Crawdad

The magic smoke came out of my 4runner's ECU today - I was in the woods, and the A/T Oil Temp, Battery, and Brake lights all came on. Battery gauge was about halfway. It died, and wouldn't crank, so I had a buddy jump it. It jumped fine, and ran for about a minute before the dash lights came back on. I tried to get it turned around and back out of the woods, but the idle started going funky (up and down up and down) and it died.

This time when it died, none of the interior lights would come on, and it wouldn't do anything when you tried to crank it. We pulled the underhood fuse panel, and noticed that the alternator fuse was blown, as was the EFI fuse. We jumped these two fuses with wire, and it would turn over, but not crank, and then the ECU let out a wonderful puff of smoke.

I'm sure I fried my ecu, so I just bought one from ebay. ANy other ideas?

CJM

Sounds like your alt took a dump and by jumping those fuses you fried the stuff well.

abecedarian

x2
either the regulator went, or the diodes

Crawdad

Yeah, by the time the well-meaning guys I was with pulled out wire and started jumping fuses, it was too late for me to stop them.

Oh well. I just replaced all the fuses but the alt fuse, and everything works. The engine will crank and crank and crank but won't turn over - sound like the ECU?

How can I test to find out if it is the alternator, the diodes, or the voltage regulator? Or do I need to wait until I replace the ECU?

abecedarian

the only safe way to test the alternator would be to take it down to a shop and have it bench tested.
if you know someone with a compatible ECU, you could try swapping them.

CJM

Listen for the fuel pump to come on and see if you hear it. Hear it its not that, dont hear it the trucks not getting fuel due to the EFI fuse.

I would also check the AFM sensor and see if thats shot, will cause the same issue. Also try and swap ECUs with someone..

Crawdad

I'll check the fuel pump, the EFI fuse isn't blowing anymore, I replaced all the fuses but the 80A alternator fuse, and went ahead and jumped the alt fuse with an inline 50A fuse (That didn't blow). With the alt fuse jumped, the truck cranks, all the interior stuff works, it just won't fire. The smoke came directly from the ECU, so I'm pretty sure it's dead. Where is the AFM sensor located?

My father in law has a 1990 4runner but his (and his ECU) are 5spd and won't hook up from what he says.

I found and bought as 1990 3VZE A/T ECU from ebay for around $100. None of the local junkyards had anything.

Here's what I think happened: the alternator died, popped the Alternator fuse under the hood, which killed power to the interior of the car. While trying to jump blown fuses to get it to start, my well-meaning buddies accidently jumped 12v from the ALT to the EFI fuse under the hood, making the magic smoke leak out of the ECU. I should be mad, but there ain't nothing I can do about it, I reckon.

Where can I get that special 80A fuse that goes in the alternator slot under the hood?

CJM

The AFM is an air flow meter iirc and is mounted right at the airbox, it measures airflow. If it dont work the truck wont run.