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No glow plug light and won't start.

Sinners Saint

Sinners Saint

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Location
Houston, Texas
Tried to crank the truck today and the the glow plug light never came on. It turns over but won't start. It's been starting fine the past few days, but the glow plug light would only come on for a few seconds. I checked the fuse and it's not popped, but there is no power coming to it when I checked it with a test light. I just put a brand new glow plug controller/relay on it a few weeks ago when I was having a problem with it. But that was all from a shorted fuel heater. I unplugged the heater and it has started fine without it. I still have the old GP controller and will try to ut it on and see if that does any good, but I been sick today and don't think I'll get to it tonight. Anyone have any ideas?
 
The only reason I have'nt checked the grounds is cause I just cleaned the and redone them a few weeks ago, But I will check them out tomorrow morning. Certainly makes sense.
 
In the 94 its actually just called ECM, and its under the steering column. The only fuse under the hood is the lift pump fuse.

More than likely you just have blown ECM fuse just like Crankme said.
 
buddy said:
In the 94 its actually just called ECM, and its under the steering column. The only fuse under the hood is the lift pump fuse.

More than likely you just have blown ECM fuse just like Crankme said.
Click to expand...

Absolutly. I worked on a 6.5 down on LI where the guy changed THE IP and all it was the ECM fuse. Symptoms excatly as you describe. You can hook a scanner to it and see if it reads the ecm. If it can't ecm fuse or ECm itself.
 
I started cleaning the grounds from the frame to the engine and cab. Got the contacts at the frame clean and I can't get to the ends attached to the back of the head or the cab, so I decided to go with a hunch. I recently replaced the glow plug controller. It turned out that it wasn't the problem before so I left the new one on there anyway and kept the old one for a back-up. I swapped them out and BAMMO!!!!!!!! The WTS light came on and the truck cranked right up. And the pisser of it all is I can't find the reciept to return the faulty new GPC. But at least the damn truck is backon the road.
 
I have a 94 GMC 3500, 6.5TD reg cab LB, all stock except pmd cooler. 500k km and runs great. Recently replaced GPC because of short glow plug on time. Fixed that problem, but after a few starts, glow plugs won't come on, no WTS light, cranks but no start. DTC 29 code. GPC has power on A terminal, C terminal is good ground, no signal from PCM to B terminal. Probed pin C13 (yellow wire) at PCM, no signal. I've cleaned all ground connections, replaced batteries and coolant sensor. Ign., gauges., GP and PCM fuses good. Tried 2 different PCMs with my eprom with no luck. PCM will not generate a signal to the GPC. After 3 days troubleshooting, I'm going nuts. Any ideas?
 
jefferson said:
I have a 94 GMC 3500, 6.5TD reg cab LB, all stock except pmd cooler. 500k km and runs great. Recently replaced GPC because of short glow plug on time. Fixed that problem, but after a few starts, glow plugs won't come on, no WTS light, cranks but no start. DTC 29 code. GPC has power on A terminal, C terminal is good ground, no signal from PCM to B terminal. Probed pin C13 (yellow wire) at PCM, no signal. I've cleaned all ground connections, replaced batteries and coolant sensor. Ign., gauges., GP and PCM fuses good. Tried 2 different PCMs with my eprom with no luck. PCM will not generate a signal to the GPC. After 3 days troubleshooting, I'm going nuts. Any ideas?
Click to expand...

Check the ECM fuse? Not sure if that exist in a 94.
 
Okay, problem solved! After cleaning all the ground connections, I started to check continuity between battery negative and each ground. Found the PCM ground stud near the back of the RH intake manifold did not have continuity, despite cleaning. Moved the ground to the rear most stud and got a good connection. During my circuit testing, I discovered one of my jumper wires (brand new) had intermittent continuity. A reminder to check the integrity of all test equipment before trying to diagnose results. Thanks to everyone for your input.
 
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