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Logic says that his is an electrical thermal fault, triggered by a hot soak. Logic is useful, as it is the best way of going wrong with confidence...

You find this kind of fault with something to cool components one at a time. I used to use r12 for this, before it went to $20/lb. r134 will work, too. Tap a can with a valved hose and run the truck up to operating temp, shut it down, and wait until it won't crank, then cool suspected components/connectors until it cranks and do this one at a time until you find it, attempting cranking each time.

I'd try the coil and power transistor and connectors, the doodads in the distributor, the tach connector, the electronic gizmos on the bottom of the coil bracket, and the engine harness connectors at the firewall. ECU last.

I assume you checked the ecu boards for evidence of capacitor leakage and board trace damage?


Yes, opened up my ecu last night and couldn't see anything wrong, but from reading more it may not look like anything is wrong to be bad. I just ordered a rebuilt one with lifetime warranty. In a few days maybe I'll know something.
Does anyone want my extra ecu? It's from a '90 Montero V6 5 speed and won't work in mine. I paid $300, I'd sell for $200 shipped, I guarantee it to be good, or your money back.

1989 SWB V6 5 speed 230K