Fuel pump running w/ KOEO

Summary: Purchased a 97 tacoma 3.4l 4x4 recently with a no start condition, I've fixed many cars and rebuilt many engines so I figured it wouldn't be too bad if I get it for the right price, I was wrong! This things been a pain in the butt!

I've tested fuel pressure, reads 44psi before rail. Strong spark, timings right on the money, compression checks out fine. Haven't checked for injector pulse because some idiot decided he needed my noid light tester more than I did and stole it. However, I tried squirting a bit of gas into the TB and it fired right up and ran for 8 seconds or so, even ran it for 20seconds with starter fluid. Ran perfect, no knocks, ticks, backfire, etc.... I also pulled the manifold off and cleaned/flushed the injectors and put new seals on them but still no improvement.

What I did notice was that with key on and engine off, the fuel pump runs constantly instead of the regular prime and stop it should be doing. Relays were good, fuses were good so I decided to pull the ECM and found some burnt traces, capacitors and a resistor. Ordered one online and waiting for it to come in to test it.
My question is, what might've caused the failure? Alternator tested good at a consistent 13.6v-13.8v, no burnt wires, new fuel pump, grounds look sound and checked out with fluke meter as good. Any suggestions would be helpful! Thanks!

 

Any signs around the ignition switch of hot wiring or old alarm system.? Possible inverted polarity jump start attempt?

 

No signs of tampering with ignition or switch, no alarm on it. Maybe you're right about the crossed polarity jump, seems like a possible candidate. I also noticed the ground from the battery to fender well wasn't there anymore, another possible cause maybe?

 

The ground to the fender is the primary ground wire for the body electrical system. That may be an issue there. There is SUPPOSED to also be a ground strap from the cylinder head (on the passenger's side, near the back) to the firewall.

As for the running issue, yeah, I would think you have a bad ECU refusing to fire the injectors, and possibly engaging the fuel pump relay all the time. Burnt terminals and blown capacitors are a concern. I would check all of the ground wires for the ECU, as well as check the resistance of each of the injectors, to be sure one did not short out.

 

The ground wire from head to firewall seems kinda dodgy, PO extended it with a butt connector and 2 wires side by side to make it bigger. . I'll be replacing that wire with a solid one and some copper lug terminals as well as the one to the fender well. 4 injectors turned up 13.8ohms and 2 were 13.7ohms so they all seem good.

Any idea of where the ECU grounds to? Is it grounded by its body or a wire ground? I'll be sure to check that though as I really don't want to go through the BS looking for another box and waiting for shipping again.