Hello guys, I desperately need any inputs I can get.

I started my truck tonight (1994 F250 4x4 460/E4OD) to bring it to my newly acquired garage and it started fine, and idled fine for about 10 seconds but it abruptly died.. as if I turned the key off. No bogging, just died immediately. Go figure, it couldn't have died *after* I brought it to my shop. Here is what followed:

Engine cranks at normal speed but would not even try to start.
I could no longer hear the loud buzz of the fuel pump when turning the key to the on position. The warning lights on the instrument cluster still come on, and all of the accessories work fine.

I immediately smelled a distinct burning electrical scent in the cab and under the hood. I found this very strange, immediately began feeling for heat under the dash/hood around all of the wires and inspected the wiring, but nothing felt warm or looked out of the ordinary. Something definitely burned up though, it smelled horrible.

I checked for spark to the plugs, none.


This happened after dark and it has been raining heavily nonstop for 2 days, so I didn't get to check much else just yet. Tomorrow I am going to be testing a few different things, try to pull codes, and checking fuses.. but I figured I'd make a thread to begin gathering your opinions and potentially narrow this down. My biggest concern was that burning smell. Strong odor in the cab however a strong odor in the top right of the engine compartment near the fuse boxes, relays, PCM & ICM as well. What could burn up that would make the fuel pumps not turn on AND create no spark? PCM?

PLEASE, if you have any suggestions at all I'd really appreciate your input. Thanks a lot.

 

Try pulling codes from the ECU, If you cannot then ECU most likely smoked and needs replacing.

 

2X^^^

What happened is the grease has dried out in the PCM plug and the rain got into the PCM plug and shorted it out.

The PCM is bad as it let out the smoke.

 

I kind of figured that. I'll go try to pull the codes and let you know what happens. Also, I may try to pull the plug out of the PCM and inspect for a burnt appearance.

If this does end up being the culprit, are the PCM's for my truck hard to come by? I really hope there is some kind of a part number still visible on the PCM when I pull it out, because the engine in my truck is not original to it.

Thank you very much.

 

I just tried pulling the codes. Upon the first attempt with a length of wire from the negative terminal to the EEC test port, I heard a couple strange clicks, and the check engine light would NOT blink the codes as it normally would.

I shut the key off and tried again, this time in the ON position the check engine light stayed on constantly (no blinks) and now instead of the fuel pump not coming on at all.. the fuel pump now stays on and makes noise constantly in the ON position.

Next I think I'll unplug the computer and inspect it for leaks/burn marks/moisture and let you know what I see.

 

Unplugged computer, I did not see any burn marks however there was a bit of water inside the plug, as well as some strange looking green slime on some of the pins. The truck will start after about 5-10 seconds of cranking, however it runs very poorly and shuts off after about 5 seconds. Since the engine has been changed to a 7.5 (VIN indicates a 5.8 as the factory engine) I wasn't surprised to find that the computer in the truck is to a 1994 F250 with a 5.8 and E4OD, (OE # F4TF 12A650 PA). Oreilly Auto has a remanufactured unit for $130.00. Are the aftermarket remans even worth it?

 

That's weird the truck even ran correctly, given the PCM isn't for a 7.5, which is calibrated for 19lb/hr injectors for a 5.8. The 7.5 has 24lb/hr injectors....

Since you said that fuel pump runs continuously now and the CEL stays on, I'm leaning towards the PCM failure.

Also, check the relays for the Fuel pump and the EEC(PCM). Be sure they aren't toasted in their sockets.

 

Thanks for the input. After thinking about it more I thought it sounded a little strange.. 5.8 computer running the 460 as well as it did. Actually it ran rich, however the truck has no O2 sensor.. don't know why that sounded like a good idea to the previous owner. I would like to maybe try getting a computer for an actual 94 460 truck? If the big block ran with the small block computer then it must run with a big block computer.. but Im not sure if the wiring harness would allow it. Could anyone tell me if that would work?

Also, I pulled out every relay and none of them appeared out of the ordinary. Definitely sounding more and more like the PCM.

 

Bump. I am unsure if the wiring harness is a big block harness with a 5.8 computer or a small block harness with a 5.8 computer. Can anyone tell me if a 1994 7.5 computer would work with a 1994 5.8 harness (if thats even what it is). Wondering if I should just buy a replacement of the 5.8 computer that was already in it since it ran fine?

 

The harness connector is the same for the 300, 302, 351, 460. All are 60 pin.

If it were me, I would buy the correct PCM for the engine and transmission combo.
Like I said, the 7.5 has 24lb injectors and the 5.8 uses 19lb injectors.

Also, the previous PO leaving the O2 sensor out is probably why the 7.5 ran. It allowed or fooled the system so that the injectors ran at max. So the PCM had no control over pulse width or duration.

 

Thanks for the advice. That is the conclusion I was leaning towards as well. Would an aftermarket PCM be worth my time/money or should I hunt down an OE unit?

 

There really isn't aftermarket....
Remanufactured PCM'S are all that are offered unless you mean a reman with Moates or QuarterHorse to tune it with.

Get the Reman version for the engine/transmission combo, and plug it in. And the sooner you get plugged in after leaving the parts store, the better. Need to know if it's working or not and also take pics of the current PCM.

 

Guess I worded that wrong, yeah I meant the remans, not aftermarket.

I'll get the reman for a 94 460 E4OD and hope for the best. Provided it fixes the issue I hope it atleast runs well enough in open loop considering there is still no O2 sensor yet.

 

After plugging it in, run the KOEO test.

You want to it communicate and show 11 or 111.

Anything that shows its working.

 

You need an O2 sensor installed to stand any chance of running correctly.