91 Explorer EEC Relay fuse keeps blowing?

[goldeneagle]

Hello Everyone

Dan here. My 91 Explorer with a 4.0 L Engine keeps blowing the EEC Relay fuse. This happens when the engine runs for a minute to 2 minutes. I've changed the EEC Relay, Fuel Pump Relay, and the Electric Fuel Pump. I've also inspected all the wiring and can't find any shorts anywere, I'm at my wits end. Does anyone have any ideas on what could be causing this?

Thanks in Advance

Dan

 

[MrShorty]

I've also inspected all the wiring and can't find any shorts anywere,

All the wiring? That's pretty impressive, however, I have my doubts. I have to think that if you had inspected everything, you would have found a short. I would suggest starting again and make sure you do inspect everything.

Question: Will it blow the fuse after a couple of minutes key on engine off (KOEO), or does the engine have to be running for it to blow? If it blows KOEO, then unplug everything that gets power from the EEC fuse (be sure you have a wiring diagram, there are several circuits that get power through that fuse) and plug them in one at a time until the fuse blows. 1st step in this kind of diagnosis is to isolate the fault to a single circuit feeding off of that fuse.

 

[goldeneagle]

Reply to Shorty

Hello

Dan here. No it doesn't blow the EEC Fuse when the key is on without the engine running, only when the engine is running for a maximum of 2 minute will it blow the fuse.

Thanks

Dan

 

[MrShorty]

That complicates it a little. It also suggests that the fault might be intermittent, which may be why you didn't find it while inspecting the wiring. So you'll have to leave enough plugged in (like fuel injectors, ICM, and such) that are necessary for the engine to run, and unplug those that aren't necessary (like the transmission connector).

This is an interesting problem.

 

[paulvaneck]

Same Problem

I have the same problem. I have a 1994 explorer. Did you find a solution as it is also driving me nuts.

 

[db1969@aol.com]

I have the same problem with my 1994 ford explorer but mine is blowing with KOEO.Key on Engine Off, as soon as i turn the key on, POP IT BLOWS,

 

[arco777]

You'll need to trace some circuits with a wiring diagram and look for a short to ground.

Whenever you turn the key on, the EEC relay switches on. That completes a circuit (through the fuse) which likely has a short somewhere. You need to trace that power circuit in both directions. Use a multimeter and check for the completed circuit shorting to ground somewhere.

If you need more info let me know, I can research some wiring diagrams for you.

 

[Trickdaddy1980]

1991 explorer

All the wiring? That's pretty impressive, however, I have my doubts. I have to think that if you had inspected everything, you would have found a short. I would suggest starting again and make sure you do inspect everything.

Question: Will it blow the fuse after a couple of minutes key on engine off (KOEO), or does the engine have to be running for it to blow? If it blows KOEO, then unplug everything that gets power from the EEC fuse (be sure you have a wiring diagram, there are several circuits that get power through that fuse) and plug them in one at a time until the fuse blows. 1st step in this kind of diagnosis is to isolate the fault to a single circuit feeding off of that fuse.

I was having the same problem with my truck. Chased the wires going down to transmission from driver side fender well. The wire harness had got into exhaust and caused a dead short when the vehicle would hit a bump in the road. It took me two months and a stack of fuses that I purchased from my local junkyard. Fixed the wires, reroute them away from any potential threat, replace fuse 1 more time, and enjoy your Ford!

 

[Maniak]

I was having the same problem with my truck. Chased the wires going down to transmission from driver side fender well. The wire harness had got into exhaust and caused a dead short when the vehicle would hit a bump in the road. It took me two months and a stack of fuses that I purchased from my local junkyard. Fixed the wires, reroute them away from any potential threat, replace fuse 1 more time, and enjoy your Ford!

That is the most common place for one of the ECU powered line to short, at least if you have an automatic trans since the ECU is sending power to the TCC and 3/4 solenoids.

~Mark

 

[smegun]

removed fuses my fan blower relay pin 86 and 85 and my abs pin 85 are short what is the purple orange stripe wire and blue pink strip wire any one got the rout or skematic handy


tested relays 3 of the 6 were tacky I banged em on my desk and they work but I think that the short has scored the contacts id open em up to clean em if it was easy but before I buy new ones I want to run through the wiring to see if I got a dead short I have ignition but my battery is being pulled down to less than 4 volts at a 10th of a volt a second ive had intermittent fuel pump failures also the main code for these is FOAB-14B192-AA with some differences in manufacturer numbers on the bottom my fear is that one of these are in the wrong order .... I can only see that
one has pin 87a in use but most only use 4 pins or 87 alone

 

[Neighborsboy]

Hello all,

I know all of these posts are old but I need HELP! My 1991 Explorer keeps blowing the EEC fuse and I can not figure it out? Any more ideas other than the one mentioned above?

Thanks in advance, "Be Easy!" Neighborsboy

 

[FR-425]

It's a short. Now to find it.

First I would check to see if the truck has an after market alarm, if so remove it. It may have an ignition kill circuit and may be faulty. With that removed you can eliminate that.

(many times we get "no start" and "blown fuse" problems on here and the OP forgets to mention the after market alarm.)

The most common one is the transmission harness. Not easy to fully inspect as it runs over the top of the trans. Best to disconnect it from the trans and pull it out from on top of the trans to get a good look.

It's also possible that one of the shift solenoids is shorted. To test that just pull the plug off and check for continuity from each pin of the solenoid to ground.(trans case) of you get 0 ohms on either pin it's shorted.

Then check each pin of the harness wires to ground. same deal 0 ohms = short.

If you find a short on the wire harness you will need to dig it out to find the problem.

The harness getting pinched between the trans and the floor pan can be caused by bad motor mounts and or trans mount allowing the engine/trans to lift and pinch the wires. So if the harness is pinched you will need to correct the "cause" or you will be doing it again.

Disconnect the battery when looking for shorts!

 

[knuckles g]

Thanks - I found a wire near the transmission that had been touching the exhaust pipe which melted the cable sleeve and the insulation wire, leaving a bare area which would occasionally short and blow the eec 30 amp fuse. Fixed it. problems gone

 

[Bob Weigel]

I was trying to figure what 'blow' meant. ie. did the coil blow like the one '91 I'm working on here or did the contacts fry/cease to conduct? The fuel pump would run all the time/run down the battery I"m told on this one but the middle brown relay was open is the first fault I discovered....hmm