Toyota Repair: Toyota Electrical System EFI problem, toyota 4x4 pickup, blown fuse

Question
Hi Ted,

About two years ago I bought a 1989 Toyota 4X4 pickup, V-6.  Everything was basically in pretty good shape except that the power steering had a small leak in that "steering box"(?).  Well, that all worked fine for months, andthen one day while I was riding down the road, the engine just killed, and I mean just slap ass died like it had been pole axed.  It went from 55 to nothing....it didn;t miss of anything first, just DIED.  Afterward, NO fire whatsoever.

I popped the hood and looked all around, and that didn;t fix it (Ha!).  That just about exhausted my mechanical abilities, so I called a cousin to come pull me to the house with it.  While waiting for him to get to me, I piddled around looking at the fuses, etc.  

I got home and my father and I looked at it a bit.  He was am Installer for Western Electric/ AT&T/AT&T Technologies/Lucent, and is a sharp electrician in general.  Well, I went ahead and changed the distributor cap and rotor, plugs, plug wires, belts, etc. while I was in there fooling around, and Dadwas poking around with a multimeter.  He got over to the fuse panel (the one under the hood by the battery), and he said "Son, I thought that you checked the fuses.  Well, I was without my glasses, so I overlooked a blown fuse...fuse number 1, labeled "EFI".  I swapped the fuse, and it cranked right up, no problem, and then ran fine.

Obviously, what screwed up was still bad, but I thought that mayeb ut just blew and would be OK.  A few months afterward, I was riding on the interstate with a friend, and I smelled something like plastic burning.  I thought it was elsewhere, "in the air" if you will, and went on about my business because I was near my exit.

I pulled over at the exit and went on down, but when I stopped to turn, the trck started missing a bit. I turned and it died!

I got out and popped the hood, and then knew that it wa smy truck smelling.  It smelled JUST LIKE burning plastic, which it was.  The fuse was TOTALLY melted, and the fuse panel was, too.  The actual fuse clips melted OUT and lost contact, which was I THINK when it crapped out.  I hope that it didn't fry the processor.

The fuse was the proper current, and there was nothing metal that fell into the fuse panel to make it refuse to blow and break the circuit.  I had gotten the fuse from one of those big 18 wheeler tool sales, so that may have been it.  I hope that it simply lost power when the fuse "skeleton" fell though and broke the connection, and NOT that it burst something up.

I re-wired the melted part with an in-line flat fuse holder, and I tried it and it burnt again, and I looked at the wiring, noticing that a white/red stripe wire was melted coming out of a plug in the fuse panel, going into the passenger's side firewall by the battery.

I looked all over and taped any spots that looked like they were possibly rubbing,and tried again...no fire, no blown fuse, nothing.

Again, I am no mechanic, so I am lost here.  Right now, there's no fire at all, so something is holding that out, or tore up.  

The wire that melted is one that goes to a six wired plug on the fuse panel, red on white.

What would you suggest that I do to troubleshoot this? I would think that maybe this has something to with the fuel pump, but I am not sure.  If I have to get to it, would it be easier top pull the bed or the tank?

I realize that this is probably a simplfied question, but any and all if that you could direct my way, the better.  A "plan of attack" on this problem would be even better!!

I look forward to hearing from you at your convenience.

Thanks a bunch!!!

Bubba Phillips  

Answer
The white/red wire supplies 12volts to quite a few components including the efi main relay, the circuit opening(fuel pump) relay the fuel injectors, the O2 sensor, the air flow meter, the ECU and a few vacuum switching valves.
This wire is shorting to ground somewhere in the wire harness, the most likely place is at the O2 sensor, check the connections for any corrosion, cut the harness open if necessary to find the problem, the fuel pump is not the problem, you need to find where the w/r wire is shorting to ground.