I have a 1994 Ranger 4.0 with approximately 330,000 miles. I was driving down the road at about 45 mph and the truck suddenly shut off and nearly immediately an electrical burning smell filled up the cab, no signs of smoke though that I could see although it was dark.

The truck will crank and turn over and it’s lights, radio etc will work but it will not start. So far I can’t locate any obvious signs of anything under the hood or inside the truck doing a quick look up under the dash. The electrical burning smell is still quite strong inside the truck.

Any suggestions or thoughts of any kind as to what may be going on? Any help is appreciated.

 

Spray gasoline or quick start(ether) into the intake and see if it starts, the 50/50 test

If it starts and dies spark is OK, but no fuel
If it doesn't start then no spark
50/50 instant results

The inertia switch is in the passenger side foot well, under glove box on the firewall, it passes power to fuel pump, it would make quite a smell if fuel pump started to fail and draw too many amps


Check engine fuse box for blown fuses
Fuel pump fuse is there

 

I have not sprayed anything into the intake, but I have checked the fuses and I saw none that are blown, including for the fuel pump. Even after a week, the inside of the truck still stinks REALLY bad with the burnt electrical smell. I can’t locate where it’s coming from just by my nose which is frustrating...

 

I will finally have some time tomorrow and over the next few days to dig more into this issue on my truck. Just curious if anyone here has had a burned up PCM before? If so was it producing the burnt smell inside of the truck? To me it makes sense if it was for mine since I can’t place the source of the smell from inside my truck...

 

Well, I found the problem! PCM is obviously fried. I have a new one ordered and coming in on Saturday. Is there any reason to think something else on the truck caused the PCM to fail or is replacing it and calling it a day sufficient?

[img]blob:https://www.ranger-forums.com/8305cc3c-3d2a-4ea8-b9f3-47c7d9c4780a[/img]

 

I tried uploading a picture but it doesn’t seem to be working or showing up for me...

 

The 3 blue capacitors in the PCM can leak fluid when they get older, 20+ years, and that can short out the circuit board

Picture here: Ford EEC-IV

Also Jump Staring to start another vehicle or to start yours can fry electronics
You can use your battery ONLY to help jump another vehicle, so your key is OFF
Using a running engine now-a-days to jump start another vehicle is a roll of the dice, a gamble, it can fry electronics on either vehicle

 

Thanks as always for the info!

I have a potentially silly question. On my new PCM it clearly says “this side up” where the wiring harness connects. However, for my wiring harness to connect properly with grooves etc the PCM needs to be turned in a way that the “this side up” wording will indeed be “down”. Is this critical? My wiring harness that goes into it can’t be flipped to make this work any other way...any thoughts?

 

No, doesn't matter, and never seen that on a Ford PCM

 

Okay, I really don’t have a choice but was curious anyways. Hopefully tomorrow I can be up and running again. This PCM does have Ford written on it but it is also remanufactured.

Thanks again!

 

If it was on the cover then maybe it was for reassembly purposes