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Glow plugs on 2025 Cummins

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teton10

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I noticed on my 2025 Ram 2500 with Cummins that in cold weather (sub-freezing temps as low as 13 degrees) there is no delay between me pushing the start button and the engine starting - same with remote start. The engine runs rough for about 5 seconds then smooths out. It leads my to think that the glow plugs are not warming up. The dealer says that there should not be any delay in starting and that the glow plugs work immediately. Anyone else have this situation or have you heard that this is normal? Definitely different than the 6.7 with grid heater. Thanks
 
teton10 said:
I noticed on my 2025 Ram 2500 with Cummins that in cold weather (sub-freezing temps as low as 13 degrees) there is no delay between me pushing the start button and the engine starting - same with remote start. The engine runs rough for about 5 seconds then smooths out. It leads my to think that the glow plugs are not warming up. The dealer says that there should not be any delay in starting and that the glow plugs work immediately. Anyone else have this situation or have you heard that this is normal? Definitely different than the 6.7 with grid heater. Thanks
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Cummins is having some issues with the glow plugs causing shorts / short-cycling.

When you attempt to start, are you holding your foot on the brake pedal? Have you tried keeping your foot off the pedal? Any check engine lights or trouble codes ?
 
Thermodynamics would dictate it would take time for the glow plugs to reach optimum temperature to help ignite diesel fuel thus starting the combustion cycle (more then a few microseconds which is currently set). IMO not having a delay tied to outside ambient temperature in the ECM is incorrect and probably an oversite. Have you tried adding your own delay? For example, turn on ignition but don't press brake pedal to start?

I currently have a F-450 that has glow plugs. On very cold mornings it adds a delay before engaging starter motor.
 
mbarber84 said:
Cummins is having some issues with the glow plugs causing shorts / short-cycling.

When you attempt to start, are you holding your foot on the brake pedal? Have you tried keeping your foot off the pedal? Any check engine lights or trouble codes ?
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The engine starts immediately even if it's sat all night and it's 15 degrees when starting. No delay for the glow plugs to warm and a rough running for about 5-10 seconds. The dealer is saying that the glow plugs are always on but I know that's just not true. I often remote start the truck as it sits under a shed roof about 70 feet from our house. It starts immediately without a "glow plug" delay in sub-freezing weather. i am used to my 2022 and previous trucks with grid heater that delay for a few seconds before cold weather starting.
 
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Push the start button without foot on the brake. Your glow plugs will kick in and warm for about 10 seconds. Then start as normal
 
teton10 said:
I noticed on my 2025 Ram 2500 with Cummins that in cold weather (sub-freezing temps as low as 13 degrees) there is no delay between me pushing the start button and the engine starting - same with remote start. The engine runs rough for about 5 seconds then smooths out. It leads my to think that the glow plugs are not warming up. The dealer says that there should not be any delay in starting and that the glow plugs work immediately. Anyone else have this situation or have you heard that this is normal? Definitely different than the 6.7 with grid heater. Thanks
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I noticed that on my 2025 5500 as well, push start without your foot on the pedal and wait, this solves 2 problems. Allows plugs to heat up and charges fuel system which prevent excessive cranking with the known air capture in the fuel filter housing
 
Just caught a video showing the glow plug light will come on if you press ignition button and no brake. When ready to start the the glow plug light will turn off then press start again with brake. So as I said before - I think a delay was overlooked and will be added back in on future ECM updates. I would manually watch for the light and start afterwards on cold starts. Avoid remote start for now.

EDIT: Found the video. Start around 1min mark.

 
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How was the delay overlooked? You literally push the button without your foot on the brake and it warms up and tells you to start it. Seems clearly engineered that way. If you need the truck to bypass the glow plugs then put your foot on the brake and start it.

Seems like it's working perfectly to me. When it's cold I hop in, push the button, buckle and check Android Auto for a second and then it says start truck and I do. It fires right up.
 
The owners manual has a section on cold weather start up and plugging it in to keep it warms for easier starts and less wear in case that is interesting.
 
Forceofwill said:
How was the delay overlooked? You literally push the button without your foot on the brake and it warms up and tells you to start it. Seems clearly engineered that way. If you need the truck to bypass the glow plugs then put your foot on the brake and start it.

Seems like it's working perfectly to me. When it's cold I hop in, push the button, buckle and check Android Auto for a second and then it says start truck and I do. It fires right up.
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There is no delay when remote starting unlike previous year Rams. Ford does same. Guess you can drink ram koolaid and think they intended it that way but I stand by my point it was an oversight and will be fixed in future updates.
 
HDFarmer said:
I noticed that on my 2025 5500 as well, push start without your foot on the pedal and wait, this solves 2 problems. Allows plugs to heat up and charges fuel system which prevent excessive cranking with the known air capture in the fuel filter housing
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Your 2025 should be priming the fuel system the minute you open the door. They’re programmed that way for 25+, which is why they recommend disconnecting the batteries when you’re replacing fuel filters.
 
That makes me curious if they also tied that door open action to the glow plugs? maybe they are smarter than we give them credit.
 
NDanecker said:
Just caught a video showing the glow plug light will come on if you press ignition button and no brake. When ready to start the the glow plug light will turn off then press start again with brake. So as I said before - I think a delay was overlooked and will be added back in on future ECM updates. I would manually watch for the light and start afterwards on cold starts. Avoid remote start for now.

EDIT: Found the video. Start around 1min mark.

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Thank you for the information - makes sense to me. The dealer last week told me there is no need for the delay with glow plugs. SMH.... :)
 
My old 2017 glow plug equipped F350 started like a gasoline powered vehicle. Even in -20°F weather there was virtually no delay. It had over 300,000 miles when I traded it in.
 
teton10 said:
Thank you for the information - makes sense to me. The dealer last week told me there is no need for the delay with glow plugs. SMH.... :)
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Guy is a master tech at Ram dealer so I hope he knows what he's talking about with these trucks.
 
NDanecker said:
There is no delay when remote starting unlike previous year Rams. Ford does same. Guess you can drink ram koolaid and think they intended it that way but I stand by my point it was an oversight and will be fixed in future updates.
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I'm not drinking Ram coolaid lol. But if you're only specifically talking about remote start, then yeah I agree they should probably have a temperature set point for them to kick on before starting. I don't have remote start so mine works fine.
 
I am sure you will be able to bypass it by pressing the button a second time like the previous years with grid heaters preheating.
 
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