I have been having problems with my 96 GMC 6.5l turbo diesel. Every now and then the glow light does not turn on, on cold days (usually ~mid 40's degrees F). Everything else turns on, the instment panel lights, the lights, and it cranks over like normal, but nothing happens when the engine is cranked over. No signs of the engine trying to light up. But once the day warms up (~70-80 degrees F) when I get home from work, it start up like normal. I have changed the PMD twice, and have added a cooler (it was bad), have relocated the OPS to the return line on the turbo, have replaced the shut off solenoid and the glow plug relay.

I was reading another tread and someone described the prolems with the ECM, and it sounds liked like the ground on the ECM. How Would I check that? I took the EMC out from behind the glove and tired to pull off the plugs to make sure they had good contacts. I got one off, but the other one cracked from one of the corners, so I left them alone. Is there any way to check if it's the groundconnection that's bad?

The symptoms that let me to believe that its the EMC ground, is that when it does start up after a "no start" morning, it gives a series of short glow plug cycling (shorted then a second). Once the ignition is turned on and off, the cycling returns to the normal 5 second cycling.

Any advise would be apperciated. Thanks



1. Does the engine crank, or 'turn over'? Yes
1a. Does the engine start and run? Yes, on warm days.
1a1. do you have fuel? Yes
1b. Do you have a Wait To Start Light & the amount of time (seconds) lit.
Does not light up on cold mornings.
1c. Ambient Condition (temperature outside indicate F or C) 45°C
1d. Engine Cranking speed Normal, new starter.
1e. Are you experiencing stalling? Has only stalled once after 5 mins of running but thats the only time that's happened. Then it started as normal 5 min later, after the short glow plug cycling
1g. If Stalling, do you notice loss of dash or instruments?
Only once and the dash lights turned on like when turning the key and waiting for the glow plugs to cycle. The PMD and cooler are bolted on the intake (I did't buy the extention) New PMD.
1i. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now? No
1.1 Lift pump test - New lift pump
2. Service Engine Light while running?- intermittent
3. Model year 96
3a. Odometer reading 260,000 miles
4. Have you scanned for engine codes? (varies by pre/post 96) no
6. Air Filter condition Good
7. Fuel filter condition freshly changed
8. Condition of Battery terminal connections new batteries (6 mothes old) terminals clean
8b. Are batteries of differing age or are they a matched set? Matched set
8c. Condition of Major Grounds. (same drill as batt - removed, cleaned, retightened) unknown
9. Upon cold start, does the radiator hose get hard quickly? Yes
10. Upon cold start, do you have excessive white smoke? no
11. Do you have excessive cranking time before the engine starts? When the glow plugs work no, when the glow does not work, it doesn't matter how long the engine is cranked for, it does not start

12. Have you used the block heater, and does this effect engine starting?Have not used it
13. During hard acceleration, do you have excessive black smoke? Yes
14. Do you have any unusual exhaust smoke issues? no
15. Turbo check out - pass
16. Do you have an EGR on the engine? Don't know
17. Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD. K2500
18. Indicate fuel that you are using: #2 Diesel
19. Are you using any fuel additives? No
20. Please indicate geographic region you are in: Los angeles, Califionia
21. Do you have any service history available that might pertain to the problem you are having? No
22. Please indicate any modifications to the vehicle that might help us diagnose better. No mods, all stock.
23. Upon unscrewing the fuel cap, do you have a large vacuum formed in the tank? no
24. Location of PMD/FSD? remoted over intake
24a. If remote mounted, describe wiring harness (homemade or purchased from a vendor?) the stockharness
24b. Indicate the location and condition of the FSD/IP grounding wire. Stock wire bolted on the cooler
25. Are ALL glow plugs in proper working order as per this thread? yes

Like this?

Cold start attempt (http://www.youtube.com/watch?v=fvGgBrjWERA)


Warm start (http://www.youtube.com/watch?v=8rNLMbe5_uw)


If this is the same problem that I had, i needed a replacement ECM to solve it.
I believe there's a warranty from GM on the ECMs. I've heard only little bits and pieces of this, but i'll check around.

dave is that your voice?

Yes exactly like that. That was my next step. Would taking the car to the dealer or a shop to be reflash the ECM be the same as replacing it, to aviod cracking the plugs? Or should it just be replaced?

Like this?

Cold start attempt (http://www.youtube.com/watch?v=fvGgBrjWERA)


Warm start (http://www.youtube.com/watch?v=8rNLMbe5_uw)


If this is the same problem that I had, i needed a replacement ECM to solve it.
I believe there's a warranty from GM on the ECMs. I've heard only little bits and pieces of this, but i'll check around.
First time I have seen these vids. But my first thought of things to rull out would be the ign switch. If it were your problem yours would be the easiest to see the problem. The 4 wires at the plug that should have 12 volts with the key in the run pos. are pink, white,org,brn. If this were your problem 1 of those would show 0 volts.

First time I have seen these vids. But my first thought of things to rull out would be the ign switch. If it were your problem yours would be the easiest to see the problem. The 4 wires at the plug that should have 12 volts with the key in the run pos. are pink, white,org,brn. If this were your problem 1 of those would show 0 volts.

Ign switch was new in these vids(they are mine), grounds were good, PMD isolator installed. All that was checked sadly and the issue got worse to the point of random PCM power loss on the road and the engine wouldn't start(with the same issue as first video) then the PCM would randomly get power back and it'd be fine for a little bit.

The cold seemed to affect it too. when it got below ~35-40 degrees i'd have the problem all the time. When it was warm outside the truck wouldn't so much as hiccup.

dave is that your voice?


:o: that would be me winter 07 with one hell of a cold. :p:

Ign switch was new in these vids, grounds were good, PMD isolator installed. All that was checked sadly.
I gave you credit for all that. I am not even going to go look it up for any thing more than the vids. But it is still possible for him. But no means a given.

I will check the ignition before I change the ECM. Thanks

I gave you credit for all that. I am not even going to go look it up for any thing more than the vids. But it is still possible for him. But no means a given.

Ok. :p: ignition switches do wear out eventually because of arcing internally when the contacts connect and disconnect. I'd say look into it. My factory ignition switch was bad. When the truck dies on you check to see if the dash goes out(no lights, etc). That points to a bad ignition switch.

I will check the ignition before I change the ECM. Thanks

I'd look into this ECM warranty thing if yours turns out to be bad. I hope you don't go through what i did. It certainly creates headaches.

Ok. :p: ignition switches do wear out eventually because of arcing internally when the contacts connect and disconnect. I'd say look into it. My factory ignition switch was bad. When the truck dies on you check to see if the dash goes out(no lights, etc). That points to a bad ignition switch.



.


I have seen many diffrent ways that they fail. They are 6 switches inside. They act diffrent for each 1 of those switches. But if you have 1 of them that will not turn at all. Those are cut and dry to see with a meter When the in this case glow light dosent come on.

I have seen many diffrent ways that they fail. They are 6 switches inside. They act diffrent for each 1 of those switches. But if you have 1 of them that will not turn at all. Those are cut and dry to see with a meter When the in this case glow light dosent come on.

I wish i knew this before i just started throwing money at the truck. :o:

I learned the easy way. I still go to the school of hard knocks. But have started to look at the odd problems through the whole gm line To see if all the problems share 1 of those switches.

And a friend of mine was having a friend chase a cold no start in his s-10. He did decide that it would start if he put a heater inside the truck for 20 mins. crank sensor, ecm,inst cluster,body mod,cam sensor, ign mod later. He started to think about what I told him and found it would start in 5 min if he held a blow drier near the ign lock. So he put in he new switch. Never failed to start after that no mater how clod it got.

I hope your list didnt look like this 1.

Not yet but getting close.

it gives a series of short glow plug cycling (shorted then a second).

Is that IT - Or does it cycle AFTER doing the 5 second cycle. Cycling on / off AFTER the intial glow cycle is what it's supposed to do...

it gives a series of short glow plug cycling (shorted then a second).

Is that IT - Or does it cycle AFTER doing the 5 second cycle. Cycling on / off AFTER the intial glow cycle is what it's supposed to do...
Unplug the CTS and see if your glow times come up to like 10 seconds.

Also --- The FSD ground NEEDS to be on the IP - NOT on the heat sink!

Sorry about the double -- I don't know what I did??????????????