Glow plug light staying on too long, hard start.

[clys]

Hey guys. Got a customer truck with a hard start condition. The glow plug light comes on, and stays on for about 10 mins until the truck has reached operating temp...something I've never seen in a 6.0 before.

I know the Beru glow plugs never fail, and even if one did, I don't think it would cause the extended wait to start light illumination...so I've kind of ruled out a glow plug failing.

So of course the next step would be to look at the Glow Plug Control Module, again, something I've never had to replace, but is what I'm leaning to as the culprit of this issue, what do you guys think?

I leaning on the GPCM on the assumption that the glow plug system is contained to the GPCM only, and not other sensors. Basically what I'm asking is: could it be maybe just a faulty ambient air temp sensor causing the glow plugs to stay on for too long? But then again, this wouldn't cause a hard start...

Either way, let me know what you guys think, haven't run into this one before!



Thanks





Clyson

[dannyboy950]

First off how cold of an environment, sub freezeing temps or what. How good a shape is the engine/compression. If it is really cold it actually may be working correctly if the block/water doesn't get up by then.
I would supect the engine temp sensor readings more than the ambient temp.
Compare actual temp readings to recorded temp readings, a hand held digital thermometer is good for this. Shoot the block, heads and hoses and radiator and compare readings.

[clys]

Originally Posted by dannyboy950

First off how cold of an environment, sub freezeing temps or what. How good a shape is the engine/compression. If it is really cold it actually may be working correctly if the block/water doesn't get up by then.
I would supect the engine temp sensor readings more than the ambient temp.
Compare actual temp readings to recorded temp readings, a hand held digital thermometer is good for this. Shoot the block, heads and hoses and radiator and compare readings.

Yes sub freezing. I work on on average 3 different 6.0L's a day in and out and I've never seen one do what this one's doing with the wait to start light in this climate.

Anyone seen/heard of the GPCM failing?

[dannyboy950]

Yes they do fail sometimes. They are an electronic device even tho solid state they do fail.

[VeeDubTDI]

Did you figure out the cause of your problem?

Glow plug time is calculated based on engine oil temperature. I saw a graph somewhere, but haven't been able to find it. If anyone knows which graph I'm talking about, please post it.

[fordmasterdieseltech]

they are known for melting the green connector on the gpcm like the later 7.3. remove both connector and inspect for burnt or melted pins.

[clys]

Replaced the GPCM and all is well.

[97 crewcab]

I have a 97 7.3 and the wts light stays on and doesn't go off at all. Could this be from a pcm-idm communication error? I haven't gotten to drive my baby in a month and am lost with this truck.

[Newman]

Originally Posted by 97 crewcab

I have a 97 7.3 and the wts light stays on and doesn't go off at all. Could this be from a pcm-idm communication error? I haven't gotten to drive my baby in a month and am lost with this truck.

You may have better luck asking about this in the 7.3 area.