Working on an intermittent no start problem, or if it does start it doesn't run for long. This is on a 91 F150 4x4 with 5.0L base options truck.

Turned the key to "on" while probing with a multi-meter, and after a minute or so the fuel pump turned on and stays running during the time the key was in the run position. Both tanks do this and the pumps don't shut off. Now, it comes on anytime the key is in the "on" position.

Today, while having the key in the on position, the pump ran for a couple seconds and then shut off for about a minute and then turned back on. The only code thrown has been a 212 and that was only once. Can't do the KOER test as the truck won't run long enough to complete the test.

Anybody with any ideas here? I'm starting to lean towards a bad (as in intermittent) ECM. Don't want to just shotgun parts but this guy is starting to run me in circles.

 

Bad computer ...common failure symptom.

 

Computer is faulty. The computer is designed so by default the fuel pump circuit is "On" as soon as the computer gets power. Once the computer has started up and is ready to function, the fuel pump is turned off. Constantly running fuel pump means the computer hasn't started.

Usually its bad/leaking capacitors that cause the issue, but replacing them doesn't always fix the problem.

 

Well, it's running very nice now.

Ran a KOEO test with the scanner and it gave me a nice 111. Then started the truck, which I wasn't expecting to happen, it just kept running quite nicely. After a bit I removed the scan tool. Shortly after, the engine started running rough and died. Couldn't get it to restart and both spark testers were intermittent again. Hooked the scanner back up, wiggled the spout and ICM connectors, wiggled the ECM bulkhead connector, and ran another KOEO test to get another 111 code.

Truck started and ran for an hour, so I then removed the scan tool again. The truck ran for another hour till I shut it down. Started it a bunch of times and let it run for a bit or immediately shut it off and re-started right away.

Dark now, so I came in. Any bets on whether it starts tomorrow morning???

 

Egg on the face. Just now noticed I titled this after my furl pumps. duhhh

 

Fixed that for you. rla and Lead are two of the most knowledgeable guys around here, so I would listen to them. You could also check the grounds in your truck, sometimes a bad ground can cause unexpected behaviors.

 

Pull the computer, then open it up. Look for swollen and/or leaking capacitors.

All your symptoms point to a bad computer caused by these capacitors. Very common symptoms.

Bad grounds always a possibility, but most likely computer related.

 

I do not know about Ian, but I am an amateur hack with 40+ years experience. I started on points ignition, carburetored Chevys. Then I was enlightened to Fords around 1979 by a guy with two young daughters.

I remain faithful to Fords, the daughters are a distant memory of infatuation.

 

Honored to make your aquaintence, rla. Been doing this stuff for a bit too. I was 14 when I started dabbling with cars, 65 now and like you I am an amateur. My job was as an electronics technician for railroad signal systems.

Already replaced the ECM and all is fine now. There were two electrolytics that had leaked and corroded one of their leads completely in half. It explains why the randomness of symptoms and how it would wake up when I connected the scanner up to it.

By the way, as I said earlier, my truck is a 1991 and the ECM came out the kick panel instead of through the engine compartment. Took about 30 minutes each way. Just a hint when putting the ECM back into the truck. Take the sealing gasket and spray it with silicone spray and put it on the ECM itself. It will slide into place much easier.

Thanks for your input jla!!!

 

Thanks for the info! Didn't know the pumps were programed that way, would have expected them to shut down with a bad ECM for safety reasons.

Again, thanks for confirming I was heading the right way.

 

Glad you got it fixed and reported back on the cause!