Missing connection

A little back story... wheeling last weekend, swallowed water, a lot of water. Didn't hyrdro lock the motor, and it got out of the hole under it's own power, didn't stall out or anything. On dry land it ran even worse and I pretty much had it pushed home. Left her for the night to dry out...

Barely ran in the morning, everything was still pretty wet. Played with it, took the cat off (maybe clogged from water, no idea), checked for spark. Wasn't getting spark from the coil. Cleaned the MAF, threw in a new coil, some spark, checked the ICM, good. But now when it ran I noticed quite a leak on the block where it used to be a pinhole of coolant, is now a decent drip. Time for head gaskets... Left the original problem at that.

Did a head gasket job by the book, dotted my I's and crossed the T's, ducks all in a row. Checked compression and it's between 165 and 175psi. Without even running the motor (I noticed the permatex beads on the new gaskets, so they need to heat up and what not to seal completely.) Put everything back together right, and even painted my valve covers blue to match my suspension.

Cranked it over... and nothing. Starter turns, motor wants to catch, at least one cylinder was firing (smoke out the Y-pipe, cat/exhaust disconnected). Can smell gas so I know it's getting fuel, and of course it's getting air.

Now the real mind bender. During the tear-down, on the wiring harness that has the injector connections, running back down to the firewall off the motor with a little bracket on it, there's 4 pigtails on the end. 2 for the O2 sensors, one that meets up with the speed sensor/reverse switch, and another one. It's a 2 pin connector, that is perfectly clean, like factory clean. I can solemnly swear up and down that I didn't disconnect it. The wires going to it are Purple/Yellow and Orange/Yellow. It's a more-so circular connector.

Running through wiring diagrams, wearing out the multi-meter, and searching the web, all I can find is possibly a octane adjust shorting bar, or a torque converter/gear sensor. Should that even be there? Also this truck is a 5 speed, and doesn't have an EGR system.

Maybe I can get some pictures posted up.

On this diagram:
http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Enginecontrols4_0_3_0_2of3.JPG

(middle left in diagram)
The P/Y and O/Y are for an automatic so not used in the 5-speed

Have you tried some starting fluid(ether) to see if it fires up on all cylinders.

Any possibility you are running a water/fuel mix now
Any water would be sitting at the bottom of the tank now, so first to be sucked up by the pump.

I had forgotten to mention that it has no spark to 2 of the coils, the middle 2 cylinders.

Why would I have that connection on a naturally manual truck? And why would the cap on it JUST fall off now when I'm having problems? Anyone else know of possible connections down there?

The truck had at least ran before the teardown, just on 2 cylinders (pulled plug wires off, and only 2 of the cylinders, which aren't the ones missing spark now, stopped working at that point). I figured it was a lack of compression making the difference.

My '94 with 4.0l and 5-speed has that wire as well, with cap on it.
I assume it was cheaper to include the wire than have two separate harnesses.
Dunk in the water might have done the cap removal for you.


The coil is actually three 2 port coils, you can test them with an OHM meter.
The coils are fired by Grounding, so one coil fires and spark goes to 2 spark plugs, this is called a waste spark system.
The wiring for the coil will have one 12v wire and three Ground wires, one for each coil.
The three ground wires comes from the PCM, so are not grounded until the PCM grounds them.
The 12v wire will have 12v when key is on.

Fuel injectors work the same way, they have 12v when key is on, then the PCM Grounds the injector to fire it(open it)

It fired right up yesterday and runs on 2 cylinders. Now i know im chasing a short in the wiring. Spent a while checking for a ground short and then figured out i did it wrong by using the motor ground strap. Although it shouldn't make a difference because its going back there any how...

That missing connection... i put a jumper wire on it and it started up. Ran just the same (like shit) without the jumper.

#2 and #5, the middle cylinders get no spark at the coil, and the #4 and #6 get spark at the coil but no fire. I tested the plug wires and they are good. Had advance auto check my ICM and it came back good.

Tore into that harness after wiggling the whole thing some, it got connection. So the first thing I noticed was electrical tape, all over. Someone was in there before. A couple wires had splices in them (nothing crossed, likely break repairs).

The wire at my coil which was an open circuit was rubbed through, then corroded completely, and some other wires were abraded. One wire with a shielding on it had the shielding water logged... There's my problem. At least the most of it.

This was after 17:00 so the ford stealership's service/parts dept. wasn't open. Tomorrow I will stop by and see what they can do for me. If the price is right I will completely replace that harness (injector clips broken, wires just old, new one won't hurt). If the price is way too high, I'm going to repair the old harness. Granted no matter how well I repair it, a splice will fail and it'll have to be done again. At least this way I should get another 20 years out of it.

Ok, so it looks like im fixing it for now. Should have my old girl running like a champ tonight.

It ran for 2 days then blew the driver side head gasket. H
failed from a coolant port to the middle cylinder. Machined the heads and put it all back together. All in spec again. This time... it ran for 30 sec, killed the motor to add water, ran for another 30 sec, killed it again. It wouldn't fire up again. Checked the oil and had quite an excess. Drained a lot out and took a sample. It has a LOT of gas in the crank case.

Blown rings? Cracked block? Wtf? The motor is scrap now any way.

Update: had a buddy of mine take care of her while I went to boot camp, he found a mechanic to do a motor swap for cheap. I heard it was an exploder motor with about 80k on it.

Mech can't get it to run. I talked to the mech today and he said that he threw a crank sensor, cam sensor, intake swap (had to use the ranger upper), but it just won't spark. He reused the wiring harness that I rebuilt (and tested, fully), since the exploder was different.

I'm thinking the ICM or ECU is fried. Previously I had the ICM tested multiple times and it was clean, popped the cover off it and the internals are 100%. Narrowing it further to the ECU. Problem? Where in hell is the ECU on this truck? Every source I've found says that it's here or there, and I have nothing of the sort.

So, opinions? And who has ACTUAL pictures of the location of a 94, 4.0l, 5 speed, 4x4, Federal emissions ECU?

The PCM in your truck is mounted in the firewall, driver's side, accessed from the engine bay.

I do not have pictures on the computer in the truck, but I can tell you exactly how to find it.


Go to truck, open hood, on the firewall, on the driver's side, locate the large round cannon plug, then look down and out just a bit. Hidden well behind a bunch of BS and wiring, near the inner fender, is a long, narrow plug with a 10mm bolt in the middle. That is the PCM plug.


Where is the truck located?

Back in Jersey. I always thought that was it. Is a PCM swap plug and play or will it require wiring?

EDIT: I had taken that connection apart before and there was nothing abnormal about it. The seal was good, no water, no debris, all 100%.