Hi guys,

Not sure where to go with this one. Did a complete swap from an 84 chassis to a 90 chassis due to rust out issues. Migrated everything over. Dash, wiring, everything. Now, as I'm testing things, I find that I have a no crank issue. My first thought was the neutral safety switch - Eureka! It wasn't hooked up. Plugged that bad boy in and... nothing. Probing the wires in the harness, the only one that has power is the thin blue wire. Neither Yellow nor Purple (I can't remember which one was upstream\downstream) had any juice when I turn the key to the Start position.

Fishing some wires out from under the dash, I found a set of yellow and purple that were not hooked to anything. Probed there, but there's no juice there while attempting to crank either. After some reading I found that it was probably for a clutch safety switch (as they wired for both in some models), so I disregarded.

I have other interior power. Dome light. Gauges. When I attempt to crank, the temp gauge pegs out while the key is in the start position, but then settles back to zip when not cranking. I doubt that's a clue, though. When I checked the fuses, I am missing a couple but there is no Crank fuse. There's no receptacle there, even though its labeled.

I'm stumped. I don't know enough about the electrical on these cars to troubleshoot the issue further. Does anyone have any ideas?

Thanks in advance,
Mike

 

I really feel like this is a wire harness somewhere that's not plugged in all the way or something silly like that. Everything worked fine before it got swapped so I'd be surprised if the ignition switch just up and died. Or maybe it's because I don't have a wire hooked up under the hood somewhere?

I have two thicker red wires with fusible links connected to the same terminal as the battery. The purple wire is connected to the S terminal on the mini starter. I didn't think they went anywhere else other than back to the C100 block.

 

Yes , What you need to do is to start at the ignition switch , using a voltmeter when the key is turned to start see if the yellow wire gets +12 volts . If yes , next go to the starter interrupt relay and so on till the +12 with the key in the start position disappears . If this is a swap , what harness did you use , the 1990 or the 1984 ? (1984 won't have the starter relay cause VATS wasn't till 1989) This diagram is pretty much the same way they all were wired in that it's a yellow wire coming from the switch that eventually becomes a purple wire going to the starter , after it been through a least a neutral safety switch (auto trans) or a clutch switch (manual) and if the wiring is 1989 or later the starter interrupt relay .

Oh , and if the yellow wire does not get +12 volts when the key is turned to start you either do have a bad switch (doubtful as you say it worked before the swap) or you don't have something feeding the switch connected correctly (like the fusable links that connect to the big terminal on the starter) .

 

All wiring is from the 84. The only thing that came from the 90 aside from the shell is the HVAC stuff.

Alrighty, then. I'll drop the steering column and check there I guess. What is upstream of the ignition switch if there's no power there?

 

The only thing upstream of the ignition switch is the fusable link shown in this 1984 diagram . if you have no power to the yellow when trying to crank and your sure your wires are all hooked up at the starter the fusable link would be the most likely suspect . They can go open circuit without showing outward signs , and since the harness was moved from one car to the next it's possible the link did break somewhere unseen due to being disturbed from it's original state .

 

I replaced both fusible links at the starter with 14 gauge fusible links, so hopefully they weren't junk.

 

Alright. So, on the ignition switch, I have two harnesses; one blue and one black that interlock. Each harness has a thick red wire that have 12v. The yellow wire, in the blue harness, has no power with the ignition in any position as far as I can tell. So being that I have power at red, it should be safe to assume that this issue is the ignition switch, right?

 

As long as there are no other than the two big red wires , and both of them do have +12 v on them , and you get nothing on the yellow in the start position , your two options are a bad switch or a switch that isn't being pushed fully all the way to where the switch's contacts make .

 

Ignition switch was the culprit!

Swapped it out and now the start engages.

Thanks again!

 

That's Great !

I am happy to help , especially since you did 99% of it yourself , all I did was give you the "second opinion" as it were ...