OK, Sous' pics show it all, both the wires coming off of it to the alternator and one to the junction box. I'll try my test light to that little stud in the AM and see what it renders. I'm thinking/hoping that I knocked a connector block loose in the column area while I was in there. I do not have nor think I should have a set up like PACamper shows. Power in, power out to the starter, alt and junction box (that's what they seem to call that under the hood fuse box) and the little activation lead.

 

I am glad that is what you were looking for Mark, let us know what you find.

 

When I apply power to that little post on that relay the engine cranks over. I'm thinking that I disturbed a connector somewhere under the dash. I have no turn signals, 4 ways do work, wipers do work. It seems that everything is working except:

No WTS light
No crank
It did crank at first but no start, no smoke, just stopped cranking with no provocation on my part (honest)
No turn signals
No OBD connection

Is there a place/connection that handles all of these things?

Where does the ignition wiring come out that I can test it? (Seeing as everything else works as it should I think it's OK).

 

Looking at that schematic, is that digital transmission range sensor the white unit on the column, or is it down on the transmission?

 

It sounds like your starter solenoid is good and grounded properly, so it makes sense now that your trigger wire for that solenoid ("COM") is not getting hot. I've not had to trace that part yet

It sounds like you are checking the shifter position for the starter. Block the wheels and put the trans in Neutral. Usually it will start there, even if the Park position indicator or shifter is out of alignment.

Yeah, I know that is going around your problem a little bit, but it is also very simple to test.

Though I'd be concerned as to why you do not have an OBD connection ???

Maybe someone with more electrical troubleshooting can jump in here??

 

I am please, I mean thrilled, I mean really ecstatic to report progress. I pulled the dash back off and that gives me a good line of sight at the back of the GEM and the two wire blocks that mount to it. The one on the right was not properly seated. I removed it looked at it the best I could in there and carefully reinstalled it. When done it was flush with the one next to it and I got everything except crank now. I have WTS light, turn signals aaaaanddddddddd it started with a jump at the fender solenoid.

So now it's the starter relay wiring circuit that I need to troubleshoot. The two fuses associated with that circuit (I think it's 20 and 21) both have power to the left prong and the fuses ohm good. It looks like the piece I am looking for next is down on the tranny.

 

Good work Mark!

 

Whoo-hooo! Getting close! Go get it

 

What happened, so others will beware, the one block went in crooked and bound up. I tried cranking down on it but it made crackling noises so I stopped. Taking that thing out is a chore and I really didn't want to go through it again but it had to be done.

 

Was this the GEM?

 

Yes.

And my next step towards solving this problem...I have discovered that a small amount of power is coming through the small wire to the starter relay, the one that leads from the transmission position detector. When I work the shift selector through the positions that power cuts out when shifted out of park and neutral. In other words, the shift position sensor is working properly but power is leaking in when it shouldn't be and not being applied when it should be. I have looked all around this steering column and can't find the electrical part of the ignition switch, is it that large white block mounted to the bottom of the column with the wires connected to it?

 

I haven't pulled one out of these trucks yet, but that is what they look like in a gasser 460.

I grabbed a pic from the internet:



There is a long rod that moves that metal pin. The different positions are Off, Run, Start, Light Speed, and Time Travel.

Okay, I don't really remember the positions, but that is what the switch looked like in it. IIRC it was about $50 on the gasser.

 

OK, that's the box I'm talking about and the more I think about it the more it had to be it. I vaguely remember some sort of linkage that runs from the key cylinder to somewhere and down to that thing has to be it. That'll be my mission for tomorrow.

Thanks.

 

No problem. But be careful!

I don't know if that ignition switch bypasses the transmission interlock ("are you in Park or Neutral before I let it start"). I *think* it does, but I am not positive.

The common problem that seems to occur here is when one or both of the allen screws comes loose on the shifter inside the column and allows enough slop that the transmission-mounted gear position indicator doesn't get properly positioned into park.

Interestingly, it usually still works in Neutral, though. That's the reason I mentioned trying it in neutral with the wheels blocked (so it doesn't roll when not in park, LOL)- just in case the Park position wasn't right from the steering column or whatever.

Just eliminates one potential problem area while you narrow it all down

Does your PCM and OBD connector work now, too?

FYI. That Ignition switch unit is not serviceable. Just replace if you find it faulty. On the gasser I replaced it due to low voltage coming out of the ignition switch. Internal corrosion was what I figured. The new unit resolved that issue.

On that gasser, we were troubleshooting ignition and fuel pump in the EEC-IV system.

If you have a helper to turn the key, you can put your DVOM on 12v scale, negative lead on battery (-) and positive lead on that small COM wire on top of your solenoid and hold the key to crank for 3 seconds and read the +12v on your meter.

It should be very close to your battery voltage.

You've been testing things that sort-of check this up to now. This test will tell you EXACTLY what shortcoming or weakness you are facing on that wire, which might help narrow it down.

For example, if the voltage is about 10volts on that line, then test the incoming voltage on the power supply wire of the plug going into the ignition switch. If it is low...bad wire. If it is fine, replace the ignition switch.

That's an example, not a diagnosis yet

Don't lose heart. These kinds of issues are why you can get good deals on cantankerous trucks. If you can fix it, you WIN!

 

I get low voltage out of that COM wire all the time when the trans selector is in P or N, no other times. I am deriving three things from that:
1) Trans position detector is working.
2) That COM wire is good from trans to the relay.
3) Something is bleeding power to that line somewhere.
4) I forget whether turning the key cut the low power to that COM line or not, will check before proceeding further.

Thanks!