Recently bought a beautiful 1990 Mitsu Mighty Max, shop said the ECU was bad but a visual inspection of the ECU board didn't show any scarring or anything concerning (def no popped caps). I went out to the truck with the ECU and plug it in and the truck cranks very well. I tested spark and I noticed I wasn't getting spark through the wires. So I replace the wires and plugs but still no success. Fuel gets to the cylinder as well as spark but I still dont have any kind of firing. Engine has low miles and its in pretty good shape but this issue is what parked it a couple years ago and it's been sitting in a yard since.
The mechanic thought it was the ECU but I don't trust his opinion as he isn't a very successful mechanic. That being said after this most recent event I am suspect of the ECU again. Anyone whos had a ECU fail on these trucks, have you guys seen a similar issue? Crank but no fire? Everything appears to work and i've been slowing going through the ignition system and testing with a multimeter, it looks like most of the electronics are functioning. The only issue I found was a burnt out wiper blade so far. When I turn the key I get a click from the ECU (or that other control box down there) and it really wants to fire but something is just missing. Ive also check most of the fuses, the ones on the battery lead and in the cab for sure.
I don't hear a fuel pump hum when the key is in the ignition, is the fuel pump a noticeable noise or pretty quiet?
One thing to note, when the key is in the ignition the buzzer is blaring a constant buzz. I was wondering if this was because something was wrong in the electrical system, but google didn't help me out there. I disconnected it because it was unbearable to listen to but it was any time when the key was in the ignition.
I want this thing to run so bad! It freaking mint!
Thanks guy! Love the forum and Love these trucks!