I've had this topic posted in another of the sub-forums for a while, thought I'd make one here to try for a few more views/ideas.

'88 F-150, 4X4, 302, M5~The engine will just randomly die going down the road, sometimes it will come back on but more often than not it is just dead. When it dies, the engine will turn over, all of the electronics work, can't find anything else wrong with it except that the fuel pump won't come on. When it is brought back home on a rollback it will crank up like nothing was wrong, the bouncy ride home "fixes"it. Also, when I replaced the battery last year it wouldn't crank for some time after putting in the new battery. The fuel pump wasn't coming on then too. Every time it happened, I had to have it brought home to work on it until today. I was able to leave it where it sat overnight till I could get to it today.

What I have done~ Replaced the fusible links coming from the starter relay, seemed like a long shot, but they were cheap. Replaced the fuel pump relay and the pigtail it goes into, the pigtail looked kinda ratty. Replaced the ECM (?) on the front of the distributor. The box the ignition switch goes to on the steering column crapped the bed, so it was removed from the equation when put in an aftermarket ignition switch.

I did these tests today~ Part 1 -Ford Fuel Pump Relay Test.
When I jumpered the fuel pump it came on, and everything worked fine after that. I did the rest of the tests, everything checked out good. I did replace the EEC relay for the heck of it. The truck cranked and ran fine to the house.

The fuse block is in somewhat foul shape, I'm wondering if it may have something to do with it. It will be replaced in the next week or two, if for no other reason than to rule it out.

It almost has to be a loose wire/bad connection somewhere, since the bouncing on a roll back cures it for a while. It's pretty aggravating since it just hits out of nowhere. It was odd today that the fuel pump wouldn't come on with the switch, I could hear the relay clicking but no pump humming, until I jumpered it out. After that it was as if there had been no problem.

I'm not fluent in electronics by any stretch of the imagination, I understand the basics but am kind of slow when it goes beyond that. If anyone has any opinions I'd be most grateful.

 

Similar thing happened with my '93 Taurus, it would inexplicably die randomly due to fuel pump not running. After replacing the CCRM (which includes the fuel pump relay), and still exhibiting the same intermittent symptoms, I just ran a new positive lead wire from the relay to the pump. Fixed the problem permanently.

If you go this route, make sure the fuel pump ground is solid as well.

 

That is along the lines of where I think I will be going. Planning to put in a Painless 18 circuit fuse block and run a dedicated line just for the relays. It can't hurt.

 

I reread this and see you pulled a new lead to the pump itself. I have about talked myself into pulling new constant and switch only power to the EEC and fuel relays, as well as running new grounds.Given the way the pump responded to the test, I think my problem is in the relay area.

 

I spent a little time looking it over today, evidently both relays are supposed to have constant power and power from the switch to different terminals on the relay. My EEC relay has switched power to both terminals, no constant power to the terminal that is supposed to have it. The wiring was hacked by the PO, I am going to rewire both power sources to both relays tomorrow.

I plan to put the constant power supply from the starter relay, based simply on the ease of getting to it. I want to put a bladed fuse holder in the line just in case, and I would like a couple of opinions. Should I use two separate fuses, or can I split the line after the fuse and go to each relay? What size fuse would be recommended in either situation?

If anyone has any ideas I would love to hear them. I feel like I have got this nuisance on the ropes, and I am really anxious to get it put behind me.

 

I'd use separate fuses, because then you'll know which relay/component is being wonky in the future if one of the fuses blow, instead of having to track down which one with a single fuse.

 

Didn't think of that, good idea!

 

You said you replaced the fuse links at the stater relay. These two fuse links is what supplies the power to the yellow wires to each relay and not the ignition switch as in the link you posted.
The information in this link is wrong:
Part 1 -Ford Fuel Pump Relay Test.

DO NOT run power directly to the fuel pumps as was suggested above as it is wrong and very dangerous to you and any emergency workers if you have an accident. Can you say law suites.

Make sure the small black wire with a green stripe has a good ground at the NEG post of the battery as it is the ground for the system.



/

 

You are correct, somehow I missed that. On the truck the yellow wire is hot from the battery. On the EEC relay, the black wire with yellow stripe should be hot from the battery right? It isn't, it is hot from the switch only. The PO hacked up the wiring in this area for some reason or another.

I have no intention of running a hot wire directly to the fuel pump, I want to get the wiring for the relays straightened out correctly. As for the ground, i will check it first but I'm curious if it HAS to go to the neg. battery terminal or would any suitable ground do?

I did replace the fusible links coming off the starter relay. My thinking with running all new power wiring to the relays was to (1) correct the wrong wiring present and (2) bypass whatever else has been hacked up that I cannot see. Since my problem appears to be isolated to this area, after pulling a new power source I intended to simply terminate the current source. That should allow me to get power routed correctly without affecting anything else on the current circuit. I hope that makes sense.

 

Yes it goes to the battery side of the starter relay (solenoid). The ignition switch would have no effect on the power to this wire.

Ford has always put the wire on the NEG battery post but in the 90's they used a ground lug on the fender as a ground point and ran a wire to the NEG post for this wire.

 

I forgot to mention that I spliced in the inertia switch (as well as a 15a fuse) when running the new lead. Slipped my mind, it's been a few years.

 

Went out today to smoke the ground over, followed it to a plug with two wires that went into the wiring harness on the radiator support. I guess originally that the one wire on the terminal split into two for the plug. Someone before me had spliced the two into one with a crimp connection, and as luck would have it the black one wasn't in the connection. It was just wrapped around the other, rather loosely at that, and was very green. Redid that and everything looked good. Still plan to pull new power for the relay that is wired wrong.

 

Just thought I would update this post. In the 2 1/2 weeks since finding the loose ground, the truck has not hiccuped once. My son has been burning the roads up in it with no issue.

Many thanks to you Subford. If you ever make it down to the foothills of the Blue Ridge, I've got a Mason jar for you!

 

Today my son left and the truck died. The pumps were running properly but it wasn't getting enough fuel, barely any pressure at the rail. After trying it a few times he said "it sounded different that time", and it cranked. It has the two pump setup, I'm thinking one of them is going bad. I'm betting on it being the high pressure pump.. Is there any way to convert this to a single pump system like the 92+ models, or should I just replace both pumps?