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Is it the PMD or the ECM/PCM?

Harqobispal

Harqobispal

LIVE FREE or DIE HARD
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Hi All,

First of all i would like to say thank you to all on this site that have helped me and replied to me.

I bought my 1996 ext cab 4x4 6.5l TD about 1.5 years ago. Almost right away it started stalling when driving it. I did research and thought it was the PMD. I went online a bought the HEATH remote mount PMD kit that goes on the skid plate. I installed it and the truck ran great for about 1 year.

In the last 2 months is started stalling again. At any speed (usually in traffic in the middle lane at 10 mph) it will stall. When it does, i have noticed when you cycle the ignition, you get not glow plugs(WTS) light, no service throttle soon light, and no lift pump. The wierd thing is , if you wait usually 30 secs to 5 mins, all of the sudden these above mentioned devices reactivate, when you cycle the key. Then if you turn it all the way to start, the truck starts immediately. If those lights and devices do not come on , the truck will absolutely will not start.

I have already cleaned and checked all grounds, the turbo diesel shield is removed, the battery connections have all been checked(it always seems to have plenty of battery), i removed checked and cleaned the connectors to the ECM/PCM, changed fuel filter, replaced the fuel cap, checked for codes(there are none), double checked lift pump it functions as designed, cleaned all the relays and the the fuses with sandpaper.

Bill Heath has sent me a new PMD , on warranty. He is a good guy. I am still wondering if this is the problem.

I found this post on another site. My situation is very much the same.
http://gm-diesel.com/diesel/vbull/showthread.php?t=15661

Has anyone had this experience? Where it stalls and will not start and stalls, and it will only start when the glow plugs and other lights, and lift pump all the sudden come back online?

Thanks in advance.
 
Hmmm... seems to me you've done all the right stuff, so far. How about CTS switch? check the connector there, and if it does it again, pull the connector and see if that helps your glows cycle. The thread on GM-Diesel talks about a temp-inhibit switch; I don't really think we have one of those, but anything in that feedback loop could be causing the PCM to not reset.

You say you have checked all the grounds? That includes the engine-battery grounds, the block-frame straps, the block-chassis straps, and taking a few minutes to pull all your fuses, one at a time, and check the tangs to make sure they aren't corroded? This really sounds like one of those spooky grounding issues...

Check and clean every connection you can find. At best, it solves your problem. At worst, it's darn good preventative maintenance. I spent about 2 hours going over my truck with a wire-wheel dremel, a squeeze tube of dielectric gel, and some antiox, inspecting, cleaning, tightening every connection and ground I could find. I can't say for sure it solved anything, but it sure ruled a lot out.
 
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It sounds electrical to me as well. I believe Chris most recently has had the issue w/ the ignition switch. If you still had all the lights working on the dash I would say look at the lift pump. I would double check it anyway just because it only takes less than 20 seconds to do. Aside from the warning light issue it and the ops also cause stalling like you're experiencing.
 
I know from experience check the ground near the glow plug controller on the back of the motor and where it hooks to the fire wall. I would also check the on the passenger side frame near front tire. My truck had no glow plug light on occasion and the other lights would come on at weird times and the truck would stall. I had checked all grounds when I looked at the truck to buy it . When I got it home it started acting dumb so I checked all grounds again the two mentioned above the one was broke the terminal had pulled loose from the wire back of the intake near glow plug controller replaced the connector and wire cleaned and checked all others no more problems the one on the frame was covered in gunk of alll types oil, sand, mud, anything I have driven the truck in lately Jerry
 
I am voting for it too. Put new PMD on and truck died in about 50 feet. Bought IGN switch at dealer today for $260. Looks like quite a project to install. I am going to install it tomorrow.
Thanks all.
 
chrisk1500 said:
IGN switch is toast....
Click to expand...

My thoughts, and my problem also at one point.

Right down to the T with glow plug lights.

Now, it can't hurt you at all to open the under hood fuse box and pull / inspect / clean every fuse and relay there. A loose pcm fuse will give you similar symptoms, and is free to check.
 
I give up. Took the time to put in the ignition switch. Really thought i fixed it. I started the truck up let it idle for 4 hours and it did not die. Moved it outside of the garage, let it idle for 2 more hours, and it did not stall. Shut the truck off and let it cool down to 1 degree outside temp. Started the truck up and let it idle for another hour and then drove the truck all over the countryside, probably 60 miles or so, the truck did not stall. I then drove the truck back home from visiting famiily for the holidays, about 75 mile trip on the freeway, the truck did not stall even one time. Let the truck idle while i unloaded it and it did not stall.
I was so happy i thought i finally had it fixed. Started the truck up to warm it up before i headed to work this morning, truck did not stall. Started driving to work and truck stalled at a stop light, then stalled 3 times on the freeway.

I am going insane!!!!

I have checked all grounds, wiggled all wires, cleaned all relays and fuses with sandpaper, checked all pos, and neg battery connections. What else could it be!?

Any info would be greatly appreciated.
 
Time to start looking through wire bundles closely - especially the one that runs under the intake.

Look also at the bundle that runs by the A/C hoses - they tend to rub through.
 
Also closely check the ground wire on the IP.
Also the ground to the fender right at the battery.
You may have a corroded wire... They can corrode under the insulation -- No fun to find, but doable. A corroded wire will feel *funny* when you bend it.
If you have any soldered splices give them a close look too. They are very failure prone in automotive applications, but some folks (not manufacturers) like them anyway - Go figure.
Crimped splices can fail too if they weren't done correctly, btw.
 
As well - when it stalls, do the LP test immediately and see if you have fuel coming to the IP...
 
Time to use that 7 year warranty.
Every time I've had a PMD go out, I have run down everything else
I can try, just because I'm sure it can't be bad again, but it always is.
I'm new here, but been around the 6.5 for a while, on the other forum
that TD left (Hey Doc :biggrin:) not gonna go into PMD saga, but I'l bet
a dollar that's your trouble.

EDIT: Just saw that you changed the PMD after the trouble started -
was it new?
 
Harqobispal said:
I am voting for it too. Put new PMD on and truck died in about 50 feet. Bought IGN switch at dealer today for $260. Looks like quite a project to install. I am going to install it tomorrow.
Thanks all.
Click to expand...

Just a little FYI, O'Reillys has it for 150.00 in store brand,
or 173.00 for AC Delco
 
when you cycle the ignition, you get not glow plugs(WTS) light, no service throttle soon light, and no lift pump. The wierd thing is , if you wait usually 30 secs to 5 mins, all of the sudden these above mentioned devices reactivate, when you cycle the key. Then if you turn it all the way to start, the truck starts immediately. If those lights and devices do not come on , the truck will absolutely will not start.
Click to expand...

This doesn't sound like and FSD problem to me.
I believe there's a corroded or loose connection somewhere, or the ignition switch (or it's connector).

Next time it does it leave the key in the on position and starting beating on things (my first lesson as a TV repair apprentice - Really). I'd start with the steering column. If that doesn't do it start shaking wires, give the ECM a bonk. When you find the culprit the dash lights will come on......... I think.
 
Radioman that last post was the best. I have jiggled, checked beat on every connection i can think of. I REALLY DO READ THESE FORUMNS! I cleaned and inspected about 3 times every connection i have ever read mentioned here. The truck has a brand new PMD. The truck has a BRAND NEW ignition in it (I really thought i had it fixed with this, drove about 100 miles without a glitch). The ignition switch was not the problem. When i read your replies today, i went out in my office clothes(yes, i do work in an office with ties and such) , and trying not to get myself too oily started the truck up and agressively jiggled and shook every cable i could find. The ones under the intake the ones near the AC compressor, and every other harness in site. The truck just sat their idling perfectly. When i put that new ignition in it i took it out to a snow covered field after i beat on it to warm it up. It was a cornfield that had been plowed(turned over)before it snowed so it was very rough. I thew the truck in 4x4hi and took it all over bouncing around, it was quiite fun , and not even the slightest hiccup or glitch, or stall- i had the truck floored most of the time. The very next day i started the truck up to drive on the freeway to work. It stalled at 75mph 3 times, each time you would know the engine was dead, but the torque convertor was locked and a few seconds would go by and then it would roar to life. You would go about another 3 miles and BLAHHHHHH, dead, then wait a few seconds and it would start up again cause of the torque convertor.
This thing is really strange. I am starting to think ECM/PCM. I was all over that truck with the Fluke test meter checking grounds and voltages. Problem is when it stalls you are usually at a stop light or in the middle of the freeway and jumping out to do electrical checks is kinda outta the question, and usually the stall problem only lasts 30secs to 5 mins so you have to be really quick. Also it is extremely random so you are never prepared.
I am actually bringing it to a shop tomorrow. I have put a lot of time in and just dont have time now to mess with this anymore. It must be fixed, or at least someone else must be on the hook for not fixing it :).
I will be driving the 1992 Chev caprice classic until it is fixed.
I will DEFINATELY LET you all know if this gets fixed.
 
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Pull the DTC codes and see if there are any.

This could be a failing ECM.

When you replaced the Ignition switch, you no doubt had the batteries disconnected?
This could allow an anomaly in the ECM to correct itself and then after run time with power on the issue could be popping back up.

Checking the cables and other wiring to do with the batteries and the main chassis feed is always good.

These rigs dont like low voltage.

Be sure you have a good 14V to the chassis feed and at both batterries with the engine running.

The cables corrode inside where you cant see it and especially the grounds.

Good luck

MGW
 
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