Tony Sestito
Tony Sestito PowerDork
5/4/21 4:31 p.m.

I posted this mess over on my Power Wagon Build Thread, but I'm posting it for the larger audience here because I'm stumped.

Last weekend, I went to start the truck, and CLACKCKCKCKCK. Not enough juice to turn it over, even with a charged battery. Then I see this:

Uhh... YIKES.

The harness that went to the old EGR Timer (that's been gone for years), the choke thermostat temperature range switch, the oil pressure switch, and other nonfunctioning emissions stuff decided to fry itself. Working theory is that the choke thermostat failed and sent all its current back through the power wire, causing a meltfest. That power wire is also part of the Ignition circuit; it preheats the choke thermostat when the key is on. 

I pulled that entire harness out. It's mostly trash.

With it disconnected, the truck won't crank. The connector where power came from is still intact (the red wire with the barrel connector):

That wire gets 12v when the key is on.

I'm assuming that I need to complete the circuit somehow. This truck is equipped with a starter relay:

And here are some wiring diagrams. This is the main engine harness:

Here's the harness that got fried that I pulled out:

Here's the choke system and some notes, including that it's part of the ignition system:

The goal is to get it running again, but without that harness if possible. Choke control can be bypassed (it doesn't like choke anyway, and for "other reasons" I can't talk about yet) and I don't need anything that has to do with the EGR system. I would, however, like to get the oil pressure switch wired back up. 

So, Hive Mind, how should I fix this? Keep in mind that there are zero off-the-shelf wiring harness solutions available for the truck. And besides, it seems to be a matter of running a few new wires, not an entire harness. Thanks in advance!

Tony Sestito
Tony Sestito PowerDork
5/4/21 5:06 p.m.

Ok, so after all of that... the truck just started and ran. Without that harness. That's not supposed to be possible. 

So yeah, any insight into ANY of this... fire away. laugh

drock25too Reader
5/4/21 5:16 p.m.

This is how I have wired race cars for years.  And the book it came from. 

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