4.0 Swap Engines, Computer Fire

[93RedRanger]

So here's the deal. I've got a 1993 4x4 4.0L with a manual transmission. About six months ago I started having some trouble with it. Several things went wrong with it, but the most prominent was a leaking water pump that caused severe overheating. I replaced the water pump, thermostat, radiator, and radiator hoses to the tune of about $400. Then I needed new ball joints. Another $400. Those items and some more misc. maintenance had me up over $1,200 in repairs. Two weeks later I start noticing white smoke coming out of the tail pipe. A head job was going to be over $600, so I said to myself that I would just get a used engine and replace the motor. Found an engine with about 75,000 miles on it ($700 plus a $400 for new gaskets, flywheel, clutch kit and other parts and a few new tools) to replace mine that had 190,000 or so on it. Good deal right?

Well two days into tearing down the old engine I get a hernia and have to have surgery. Can't work on the truck for months. Finally get healed up and get up the motivation to get started again. Worked most of the weekend and took one day off work to finish prepping the other engine and get it installed. Fire it up the first time... runs great! Singing along like a song.

That was last night. I ran it for about twenty minutes in the garage to make sure that everything was good and then went to bed exhausted. Months of waiting and $2,300 in repairs, but now I've got a reliable running truck, right? Well tonight I get home from work and button up a few last things and take her out for a spin around the neighborhood. Everything is running great for about ten minutes and then it suddenly goes dead and the cab fills with smoke. I get my buddy that lives down the road to tow me back home and investigate. All this work and time and the computer has caught on fire! Pulled out the computer and it seems the pin that caught on fire is connected to a tan/yellow wire that runs to the ignition module. It got so hot that it melted the circuit board in a couple places. I couldn't breath very well for hours.

Anyway, I know this is long winded, but I just thought I'd tell the whole depressing story. Not sure what to do now. I've got $2300 in a truck that doesn't run with all kinds of new parts on it. I'm tired of sinking money in this thing. Any suggestions? I was having some lighting problems before, but I thought it was due to how my brake light circuit was used to tie into a light in my camper top, but maybe it was the computer all along. It's hard to believe that I hooked something up wrong that caused the computer to catch on fire since it ran fine for 30 minutes before that. It was running perfect up until the point that it died. No warning or anything, just died and then filled the cab with smoke. I'd like to think that the computer is just bad, but I hate to put money in another one and try it just to see a new one burned up by whatever caused this to happen. Anyone ever seen this kind of thing before? What should I do here?

 

[BlackBII]

I'm going to guess that something wasn't hooked up right and or wasn't grounded, causing an overload on that wire and then the fire.

But.....I'm curious as to how you thought "smoke from the tailpipe" was cause for a whole new motor??

What color was the smoke? Or was it steam?

 

[93RedRanger]

Took it to a trusted mechanic and he diagnosed it as a head gasket problem. White "smoke", "steam". All the same it was white, not blue or black. Don't think I hooked anything up wrong, though I haven't had time to retrace my steps yet.

 

[trail B2]

Ive had things like that happen to me it makes you really feel beat up.I understand why you changed the whole motor because of the other money you just put to be able to drive it out.What to do now really depends on how much you can get a ECU for.My next step would be to go to the U Pull and see what you can get a computer for clean all connections plus grounds and see if your willing to take a chance.

 

[mud390]

I say throw a new ECU in it, clean up the wiring and terminals that were damaged and see what it does.

Kris

 

[93RedRanger]

Yeah, I've been thinking about it all day and I'm considering just going ahead and trying to find a computer at a junk yard and throw it in and see what happens. I don't know what else to do at this point. I hate to give up on the truck if that's all that it needs. I can't find anything wrong in the circuit that burned up. It just doesn't make sense. I just hope the next one doesn't burn up.

 

[93RedRanger]

Now the problem I'm running into is that noone has this computer anymore. I even called the Ford place out of desperation and they can't even get them anymore. They said that they don't make them anymore. I called every parts store and junk yard in the book. NOTHING. I even called other states as far away as California (I live in AL). How depressing. I had one of the salvage guys look it up in his computer network and he said there were only 3 in the entire country that he could see. I called two of them and no cigar. The other guy said he didn't know if he had it or not and hasn't called me back. I'm not hopeful. Any suggestions out there on were to find this computer? The number on it is F37F-UC. If anyone know where to locate one or knows where one is I would greatly appreciate the help!

 

[93RedRanger]

After looking at another thread (http://www.therangerstation.com/forums/showthread.php?t=195) I think that someone put a junk yard computer from a 93 Explorer in here. According to Natedog's numbers I need a F37F-LA computer. Eureka! Maybe this one won't be as hard to find. By the way, does anyone know where the ignition module is on these trucks?

 

[snoopdoggie]

Not sure on the Ranger but on an Explorer it is on the radiator core support. Between the battery(pass side) and the radiator.

 

[93RedRanger]

Called the first junk yard on the list from the other day again, and now they magically found a computer! Awesome. Got a new ignition coil from Autozone. Double awesome. Now I'm scared to death to throw them in there without really knowing what happened the first time to burn up the computer. I've looked over the whole wiring harness and can't find anything wrong that I hooked up. I was reading on here in some other posts that Ford's TFI module's that they used for these year model trucks are notorious for going bad with no warning. My current theory is that the ignition module screwed up and caused too much current to be pulled the circuit in the computer causing it to melt down. That's all I can really figure at the moment. Has anyone ever experienced anything like this before or heard of anything like this? Is there anything else (specifically, not just "check grounds") that I should check before I take a chance on roasting new parts? Other than the computer there are no signs of damage anywhere else under the hood.

 

[toecutter]

Does a 4.0L use a TFI module? I thought those were for vehicles that don't have coil packs. Every 4.0L I have seen has coil packs on it. The ignition control module mounts to the firewall in front of the battery on the drivers side, the explorers have the same setup but on the passengers side.

 

[93RedRanger]

Well I found where the ICM is on the radiator support, but I don't think that was the problem after all. I was doing some double checking before I reinstalled the new computer and it seems that I had the connector upside down when trying to trace the wire that caused the problem. The pin in the computer that caught on fire is actually on a dark green wire in the connector that goes to something called the "PCM shorting bar" according to the wiring diagram. On another thread I saw this called the Octane Adjust shorting bar. Does anyone know the function of the PCM shorting bar and where I might find it? Does anyone have a clue what in that circuit could cause a computer to draw to much current and catch on fire? Is there something I could have hooked up wrong that I should look for or is it just a component failure at an inopportune time?

 

[93RedRanger]

Got it!!!! Thank God for wiring diagrams! Turns out that when I jacked the transmission up a little bit to better line up the input shaft through the flywheel I accidentally mashed the drivers side O2 sensor between the transmission bell housing and the cab. A sharp area on the underside of the cab caused a break in the wiring insulation and a short. Never knew that a shorted out O2 sensor wire could cause your PCM to catch on fire. Good thing I didn't just throw the new computer in and try it thinking that the computer had gone bad. I would have fried that one too. Anyway, thanks to all you guys for the help.

 

[JoeCanada]

Hope it all works out for you...I bought my '94 about 3 years ago and have been fixing it ever since...blown water pump, cracked heads, new motor, new brakes all around, new bearings...and on and on... sucks to fix one more thing, then just when you think you've got it done, another thing goes wrong.

Just keep looking forward to that day when you won't have to fix anything else...at least for a couple months...

 

[93RedRanger]

I know what you mean. I drove it to work today for the first time in months. It just served to remind me of all the other crap that I still need to fix on it. I'm going to have to have brakes all around pretty soon and the used engine I put in has a pretty good tick in the valve train. I'm hoping that it will clear up after I run it a little while and blow the gunk out of it from sitting. Also, I've got to fix that awful popping coming from the drive shaft when I start out. Had to go to the part store and get a flasher when I got to work because my blinkers weren't working. It's like it never ends. Oh, and it vibrates pretty good going down the road like one of the tires is out of balance. Also pulls to the right and needs an alignment. BUT... it's going up the road now and that's something it wouldn't do last week! Anyhow, thanks for all the encouragement and help.