So I just swapped out the under dash harness and...

[captainspeky]

I swapped the under dash harness and fuse box out of a Aug '88 4WD LE automatic (it's a lost cause rust bucket) and put it into my driver Aug '87 2WD cargo panel 5 speed. My stereo wires and plugs were chopped and I was going to try to hook up the factory cruise control, fogs and power locks eventually. Got everything hooked up and start the engine and I get this terrible chatter coming form the the area of the distributor. Not sure what I may have overlooked. Maybe the EFI or power main relays are not in the right space? The relays were layed out a bit different and there was a "fuel pump" relay along with a few other relays I haven't been able to identify on a different harness in the 88.
I've started it a few times briefly. I'm not sure what is the cause of all of the chatter. I hope I didn't screw anything up?

[captainspeky]

Anyone care to point out where the clutch start relay is on MT vans?

[Burntboot]

It should be on the outboard side of the engine bay, forward of the air flow meter, just aft of where the wiring harness loops over the "frame", tucked in pretty good and hard to see

[captainspeky]

It should be on the outboard side of the engine bay, forward of the air flow meter, just aft of where the wiring harness loops over the "frame", tucked in pretty good and hard to see

Thanks, Burnboot. I had to get a refresher on my nautical terminology for those instructions. The only difference I could find in the diagram was the manual start relay and the AT neutral safety switch, I don't think the MSR was the culprit because there was no difference going from the ignition switch into the chassis wires.

But, For whatever reason, and after staring at wiring 3 different dash harnesses and diagrams for a week completely stumped, I plug the LE harness in again today and BINGO it runs fine. I'm guessing I forgot to plug something in?
Seems my 2wd 5 speed harness doesn't have a power main relay? I pulled the one on the LE and it cranked. Plugged it back in and it still cranked. It's must be a Krampus miracle... 👹

[Burntboot]

You are kinda in uncharted territory here.
Not aware of anyone doing specifically the same thing.

I know when I swapped from my(std trans) DX cluster to an (auto trans) LE pack there were several wires I had to swap positions within plugs.
It is possible that while the plugs look correct, the orientation of the wires within is not??

Another possible wild card is that 88-89 had different engine management systems from 86-87, no idea how that would affect dash harnesses, if at all, just another thing to be aware of.

[captainspeky]

Burnboot,
Yea, I couldn't find anything about people doing this before. I assumed someone might have upgraded their harness either because of the options (everyone wants factory fog lights it seems), or maybe because of old burnt wires and melted plugs. The manuals I have are rather vague and wiring diagrams only really conceptualize what they do without identifying much visually. I suppose I could have just spliced the different parts of the harnesses together, but when I went through all of the pins/plugs between the 3 harnesses and they were the same for the most part on the important stuff like ignition, etc with the exception of the missing power main relay (?) on the MT and an extra triode on the LE behind the stereo(?). My instrument cluster now reads that the overdrive is engaged, LOL so like you said with engine management systems, I hope it's not sending the ECU any weird information.

Still not out of the water yet. Going for a test drive around town today to see how it goes. I don't post much, but I might do a comprehensive thread about this with pictures of the plugs, what they do, what the individual pins do and how the harnesses differ from years, trims and transmissions.