i don't think it should have a asd relay. have you checked the ground connections? maybe the coil is overheating.

 

It's not the coil, I have 3 spares (all verified good) and swapping it makes no difference. Also have spare ECU and voltage regulator, and swapping those in doesn't help either. It's got to be a wire or connection somewhere, but for the life of me I can't figure out where. When I've traced wires, they've checked good. Connections have all been cleaned and double checked over and over, plug-in connectors as well. I've torn the wiring harness out and gone down each wire (yes, even those that wouldn't matter) and they're all good.

I'm going to re-wire the ignition system according to the info SEAL posted and see if that makes a difference. Should know soon, since the problem is so frequent I shouldn't have to wait long for it to happen again. If it goes more than a day or two, that'll mean something I did, or touched, or brushed up against, made a difference, so at least, maybe, I'll have a place to start.

Thanks again.

 

the ones SEAL posted looks the same as the one you did but just drawn different. you should check the resistance between pin#5 on the ecu and the negative post of the battery or a known good ground connection. should be no resistance.

 

I think I found the problem, after all this time. It started fine, again, and I was about to shut it down and start going over the wiring and I decided once again to play with connections. Started with the battery, then starter relay, then voltage regulator, then ECU...when I pushed down on the ECU, it started to stall. I let go, and it idled smooth again. Did this about half a dozen times, until finally I pushed it in tight enough that the engine died. Sure enough, it wouldn't fire back up until I raised the connector slightly. Once it's plugged in tight and the screw is tightened, it kills it.

Really, I don't know whether to laugh or cry. Been annoyed by this for the last few years. Makes all the sense in the world now, though. I'm a stickler for making sure connections are snug, so when I was swapping out the ECU to test it, I was making the same bad connection again. It wasn't until the connector was able to work itself up off the ECU a teensy bit that it would fire again, but would eventually lose the connection until it was bumped, or it was in the mood, whatever.

If it doesn't start tomorrow, I think I'm going to tear out everything electronic and put an old points distributor in it. Pretty sure I can make that one work no matter what.

Thanks, guys, for the help.

 

crazzywolfie; In his diagram where is the wire that provides a full 12 volts to the coil for start up? That is the difference.

brhodes; Bad connections are 95% of the electrical problems I have seen on these trucks. Old age is hell but I am glad you found the problem.

 

i seen that but i don't think that wire is that important. i was not able to find a way to hook that wire up to my power distribution center and i would say my truck starts about the same if not better without it.

 

Me too. I'm sick of seeing my favorite vehicle sit around the yard because I can't find the problem with it. Also a bit embarrassing, not being able to figure out the problem with my own truck, honestly.

As for old age being hell...Not sure which of us you're talking about (me, or my truck), but yep, lots of miles on both, for sure.

 

I was referring to the truck but I guess it fits me to. LOL

A full 12 volts at the coil means you get a hotter spark, when it needs it, when starting. This is especially needed when it is cold. Engineers build in a lot of things that may not always be needed but they have to take all conditions into account.