Background: 1990 F350 w/ 460 motor. Mfg'd in March 1990.
Truck shuts off after 10 - 15 minutes, usually at an idle.
There is no fuel pressure during cranking when the truck shuts off (taken fuel line off at fuel filter, input side)
After leaving sit overnight, the truck starts, and there is pressure during cranking at the input to the fuel filter.

Replaced the following parts so far: Distrubutor/cap/rotor/fuel pressure regulator/ECC relay/fuel pump relay/fuel pump relay plug/fuel pump. Checked/manually cycled the inertia switch, but I have not done any electrical diagnosis on the truck yet. The problem was very intermittent at first, but seems to be getting more regualr. We have asked several Ford mechanics, and had it to the local Ford dealership, to no avail.

I will be dropping the tank to inspect the wiring harnesses between the fuel relay and fuel pump.

IMPORTANT: This truck USED to have dual tanks, we removed the rear tank and lines associated with it. This chassis now serves as an emergency services vehicle.

Since it is such an intermittent issue, we are guessing that it is an electrical issue that we just haven't found yet. Yes, I do have a volt meter, and I am getting a copy of the Chilton manual ASAP.

Any ideas on how to better diagnose this issue?

Thanks.

Matt Gehman
Asst. Chief
Barto Fire Company

 

Welcome to FTE!
It might be an issue with the distributor pickup coil. Usually, when they start to go out, they fail when hot.

 

Thanks Ford_Six. I forgot to mention that we already replaced the coil also. Both the fuel pump and ECC relays get very hot to the touch after 10-15 minutes of running. We did not start to have this particular problem until AFTER the motor and fuel pump were replaced. The motor was replaced because of excessive smoking/oil burn, and the fuel pump was replaced because the fuel gauge was not working. Local garage did this work.

Could it be as simple as a bad ground on the fuel pump? Defective fuel pump maybe? I'm grasping at straws at this point. It has to be something that was done during the fuel pump/motor swap. I did not get to drop the tank tonight, we ended up doing other diagnostics on the truck. When the truck shut off tonight, I let it sit with the ignition turned on. After a couple minutes, the ECC relay started switching for no apparent reason. Thought it might be the ECC relay heated up too much, so I swapped it with one I had lying around. Truck started, ran for roughly 1/2 hour, and I shut it off. Then I started it again, and 1 minute into it running again, it shut off by itself. Swapped the ECC relay back, but to no avail. It seems like you have to cycle the ignition for the truck to quit on you. We adjusted the ignition switch (slid the box all the way up toward the steering wheel) and the truck still shut off on us.

We definitely have spark, because when the truck quits, you can get it to run on Ether. For some reason, the fuel pump will not pump more than the initial prime when the truck is not working.

PS: When the truck quit tonight, I had 14 V on the one leg of the Fuel Pump relay, 7 V on the other. When the truck was running, I had 14V on both legs.

Thanks for your help in advance!

Matt

 

Ok, some good info left out the last time around. When it dies and you try to restart it, the fuel pump runs when you first turn the key on, then stops, right? Next time it dies, remove the gas cap. If there is a vacuum in there, that is your problem.

 

Ford_Six,

Again, I apologize since it seems I have forgotten to include some other items:

We took the gas cap off multiple times, no vacuum.
We also replaced the EEC Microprocessor, twice.

Sorry to leave out these things, it's just we have tried so much, I can't remember it all in one sitting.

You are correct, the fuel pump runs for about 2 seconds when you turn the key to the "run" position ( and we get fuel @ the filter) , but we get no fuel through the line when cranking the truck. When the truck runs, we get fuel through the line when cranking the engine.

We appreciate your help on this.

Thanks.

Matt

 

Replace the fuel pump, sounds like you may have replaced the fuel pump with one from an auto parts store. Get one from Ford.

Another poster on another Forum on this site had the same problem with the same voltages with a pump from autozone I think. He replace it with one from Ford and it fixed his problem.

 

Subford,

The current fuel pump is a Ford fuel pump. Maybe the wrong one, from what I'm gathering? Ford took all kinds of numbers to try to determine the correct fuel pump for this truck, it seems even they were not sure which one to put on.

Thanks, we're still debugging. Found the connector at the inertia switch was semi-melted when I took that off to check. Something was/is heating up.

Is there any chance you can point me to the other thread you spoke of in your last post?

Thanks.

Matt

 

Hello All.

Well, we seem to have our problem resolved. We took the truck to a Ford Dealership in Reading, PA (Manderbach Ford), and they diagnosed a couple things:

1.) No codes in the computer, diagnosed bad computer module. (one under the dash that goes through the firewall)
2.) Aftermarket pickup on distributer - replaced with Motorcraft part
3.) Replaced spark plugs with Motorcraft
4.) Replaced module on the driver fender (aftermarket module) with Motorcraft part.

Evidently, this all stemmed from aftermarket parts. What I was told by the mechanic up there is that the aftermarket parts do not have sufficient grounding in them, thereby introducing positive feedback into the ignition system, and burning out parts. We actually had 2 symptoms to this problem, we had intermittent spark/fuel problems.

Thanks to all who provided feedback to us. We finally got it fixed!

Matt

 

Glad you got it fixed, I was just reading this and it sounded like a grounding issue to me too.