Electrical problem - Fuse 8 in Power Dist. Box blows - How do I find the fault?

[LuvMyRig]

:exp: My ride: 1992 Explorer 4.0L V6 pushrod with AC and 4WD

My engine shut off while I was driving, about two miles from home where I had left. It died without warning or sputtering, radio and lights still working. I tried to start it again, and the engine turned over but would not start. I got it towed home.

I figured that the problem was electrical because lack of fuel somewhere would have caused sputtering before dying. Sure enough, I checked the fuses, and Fuse #8 (30A) in the Power Distribution Box was blown. I replaced the fuse, and tried starting the engine. The engine started and ran for maybe ten seconds, and then died again. I checked the fuse that I just put in and it had blown.

So, apparently I am drawing too much current through this fuse. I checked the electrical schematic for my ride (Haynes, page 12-23). This fuse provides +12V to about two dozen different components through the EEC Power Relay: ICM, fuel pump relay control, fuel injectors, IAC valve, and the PCM, along with a few other components.

How do I start troubleshooting this fault with so many parts to check? Which parts should I check first and how do I check them? Also, where in the engine compartment is the EEC Power Relay? It is mentioned in my manual only in the schematic, and I am having a hard time finding it.


On a side note, I measured the resistance between the power cables after I disconnected them from the battery, and the meter read 0.00 ohms. I know that this has to be wrong because that would have blown my battery when it was connected, and the battery is fine. I tested the meter with known resistances, and got reasonable measurements, so what am I missing here?

 

[robertliana2]

Did you ever solve this issue? Mine, also a '92, is doing the same thing.

 

[Anime]

The EEC relay is also located in the power distribution box under the hood, it should be clearly indicated in the fuse/relay diagram under the distribution box cover.

It could be something as simple as a stuck/fried EEC relay, the first thing I would suggest is replacing that relay. It's fairly common for both the EEC relay and fuel pump relay to go bad, especially with high mileage. It's a REALLY good idea to keep spare relays and fuses in the vehicle, a cheap way of doing this is grabbing all the relays and fuses out of other Explorers/Rangers and similar Fords in salvage yards.

There could also be a wiring short, do a visual inspection with a flashlight of all the wiring going to and from the distribution box, check the battery cables, fender relay cables, etc. There might be a wire that is close to some metal that cut through the sheath and is shorting out. You could also replace the fuse again, and have someone start it at night in the dark with the hood up. If you see a spark when it starts and then dies again, that will show the location of the short.

It could also be the PCM, when the capacitors in them leak, it damages the electrical traces and can cause electrical issues. You can take off the PCM cover and look at the 3 cylindrical caps to see if there's any leakage under them or damage to the board.