Okay, '92 F250 with the 5.8. I replaced the throttle position sensor in attempt to correct a rough idle and improper up-shifting at low speeds. Had to remove the throttle body to do it. After I put everything back together I fired it up and it was running beautifully. I sat in front of the engine just watching and listening for a couple minutes when all of a sudden she died, just cleanly shut off. When i attempted to restart it I noticed that the fuel pump was not turning on and there was a burnt smell in the cab of the truck, Great! I ran through a couple of the tests in the Haynes manual like trying to ground the fuel pump lead on the EEC to try to engage it, but it did not prime the pump, power values at the harness on the tank was good. I've inspected visually for burnt wires under the dash and found nothing. Fuses in the fuse panel all look good as well as all the fuses and relays in the distribution box. I decided to hook my code reader up to it and see if it had any clues for me, only the EEC will not initiate a self test! The motor turns over, the dash lights up, virtually everything works save for the fuel pumps and the EEC won't do a self test. Also the EGR sensor has very low voltage according to the tests per the haynes manual. I'm lost!

 

Noticed not too many folks reply to the threads regarding electrical problems, someone must know something! Please help, I rely one this vehicle to get to work and its dead in the water right now, cant afford to tow it cause I live in the sticks!

 

It sounds like the PCM Power relay is not picking for whatever reason.
That means you are not getting power to the Ignition coil/ICM either.

That all comes from the Ignition switch.
So the Ignition switch is not relaying the power to the wire 16, a red wire with a light green stripe.

You will have to check the plug on the Ignition switch or the switch itself.

Check fuse "U" in the engine compartment distribution (fuse/relay) box for power with the key on:


/

 

Where is the ignition switch located? How to check fuse for power? If the ICM wasn't getting power would the truck still be able to turn over?

 

On top of the steering column down near the floor board under the dash.

Using a test light. Turn on the key and ground the clip of the test light to a good ground. Then touch the point to each side of the top of fuse "U" at the little bear place. See image below. Both sides should light the test light.

Yes it would still crank but not start.

Testing Fuse:


The test light:


Using it:

/

 

Don't have a test light, can I test the fuse with a volt meter? I've just run the ignition coil resistance and coil supply voltage test from the Haynes manual and all are within acceptable values. I'm moving to the ignition switch per your suggestion now

 

The fuses you suggested all check out great. What next?

 

I was not talking about testing the fuse, I just wanted to know if it had power going in and out of fuse "U".

Meters are not much good for checking the Ignition and fuel system.
If you a meter say you have power that does not make it so. If a test light with an incandescent (not LED) bulb inside says you have power you have power.

I have no idea what a Haynes manual says as I would not have one.

 

I can confirm that everything in the distribution box is receiving power and functioning properly. I suspect my PCM might be worth finding and giving a sniff. Where can I find my PCM?

 

I though that you said you bypassed the PCM by grounding Pin #6 of the self-test plug with the key on and the fuel pumps still did not run.

Anyway it is located in the drivers kick panel. You unplug it from under the hood. Pry open the inter fender with a broom stick after removing the screws.
Unplug the the computer with a 10mm socket then remove the two nuts, one above and one below the plug and pull the PCM out.



/

 

Thank you for the info subford. Yes I did ground the fuel pump pin in attempt to engage the fuel pumps and nothing happened. I also hooked up my code reader to the DLC and nothing happened. But I took my meter to every fuse in the distribution box including the diode, and tested the relays and all checked out fine. After reading on some more threads I'm thinking my PCM burned up. Any idea what causes this? I'd hate to buy another PCM and hook it up only to have it short out again.

 

Even if the PCM is burned up if grounded pin #6 and turning on the key and then the selected fuel pump did not run then you have other problems also.
Lets get that fixed before diving into the PCM.

Does the PCM Power relay click when the key is turned on?
Do you have power on the red wire going to the fuel injectors with the key on?

 

Yes the relay does click when I turn the key, I will check the said wire to the injectors