The title sums it up, Started up my ranger, took off down the road about a quarter mile later a burned/hot electrical smell took over the cab without any smoke, the truck sputtered and died. Towed it back to the house and did some googling only to come up with squat, so I began doing what little I know how to do.

Checked the relays...Found that all relays are good, There is power at the pcm relay, and it clicks, however no fuel pump or coil power.
Read up a bit on that and odd and end forums from different manufacturers all suggest that the pcm/eec has burned up. However everything I have read says that my computer is located under the hood behind the vac/master cylinder, so this is not what I was smelling...Or is it possible.... Ive started pulling the dash apart in hopes to find a bad ground or melted wire jacket....So far nothing however it is still in progress...

Any ideas or anyone with similar issues, any input would be a blessing.

Thank you in advance.

1994 Ranger XLT 4x4 4.0L

 

EEC relay(PCM relay) passes power to PCM, fuel pump relay, fuel injectors and coil from a 30amp fuse.
If you pull out the PCM relay, with key off, one of the slots should have 12volts, thats the power from that fuse, 24/7 power(always on).
When you turn the key on ignition switch sends 12v to this relay to close it, which then passes that 30amp fuse power to above devices.
So this relay can still "click" but have no power to pass if that fuse is blown.

Fuel pump relay also passes power from another 30amp fuse, if you pull out FP relay it should also have a slot with 12volts 24/7

If you smelled "magic smoke" but didn't see it then I would look in engine bay more than cab

Could be a problem under the engine fuse box.


With key off see if headlights, parking lights, tail lights and Brake lights still work

With key on see what doesn't work, turn signals, radio, blower, ect............

"Doesn't start", ???

Starter motor doesn't work?
Or engine does crank but won't fire up?

 

sounds like a fusible link burned up

 

Something else it could be, is if you put the wrong size fuse somewhere, in either the mass distribution box or the driver's side kick panel, either by accident or intentionally. Of course, the bigger fuse won't actually do anything until something goes wrong. Thus the bigger fuse doesn't (usually) blow, causing wires to melt.

To elaborate on the fusible link that Cheese_man suggested, you're lucky that your truck didn't melt down. Usually when one wire melts, the others in the harness around it melt too and it all goes to hell in a hand basket real quick.

However, fusible links are specifically designed with that in mind. The wire inside melts, but the coating doesn't melt thus the link breaks and no further damage happens. Fusible links are usually around the positive battery cable. Take a look at those. Also, follow your nose. If it smells like it's burnt it probably is burnt.

 

i helped a man many years ago with this very issue

only took me 30 minutes to find the cause

the alternator failed ( overcharging ) cooked the battery ( internals exploded ) and burned up the fusible link

that what the fusible is designed for , to blow if and when the alternator fails and floods the electrical system with excess amperage generation

but that time the alternator took out the battery as well

 

^ Ah, so that's what they protect. I wonder why they simply didn't use a maxifuse instead. Oh well.

If it took out the battery in this case too, that would explain why the truck doesn't start.

 

yes and no

the fusible link is the direct connection in older vehicles to the main fuse panel

it is like a older version of today`s circuit breakers, they trip faster than fuses blow

he should have the battery and alternator removed and tested

 

Agreed. Hopefully for his sake it's something relativity inexpensive like the links.

 

You should also check the wiring around the connectors and thermostat area.

 

Went through and checked a few more things because of the great advice, working on the wiring in the bottom of the distribution box...there was a short or bad connection in the wires for the fuel pump relay that I never put any stock into, just thought I needed to clean the terminals because it would start if I just wiggled the relay, (Prior to the burnt smell and death stall) however I'm still looking for the burnt wire smell under the dash...so far no wires appear to be damaged. The starter rolls the truck over just fine. The battery still has proper voltage being I haven't been cranking the heck out of it. im going to keep plugging away at all possibilities. Thanks for all the suggestions, I've got more reading and investigating to do. I will be sure to post the solution as soon as I find it. Til then I welcome any and all advice or experience.

On a side note, would the smell of a bad eec/pcm smell the cab up being it's located under the hood on the opposing side of the firewall?

 

it could since the PCM is located very near the air intake for heater core box

private message RON D , he has more experience on how to trouble shoot the PCM receiving power

 

There's one other module right inside the cab, I believe this is the RCM computer. It's underneath your black cup holders. To remove it, take a BF screw driver and turn the keys inside the cup holders to release. A little wiggling and it should come right out. It can be a bit tricky.

 

I trailed that issue down on my 94 ranger took me 1 hour to find the culprit I hope it helps in my case a blown capacitor in my ecu controlling the fuel pump mine would still fire off ether but would die promptly and pump wouldn't run

 

"Holy Smokes Batman"

Thats one fried PCM

 

Thread bump! I experienced nearly the EXACT same scenario a few weeks ago with my 94 4.0 Ranger as described by the original poster here. I’m curious about this PCM here, did you also smell a burnt smell coming from your inside your cab before finding this?

 

Found my problem...

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