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Need some help 98 6.5 electrical-need to hardwire my truck

Russell said:
Ignition switches can and do go bad in this body style, but its due to mechanical wear and not shorting out. I just changed one in my 97 Tahoe because it would turn off while the truck was running, but it lost everything, not just the engine. If your switch is bad, the engine will not turn over in the start position.If your engine won't turn over and the truck is entirely dead (including the interior lights), also try tightening up your battery terminals. The side posts are famous for having a crappy connection that can arc open when you hit the starter.

That said, I am sure you need to replace your PMD. It's the cause of your problems. Even relocated they can still fail. The fact that your truck starts again after you change the ignition switch is by happen chance. As they cool down, then the PMD will come back to life. I am willing to be you'll wind up hacking up your harness for no good reason and it'll die again on you shortly afterwards. I know the PMD is bloody expensive, but I am sure enough this is your issue that I'll pay for it if you put it in and the problem persists.

Replace it with a grey model PMD. They are better than the black ones with improved drivers and self cooling capacity.

http://www.hdiesel.com/P/NewStanadynePMD/827
Click to expand...

Ok...what can the PMD do that will cause the switch to fail for all circuits feeding off of the ignition switch (not just "run")? If it's a cooldown issue, why would he not be able to walk out and start it now (after several days)?

I've had most of these thoughts, too, but I don't understand why power is failing for the rest of the ignition circuit. :dunno:
 
campfire said:
Ok...what can the PMD do that will cause the switch to fail for all circuits feeding off of the ignition switch (not just "run")? If it's a cooldown issue, why would he not be able to walk out and start it now (after several days)?

I've had most of these thoughts, too, but I don't understand why power is failing for the rest of the ignition circuit. :dunno:
Click to expand...

When I read the thread, I never saw him say that he was losing other ignition circuits? Just that the engine was dying on him and occasionally skipping a beat. That's what a PMD does when it dies. Or it puts the engine to full throttle and belch out black smoke before it dies and doesn't want to re-start for a couple minutes. That's what Penny used to do when her PMD was going bad haha! Made for lots of fun, the brakes could barely hold the truck back when it did that. Usually waited until I was stopped at a cross walk and some little old granny was walking in front of my truck with her little walker. Bad Penny!
 
Russell said:
When I read the thread, I never saw him say that he was losing other ignition circuits? Just that the engine was dying on him and occasionally skipping a beat. That's what a PMD does when it dies. Or it puts the engine to full throttle and belch out black smoke before it dies and doesn't want to re-start for a couple minutes. That's what Penny used to do when her PMD was going bad haha! Made for lots of fun, the brakes could barely hold the truck back when it did that. Usually waited until I was stopped at a cross walk and some little old granny was walking in front of my truck with her little walker. Bad Penny!
Click to expand...

:haha: :doah:

Basic summary (based on this thread and numerous text messages):

On 3 occasions this truck has been driving along and stalled for a second (like a failing PMD) before resuming normal driving. Then, upon shutting the engine off, he is able to turn to the "run" position normally, but when he goes to start it all the circuits getting power from the ignition die. Power is not restored until the switch is replaced. After the switch is replaced, the truck runs for a few days before repeating the cycle.

It sounds like a failing PMD is ruining the ignition switch, but it doesn't actually break until he hits the crank position *after* this weird gasping thing.

Is it possible/probable for a failing PMD (or anything else) to systematically wreck ignition switches? It's starting to sound like a predictable pattern... :dunno:
 
Russell said:
Ignition switches can and do go bad in this body style, but its due to mechanical wear and not shorting out. I just changed one in my 97 Tahoe because it would turn off while the truck was running, but it lost everything, not just the engine. If your switch is bad, the engine will not turn over in the start position.If your engine won't turn over and the truck is entirely dead (including the interior lights), also try tightening up your battery terminals. The side posts are famous for having a crappy connection that can arc open when you hit the starter.

That said, I am sure you need to replace your PMD. It's the cause of your problems. Even relocated they can still fail. The fact that your truck starts again after you change the ignition switch is by happen chance. As they cool down, then the PMD will come back to life. I am willing to be you'll wind up hacking up your harness for no good reason and it'll die again on you shortly afterwards. I know the PMD is bloody expensive, but I am sure enough this is your issue that I'll pay for it if you put it in and the problem persists.

Replace it with a grey model PMD. They are better than the black ones with improved drivers and self cooling capacity.

http://www.hdiesel.com/P/NewStanadynePMD/827
Click to expand...
Ethan and I had talked about the PMD and I wasn't willing to commit to it until I could see something connecting it to the ignition switch. I'm heading to get another ignition switch warrantied now. But now that I have someone to confirm the pmd is the problem I'll replace that too. Thanks @Russell and thanks @campfire
 
So on my lunch break I went and got the ignition harness warrantied at autozone. Went home, checked the battery terminals (tight) and tried turning the key. Silent like the grave. No crank. No dash light. Nothing that gets powered from the key worked. Went and unplugged my pmd and plugged it back in.
And key worked fine, and she started right up.
Technically the glow plug controller kept being wonky so they didn't get warm. Shut it off and tried again and they warmed up peachy. So I think this whole time it was a PmD problem just like Russell said.
I'm gonna grab a new one local for now to get me back reliable for work. And we will go from there.
 
That does sound like an ignition switch problem to me then. Being totally dead is unusual and wouldn't be caused by the PMD itself. That would be the stumbling / dying and not re-starting bit. Did you disturb anything else when you disconnected and reconnected the PMD? I am wondering if you've got a bad connection from the battery up to the junction block which feeds the ignition switch that is being disturbed when you are messing with the PMD and starts working again.
 
No. My pmd is mounted on the inner fender well by the driver battery. I literally popped the connector, blew on it and plugged t back in. Without touching anything.
 
Russell said:
That does sound like an ignition switch problem to me then. Being totally dead is unusual and wouldn't be caused by the PMD itself. That would be the stumbling / dying and not re-starting bit. Did you disturb anything else when you disconnected and reconnected the PMD? I am wondering if you've got a bad connection from the battery up to the junction block which feeds the ignition switch that is being disturbed when you are messing with the PMD and starts working again.
Click to expand...

I agree. The PMD doesn't have the ability to cut power to the ignition switch. It may very well be flaking out, but losing power intermittantly and regaining it after messing with the harness does sound like a loose connection. You shouldn't have been able to make ignition power appear or disappear by connecting or disconnecting the PMD plug. Dash lights & starter motor are not controlled by the PMD. It's just fuel supply. Something else is making them stay dark. If it's not repeatedly failing switches, it sounds like the feed wire is repeatedly conking out.
 
Smokinthehippies said:
Definitely appreciate that as the Internet provided bupkis while we were working on it this weekend.
Click to expand...

This. Trying to track down schematics was driving me up the wall. I still haven't seen anything that describes the pinout of the 17 wires in his ignition switch plug.

17 wires is far, far too many to have going to a 4-position switch.
 
Smokinthehippies said:
No. My pmd is mounted on the inner fender well by the driver battery. I literally popped the connector, blew on it and plugged t back in. Without touching anything.
Click to expand...

But simply jostling the connector probably bumped/tugged on other wires nearby. If nothing else, you would have tugged on the line that runs from the ignition switch to the PMD connector itself.
 
Well I said **** it and replaced the pmd with a #9 resistor. Keeping the old on as a backup. I also replaced the side post battery connectors with bolts and jam nuts on the driver and top post connectors on the passenger (no room with the turbo/intake).

Either way, it was the fastest cleanest startup since I've owned it. Also idled cleaner than it has before so maybe it was bad battery connections. I also hit it with some dielectric grease to keep them clean in the future. I'm gonna drive t to pick my wife up tonight since I had her Tahoe all day and I'll keep you guys posted.
 
Smokinthehippies said:
Well I said **** it and replaced the pmd with a #9 resistor. Keeping the old on as a backup. I also replaced the side post battery connectors with bolts and jam nuts on the driver and top post connectors on the passenger (no room with the turbo/intake).

Either way, it was the fastest cleanest startup since I've owned it. Also idled cleaner than it has before so maybe it was bad battery connections. I also hit it with some dielectric grease to keep them clean in the future. I'm gonna drive t to pick my wife up tonight since I had her Tahoe all day and I'll keep you guys posted.
Click to expand...

Cool. :popcorn:

FWIW, my dad's '93 6.5 rig has the same issue with side posts on the passenger side, but he has a bolt/nut combination squeezed in there anyway. It's a bit of a pain to service. Some day I predict that intake piece gets chucked in the trash. :rolleyes:
 
Yup I've done it on all of my 90s Chevys so far. I might find a way to change it over. One of my summer projects was to change that intake tube for something that deletes the resonator chamber anyway. But that's for next year. I'd be happy with a few good months of reliable service for the meantime.
 
I can certainly get you a pin out diagram of that connector at the base of the steering column if need be.
 
Cili said:
I can certainly get you a pin out diagram of that connector at the base of the steering column if need be.
Click to expand...
If you would when you get a chance I'd be super grateful. I'm hoping its licked now, but it wouldn't hurt to study it just for reference.
 
What's really dumb the more I think about it, is I bet the battery side terminals were the problem. Cuz the same day I installed the radio, I took the drivers battery out to replace the windshield washer resevoir and pump. And everytime Ive "fixed" it since, I've had to disconnect the batteries to do the work. Which magically made it better... I don't know that that's the case but I'll drive it for a bit and see how it shakes out.
 
Smokinthehippies said:
What's really dumb the more I think about it, is I bet the battery side terminals were the problem. Cuz the same day I installed the radio, I took the drivers battery out to replace the windshield washer resevoir and pump. And everytime Ive "fixed" it since, I've had to disconnect the batteries to do the work. Which magically made it better... I don't know that that's the case but I'll drive it for a bit and see how it shakes out.
Click to expand...


Ah...That is something that I didn't realize. That does look likely. We'll see how it goes.
 
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