Hey, I need some help guys. As some of you may recall, my 1986 F150 was owned by someone who did some, well, interesting work arounds, and then it sat for 3 yrs in a field. Anyway, one of his work arounds was at the FP relay. The fuse link fried because the battery hot got hot next to the engine and shorted out. He never found it and cut out the fuse link. Then he removed the EEC completely from the circuit and jumpered the ignition hot (red) to the fuel pump (brown) with a clip splicer and removed the FP relay. I discovered it when one day I was working on something else and saw the clip smoking. I replaced the entire connector and began trying to figure out how to get the fuel pump circuit working correctly again. I put in a new 30 amp fuse on the yellow at the solenoid, rewired a new EEC relay connector in and put in the relay. Everything there checks out okay. But if I put in a FP relay I get nothing, and I've tracked it down to the tan/light green wire to pin 22 on the EEC module. I read in another post that it is that wire that grounds the fuel pump circuit, but it isn't working. There is no continuity at the relay harness (I jumped it with a test light from red to tan/light green and got nothing). I dread the thought of running every inch of that tan/light green wire, but apart from that it has to be at the EEC, which is also an unhappy thought. And yes, the impact switch is fine. I've checked it (unless there are two in the circuit). The one I found is above and right of the tranny hump with a white button on it. It has a constant hot (yellow) in and out, and when the ignition is "On" I get current on both sides. The fuel pumps work normally if you jumper red to brown at the relay connector.

 

If the EEC does not see a signal from the distributor module, it thinks the engine is not turning and will not ground that wire to activate the fuel pump relay.

 

Hmm. But the fuel pump must run before the engine is cranked in order to have fuel pressure to start. Right? Also, by distributor module do you mean the TFI? If so, it's working fine. I guess I'm not understanding all that is involved here. Thanks.

 

The EEC will turn the pump on initially when the key is first turned to run. But after that, it looks for the signals from the TFI module to verify the engine is running or turning over. If you have a code 18 or 19, I suspect that's the problem.

 

I run the code scanner with the FP relay in the circuit and see what turns up. Thanks.

 

Got the problem solved. For whatever reason (no code 18 or 19) the FP relay wasn't grounding through the EEC. The only code I got was 87 (I think) which was a primary circuit fault for the fuel pump relay. I wired in a separate ground to the body and everything works great. But I learned not to ground it through the headlight circuit. If you do that and pull the headlight switch the engine dies. I suspect something is wrong in the EEC, but I'm not ready to spend $80 for a reman computer for it right now. Before I bought the truck the primary battery hot wire to both the EEC relay and the FP relay had shorted and destroyed the fuse link. The previous owner just cut it out of the circuit and never repaired it. He just wired around the relay with the ignition hot that was in the circuit. Who knows what damage might have been done to the computer, but right now everything is working.

 

Sounds like familiar territory. Read my story here.

https://www.ford-trucks.com/forums/1...y-control.html

 

Look over in the battery area, there is a small ground wire that comes off the negative cable and goes around the battery and into the harness. It's the important ground for the EEC and it does like to get corroded, lost, etc. Sounds like you did find a good substitute though, which should work fine.

P.S. Just remember though, the main battery ground goes to the engine block. And then there is a ground wire going from the back of the engine to the firewall/cab sheetmetal. This may be the only ground you have to the sheetmetal, since the cab is mounted in rubber, and the engine is mounted in rubber mounts. So going directly to the battery negative may be a more direct approach for EEC grounding.

 

Thanks. The direct from battery ground goes to the EEC relay and is working. The engine block to cab ground cable is in place. I connected it myself when we put the upper engine back together. I suspect something inside the EEC isn't working as it should, but the work around is doing fine. The only other problem I'm having is that occasionally if you turn on the AC the engine will begin to misfire and die. It only happens intermittently, which is nightmare to try and figure out. All of you have been a great help. Looking forward to many more useful conversations.