GP temp question
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Posting Guru
Joined: Dec 2004
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From: Virginia - SW (Riner)
GP temp question
What temp do the GP's come on at?
I know the PCM uses 3 sensors to determine if lighting the GPs is needed. It was 42 here this morning and I had to try a couple of times to get the 250 to start. Thought oh great time to look @ the GPR again but then I got to thinking - maybe it wasn't quite cold enough to turn the GPs on. Think I remember reading somewhere it was 40deg.
I know the PCM uses 3 sensors to determine if lighting the GPs is needed. It was 42 here this morning and I had to try a couple of times to get the 250 to start. Thought oh great time to look @ the GPR again but then I got to thinking - maybe it wasn't quite cold enough to turn the GPs on. Think I remember reading somewhere it was 40deg.
Postmaster
Joined: Jun 2009
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From: Monroe/Ellensburg, WA
I think a major factor in the PCM's decision to turn on the glow plugs is oil temp, If it sat overnight, the glow plugs would be on that morning...
I wouldn't base it soley on how warm/cold it was outside. That is a factor but not a huge one..
I wouldn't base it soley on how warm/cold it was outside. That is a factor but not a huge one..
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From: Virginia - SW (Riner)
IIRC - It uses 3 inputs to determine GP usage - oil temp, the baro sensor & the ambient temp sensor. In my case this morning oil temp equaled air temp since it had been sitting all night. What I can't find is the temp @ which the PCM turns on the GPR output. Its around 40 ish deg but I can't recall the exact temp.
Truck started on the 2nd try and did not smoke @ all. I quizzed a couple of other folks and 2/3 came back that they had longer crank times this morning too. This is the coldest morning we've seen since earlier in the year. Don't think all 3 of us suddenly have bad GPRs and we don't all get fuel @ the same place. Everybody nodded yes to using anti-gel of some sort.
Truck started on the 2nd try and did not smoke @ all. I quizzed a couple of other folks and 2/3 came back that they had longer crank times this morning too. This is the coldest morning we've seen since earlier in the year. Don't think all 3 of us suddenly have bad GPRs and we don't all get fuel @ the same place. Everybody nodded yes to using anti-gel of some sort.
Cargo Master
Joined: Feb 2010
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From: Delta, CO
I believe you are right on the 3 sensors that are involved.
maybe hook up a test lite to the GPR in the morning for the h@ll of it to see if it's asking them to come on. I know mine come on for a few seconds when it's 60*
maybe hook up a test lite to the GPR in the morning for the h@ll of it to see if it's asking them to come on. I know mine come on for a few seconds when it's 60*
Cargo Master
Joined: Feb 2010
Posts: 2,298
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From: Delta, CO
I believe you are right on the 3 sensors that are involved.
maybe hook up a test lite to the GPR in the morning for the h@ll of it to see if it's asking them to come on. I know mine come on for a few seconds when it's 60*
maybe hook up a test lite to the GPR in the morning for the h@ll of it to see if it's asking them to come on. I know mine come on for a few seconds when it's 60*
Lead Driver
Joined: Sep 2010
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my "gpr/led" lights up, every morning, even when it was summer. Weird thing is, sometimes in the morning ,especially in a rush, i do let it warm up, but dont wait for the light/s to go out, and the truck seems to start in a blink, but if wait for light/WTS to go out, then it takes 2-3 seconds...
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Posting Guru
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From: Virginia - SW (Riner)
Supposed to be just as cold in the morning - guess I'll be "under hood" meter in hand.... What's weird is 3 of us having an issue at the same time - go figure I guess.
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Posting Guru
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From: Virginia - SW (Riner)
Reading that tells me the GPR should energize unless the engine is hot.
This is just another reason to do the GPR LED mod
Weird that 3 of us had the same issue this morning although mine was the only one that req'd 2 tries to start.
This is just another reason to do the GPR LED mod
Weird that 3 of us had the same issue this morning although mine was the only one that req'd 2 tries to start.
Post Fiend
Joined: Nov 2007
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From: Payson, AZ
Also when you go out to start on a cooler morning, and truck was left outside, and the air temp might now be in the 60's, but if the overnight temps were in the 40s, the EOT may still be in the 40's. Ambient air temp will rise much faster than the temp of the oil. This is why the PCM uses EOT and not ambient air temp to decide on when and how long to operate GPR.
EDIT : And if anyone was wondering how hot the GPs get this is one I hooked up to a battery charger. The very tip was cherry hot in 3 seconds. The whole element was cherry hot in about 10 seconds.
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From: Virginia - SW (Riner)
We all pretty much got in & started them up at the same time - we all work together. I knew it was colder this am so I waited 15-20 seconds after the WTS went out to start cranking. The other 2 just cranked longer than I did. I don't like to crank more than 20-30 seconds since that's hard on the starter&batteries. I quit cranking, cycled the key and waited for the WTS again then it started.
Welcome to fall
Welcome to fall
Lead Driver
Joined: Sep 2005
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From: Norco,CA
Again great pictures and information Robin. I know when I go to Wyoming hunting and the truck sets a week at a time I wait till light goes out about 20 seconds then do it again and it starts right up. I had trouble once with a rough idle for a minute or so over the years but it was -15 the night before.The led light would help alot because you know how long the glow plugs are on. And yes the wait to start comes on even at 115 outside if the truck sets.
Chet
Chet
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Again great pictures and information Robin. I know when I go to Wyoming hunting and the truck sets a week at a time I wait till light goes out about 20 seconds then do it again and it starts right up. I had trouble once with a rough idle for a minute or so over the years but it was -15 the night before.The led light would help alot because you know how long the glow plugs are on. And yes the wait to start comes on even at 115 outside if the truck sets.
Chet
Chet
