC relay) doesn't have 12V, then move to the EEC relay and see what you have at that connector. A wiring diagram will help a lot to see how the current flows through these circuits. I've found that even the wiring diagrams in Chiltons/Haynes are adequate for these circuits (you can access a free electronic copy of Chiltons at www.autozone.com).

 

[lifeguard379]

we didn't have 12v we had 6v at pump, but i thought that was cuz the bat was dead.

but thank you for your help. it pointed me to the EEC fuse, it passed with the multi meter (should just pulled them all to look. never trust that agen.) i had to get a new alt to, so i think the old one surged and blew the fuse.

 

[MrShorty]

we didn't have 12v we had 6v at pump, but i thought that was cuz the bat was dead.

I did the same thing once. I don't fully understand it myself (haven't studied the internal wiring in the PCM), but, for future reference, basically that 6V is a "ghost" voltage that is a byproduct of something in the internal wiring of the PCM.

 

[solitary ogre]

i had a similar problem with my '88 2.9L bronco ll where there was 12v at both fuel pumps but not enough to spin them up unless there was a jumper wire off the battery or from the fuel pump relay. i figure it must be a damaged wire in the harness that crosses over the top of the engine. my fix was to leave that wire in place and run a new wire from the relay along the firewall to the pretty pink wire along the frame below the master cylinder. all has been fine for a couple years now.