88 F150, 302, manual 5 speed, single fuel tank. The engine will randomly cut off while driving, all electronics keep working other than the fuel pump. Some times it will start cutting out and sputter, or go completely dead for a moment, only to start right back to running. It has stranded me twice and had to be towed back home. As soon as it was off the roll-back it fired right up and ran.

I have replaced the fuel pump relay as well as the pigtail for it. The fuse block is in rough shape and I have been planning to replace it. Other than that my only thought is a loose wire or loose ground. The fact that bouncing around on the back of a wrecker "fixes" it is killing me, I cannot troubleshoot it until the problem presents itself and the side of a highway at midnight is no place for that.

My plan is to start at the in tank fuel pump and work my way forward looking for anything loose or broken. After that I don't know which way to go. If anyone has any experience or advice I'd appreciate it. I love this truck, but it has got to the point that if I can't be sure I've fixed it I'm going to have to buy a newer one.

Thanks in advance

 

Welcome to the forum, Goat!!!


I had one do this and it was the pick-up in the distributor. Took me forever to figure it out. it would run then start slowly dying and you could smell it being really lean. The ECM uses the signal from the pick-up to verify that the engine is running to keep the pump running. If no signal, it will shut down the pump after a couple of seconds.

Here are the top 3 items I would check first

1) The actual ignition switch on the column. They are bad about the the 4 metal ears that hold the plastic guts in them working loose causing a bad connection in the switch. (Was a recall for this years ago)

2) The TFI module on the side of the distributor. It works with the pick-up to relay info back the the ECM They often get hot and fail over time, then after cooling, will work again for awhile.

3) The distributor pick-up inside the distributor as mentioned above.

4) Check the harness at the pump area. Make sure the ground connections are good.

5) Check the body and chassis grounds to the engine and frame. A bad ground can cause all kinds of problems.

6) A bad fuel pump motor itself.

Good luck

 

Thanks LXMan! I've already had a run in with the ignition box on the column, I replaced and redid that last year. I will check out the pick up coil, hadn't thought of that.

I believe it's somewhere in the wiring for the fuel pump itself. When it quit, turning the ignition on I could hear a relay click but the fuel pump wouldn't prime. I did put my test light on it right then and had power coming into the fuel pump relay, but I couldn't get to the connector on top of the tank where I was.

I plan to tear into it tomorrow, starting at the fuel tank working forward.

 

Went through a few things yesterday. Checked over the in tank pump, everything appeared to be good. The pump that is going off is the one on the frame rail. I tried to chase it down to see where it is getting power from, but had no luck.

I remembered something else that happened related to this. A few months back I put in a new battery, and replaced the starter relay on the fender well. I did all of this in the parking lot at the parts store. After I had hooked everything back up it did this exact same thing, the pump on the frame would not come on. At the time I thought it had to be a bad connection on one of the wires coming off the starter relay, so that's where I focused replacing the eyelet connectors. It wasn't an immediate fix, but after a little tinkering it started back up.

Looking at those same wires yesterday, there are four of them, I realized they are fusible links. I do not know where they go or what they feed, but I wonder if maybe they haven't gone bad and are interrupting the power supply to the pump somehow. I don't want to be taking shots in the dark hoping for a fix, but as these are cheap I'm going to put new ones on anyway. Thoughts?

 

Sounds like a plan. My dad's 89 was having issues with fusible links. I ended up replacing them with inline fuse holders using 30amp blade fuses. Once a year or so, it will blow the fuse and I have never figured out why. He just keeps a pack of fuses in the glove box.

You may have one that is partially broken and has a bad internal connection, but I would think that they are wired in before the relay, so if you have power into the relay on the coil terminal and the power in terminal, then I don't think it is a fusible link. You might want to check the inertia switch under the dash too.

 

LXMan, Thanks for the reply.

Those wires were indeed fusible links, I clipped them out and replaced them. I did get a new pickup coil, but when I realized the distributor would have to be taken apart to replace it I decided to go with a new distributor instead. I know me, with limited time to wrench I would wind up mangling it.

The inertia switch has crossed my mind, but it appears to be working. I'm not sure on how to check it exactly. I learned how to work on things from my Dad, but he never let anyone but himself work on anything electrical.

Thinking on back on that makes me laugh now. I was a millwright for @ 10 years, building, installing and maintaining huge machinery. For another 10 years I built precision tooling and lifting devices of all sizes and weight capacities, some up to 60,000 lbs. For the last 5 years I've been in charge of 4 steam driven generators in a paper mill. My units make a total of 65 MW and I am the one who starts them up, shuts them down, syncs them into the grid and makes sure everything in general is well and good. All of that and I have never learned ( never made time to learn is more like it ) how to use a Fluke meter.

Sorry for the tangent, it just struck me as funny.

 

I am mostly self taught myself as well. I did take auto mechanics in high school vocational school. I was blessed with being mechanically inclined which has saved me tons of money over the years being able to repair my own vehicles. I have been in industrial maintenance for over 20yrs now. Luckily I have learned to use my Fluke meter over the years

Good luck, maybe repacling these items will fix the problem.

 

Back at it again, it hasn't been on the road much the last couple of months but when it was it gave no problems. Now all of a sudden it has quit twice in three days. After the first time I was able to get it running and replaced the ECM on front of the distributor. The last time was yesterday, and luckily I was able to leave it sitting overnight to troubleshoot it.

Since when it quits the fuel pump will not come on, I did these tests to try to find the problem Part 1 -Ford Fuel Pump Relay Test.

Everything tested out good. When I jumped out the plug to test the fuel pump, it started working again and the truck was fine after that. Would crank and run without any issue. I did not do any tests on the EEC relay lug, when the truck started I forgot all about it (just got off the graveyard shift). I did put a new EEC relay on just for the heck of it.

I'm thinking it has to be something in or associated with the relays. Any ideas?