Glow plugs are on during warm starts

[Trip]

With 8900 miles on my 03, the glow plugs, just yesterday, started performing normal cold lighting procedures during successive warm starts. It's never done this before. Engine was off and at temperature, and when the key is turned on, the glow plug light on the dash stays on for quite some time. Then when the engine fires, it seems like either over-fueling or a high idle for just a few seconds, then settles down to idle. I've got my manuals out to see about diagnosing, but has anyone had similar symptoms?

[Gbenzx01]

Trip,

Sounds like a new one no one has had before & just bumping you thread sense I wonder too.
:confused:
Gben

[Trip]

Gben
Thanks for the interest. I'm here in Henderson, NV, and the temps at night are getting close to freesing, so I was using the block heater for an hour or so in the morning to warm it up. Worked great for a couple of weeks, and then one morning, nearly a minute after I started the truck, the idle came down and was incredibly irratic. Had to throttle up to 1000 rpm or so to smooth it out. It was that day, with each warm start, the glow plugs ran a complete cycle. Truck would then start and idle back down really rough again. Once the truck warmed up, it ran great. This went on for a couple more days until I decided not to plug her in to see what happen. Sure enough, normal start, normal idle, and glow plugs did not run a complete cycle on warm starts. Everything went back to normal. So now I don't use the heater, and everything seems fine. Real confusing. Just wanted to let you know the latest, as this didn't stir much interest. Again, thanks for your reply.

[jesshd]

DOn't know the for sure answer, but it seems like the engine is getting warm with the heater, but whatever temp sensor tells the PCM to use or not use the glow plugs is still sensing that the engine is cold and not warmed up. I don't know what sensor the engine uses for the temp sense for the glow plugs, or even if it is separate, but I am sure that it would cause the situation you describe if it was not sensing that the engine is warm. Just a guess.

Jess

[Runaway]

Would have to concur with "jesshd." If you are plugging in at 32 degrees, more than likely its confusing the computer as to what it should do. Personally I don't feel you need to plug in at that warm a temperature. I've had two Dodge's with the Cummin's and this Dmax and have yet to unwrap the cord to the block heater. Started the Cummins at -20 a few times and the Dmax at -10 last winter. These new diesels are not in the same class of those of yesterday. My opinion of course :D

[JustWondering]

Hey Trip,

It appears that I went through the exact same condition you're describing about 2 weeks ago.
I took the truck to the dealer for an alignment, when picked it up later on the day, first thing I noticed when I started the truck was a surge in the rpm's. The engine reved up to 1,000 -1,1000 rpm and almost immediatly settle down to 650. I also noticed the glow plug light came on even though the temperature gauge was reading about 180.
This condition persisted all day long during several starts.
Then the next day, poof...it was gone! Everything back to normal, hasn't done it since :confused: .

[AlanL]

I plug my truck in every night from Mid October through until the end of March... then use a remote starter in the morning. The cord is on a timer, so the truck is plugged in for about 3 hours prior to being started.

At work it sits out all day (no plugs in the parking lot) and I start it in the evening with the remote starter and let it run for about 10 minutes before I leave.

So far I've had no problems at all.

Even though plugging the truck in isn't *necessary* it certainly helps get the heat going more quickly in the morning.

-Al

[dl537]

I had the same problem and took it into the dealer. The sensor was reading the outside temp at -40 degrees and was compensating with sending too much fuel for a normal start. Very simple fix with a sensor change.

[Trip]

Thank you all for the input. It certainly helps to get multiple suggestions. I appreciate it!