Glow plug wait to start light.
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Fleet Mechanic
Joined: Apr 2011
Posts: 1,441
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From: Marseilles IL
Glow plug wait to start light.
Hello I have a question about my 2013 6.7. It’s in the teens and when I cold start my truck the glow plug light only goes on for a couple seconds and it seems like the glow plugs may not be working? Is it normal for the light to only be on for a couple seconds? Truck starts but sounds a but rough at first. Is this normal or is there something I need to look at? Thank you!
FTE Legend
Joined: Mar 2017
Posts: 31,880
Likes: 9,172
From: Western NY
Hello I have a question about my 2013 6.7. It’s in the teens and when I cold start my truck the glow plug light only goes on for a couple seconds and it seems like the glow plugs may not be working? Is it normal for the light to only be on for a couple seconds? Truck starts but sounds a but rough at first. Is this normal or is there something I need to look at? Thank you!
Cross-Country
Joined: Nov 2024
Posts: 60
Likes: 20
Modern glow plugs reach >2k° in under 3 seconds. Additionally, the light on is the minimum wait time the PCM/ECU decide on, it's not indicative that the glow plugs themselves are actually powered/active. They can cycle on/off even while running if needed (they're self-regulating). If you try to start and the PCM doesn't think it's ready yet, it won't crank. The diesel supplemental covers this though not in great detail. I'm not sure how cold it's been for you, but I wouldn't expect this to be related to it running roughly.
If you're really wanting to see operating, you can get at the module - it's under the passenger battery tray. Easy way to get at it is pulling the wheel liner.
If you're really wanting to see operating, you can get at the module - it's under the passenger battery tray. Easy way to get at it is pulling the wheel liner.
FTE Legend
Joined: Mar 2017
Posts: 31,880
Likes: 9,172
From: Western NY
Modern glow plugs reach >2k° in under 3 seconds. Additionally, the light on is the minimum wait time the PCM/ECU decide on, it's not indicative that the glow plugs themselves are actually powered/active. They can cycle on/off even while running if needed (they're self-regulating). If you try to start and the PCM doesn't think it's ready yet, it won't crank. The diesel supplemental covers this though not in great detail. I'm not sure how cold it's been for you, but I wouldn't expect this to be related to it running roughly.
If you're really wanting to see operating, you can get at the module - it's under the passenger battery tray. Easy way to get at it is pulling the wheel liner.
If you're really wanting to see operating, you can get at the module - it's under the passenger battery tray. Easy way to get at it is pulling the wheel liner.
Last edited by Overkill2; Dec 15, 2024 at 04:59 PM. Reason: Correct post
Cross-Country
Joined: Nov 2024
Posts: 60
Likes: 20
Hah! I had time on my hands. I got frustrated at not finding my OEM auxilary/upfitter switch wires under the dash at all, so came on here and decided to try to be helpful 
Always appreciate your inputs - sometimes less words is better
Always appreciate your inputs - sometimes less words is better
FTE Legend
Joined: Mar 2017
Posts: 31,880
Likes: 9,172
From: Western NY
Haha... no way man... Your response made sense because the ECM with the temp sensor I'm sure determines how long the glow plugs stay on, so like you said, he may have something else going on...
Tuned
Joined: Feb 2019
Posts: 278
Likes: 183
ARod just did a video related to glow plug diagnostics and mentioned that the plugs stay lit up to 120 seconds if the engine temps are below 120-130.
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Fleet Mechanic
Joined: Oct 2022
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From: Dallas Metroplex
Well, apparently that video requires a logon to a YouTube account to watch (which I do not have, nor want). Any way you can embed the video in a post, instead of linking directly to the YouTube page?
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Tuned
Joined: Feb 2019
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Updated the link. PTT isn't a private YouTube channel, so not sure why it wanted you to login.
Lead Driver
Joined: Feb 2022
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If a glow plug or more fail, it will set a code and may also throw a CEL. Toss a scanner on it and see if you got any codes. Something like P067x where x is the number of the cylinder having an issue. Could also be a bad module.
More Turbo
Joined: Oct 2023
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As pointed out the plugs do run after the light is off. Any diesel ive owned or own with glow plugs, Ford or other brands is set up this way. When the light goes out the computers minimum chamber temp for starting has been met. It still may be too cold for a smooth start though and stumble a bit.
The teens are where my 6.7s always started to have cold start stumbles if turned over to quickly and especially if they sat for more than 2 days frozen.
The teens are where my 6.7s always started to have cold start stumbles if turned over to quickly and especially if they sat for more than 2 days frozen.
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