LML glow plugs not working - Chevy and GMC Duramax Diesel Forum
11-16 LML Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 14 (permalink) Old 03-04-2018, 05:36 AM Thread Starter
 
Join Date: Dec 2017
Location: Moose Lake MN
Posts: 8
LML glow plugs not working

I recently bought a 2011 2500HD Duramax with PPEI Autocal & has been deleted. Love the truck but I'm having issues with the glow plugs. They are only getting 1 volt or under when key is turned on. I've replaced all the glow plugs with ones from Diesel RX, replaced the glow plug controller. (programmed the injector rates to the new module). I can't get the truck to start when its below 30 degrees. I've checked all the temp sensors & they are ok.
When the key is turned on the voltage will go to 3 volts briefly then down to 1 volt or under for several seconds. I hooked up a glow plug to the harness & it was barely getting warm at this voltage.

Any ideas?

2011 2500HD ext cab/ short box
LML/ Allison
PPEI Autocal
Flo pro 4" exhaust
Deleted.

1984 K20 Silverado
6.2L/ TH400
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post #2 of 14 (permalink) Old 08-30-2019, 06:07 PM
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Let's bump this up. My 2011 is doing the exact same thing.
-About 0.95 volts at the plugs (both on the stud and the harness' lug) when the plugs are 'on', triggered with a Tech II or by the ignition.
-Resistance on all plugs is good when checked with a mulitmeter and in the Tech II.
-No DTCs or CEL.
-Replaced GPM and flashed injector info. No change.

The plugs are pulse width modulated after the first two (2) seconds of operation. Could the ECM cause this?

Educated answers only please.
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post #3 of 14 (permalink) Old 08-31-2019, 03:34 AM Thread Starter
 
Join Date: Dec 2017
Location: Moose Lake MN
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JOKER, I replied to your pm, but am going to post here also for others to see.

My truck had been tuned by PPEI before I bought it. The first time I contacted them about the glow plug issue, they said they would not have been affected by their tuning. I had access to Alldata at the time so I got the schematic for the glow plug harness, inspected it, ohm'd each wire and load tested each wire. I had new A/C Delco glow plugs and a new Glow plug controller that had been programmed to the truck. That left only the PCM to be the problem. I contacted PPEI again explaining all that I had replaced & tested. They emailed me new files to upload to the autocal. I reprogrammed the truck with a new tune and the glow plugs seem to be working. Since then the coldest we have had is in the 20's, I'm waiting for a colder morning before I'm going to be completely convinced it's fixed though.

2011 2500HD ext cab/ short box
LML/ Allison
PPEI Autocal
Flo pro 4" exhaust
Deleted.

1984 K20 Silverado
6.2L/ TH400
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post #4 of 14 (permalink) Old 08-31-2019, 05:34 AM
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Right on, Ken. I got new tunes from my tuner as well, but the same issue is there.

I flashed the ECM to stock, flashed it with old H&S tunes, flashed it back to stock, and then again with EFI Live tune. Still under 1 volt with all of those flashes.

How much voltage are your plugs seeing now?
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post #5 of 14 (permalink) Old 09-02-2019, 05:04 AM Thread Starter
 
Join Date: Dec 2017
Location: Moose Lake MN
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I haven't checked voltage since the retune. The first morning below freezing (coming soon), I'll leave it outside overnight & check things out. I'll be sure to let you know.

2011 2500HD ext cab/ short box
LML/ Allison
PPEI Autocal
Flo pro 4" exhaust
Deleted.

1984 K20 Silverado
6.2L/ TH400
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post #6 of 14 (permalink) Old 09-04-2019, 12:38 PM
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Sounds good. As far as I know, the tuning doesn't effect glow plug operation. It would be nice to get it figured out though.
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post #7 of 14 (permalink) Old 09-04-2019, 07:10 PM
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This information pertains to my 2008 LMM. I'm assuming yours is much the same.



Glow Plug System Description

In the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Eight glow plugs are used as an aid to starting.

Control of the instant start system (ISS) glow plugs is accomplished by a glow control module unit and 4.7 volt glow plugs, requiring 2 seconds to heat up to 1,000C (1,832F). The temperature and the power consumption is controlled between the engine control module (ECM) and the controller within a wide range to suit the engine's pre-heating requirements. Each glow plug is energized individually. This capability yields more optimum heat times for the glow plugs, thus pre-glow times can be kept to a minimum for short wait to crank times and maximum glow plug durability. A DTC will set if there is a glow plug system fault.

A normal functioning system operates as follows:


  • Turn the ignition ON with the engine OFF, and at room temperature.
  • The glow plugs turn ON and heat up in 2 seconds and then are pulse-width modulated (PWM) for another 2 seconds.
  • The glow plug wait lamp is ON for 1 second during cold start.
  • The glow plug wait lamp may not illuminate during a warm engine start.
  • If the engine is cranked during or after the above sequence, the glow plugs may cycle ON and OFF after the ignition switch is returned from the start position, whether the engine starts or not. The engine does not have to be running to terminate the glow plug cycling.
The glow plug initial ON time will vary based on the system voltage and temperature. Lower temperatures cause longer ON times.

The ECM provides glow plug operation after starting a cold engine. This post-start operation is initiated when the ignition switch is returned to Run, from the Start position. This function helps clean up excessive white smoke and/or poor idle quality after starting.

Glow Plugs

The glow plugs are 4.7 volt heaters in each of the cylinders that turn ON, then pulse-width modulated when the ignition switch is turned to the RUN position prior to starting the engine. They remain pulsing a short time after starting, then they are turned OFF.

A Wait to Start lamp on the instrument panel provides information on engine starting conditions. The Wait to Start lamp will not illuminate during post-start glow plug operation.

Glow Plug/Controller

The glow plug controller is a solid state device which operates the glow plugs. The glow plug controller is connected to the following circuits:


  • The fuel heater ignition 1 voltage circuit
  • The battery voltage circuit
  • The CAN communication circuit located between the engine control module (ECM) and the glow plug controller
  • The engine ground circuit
  • The glow plug supply voltage circuits located between the glow plug controller and the glow plugs.
The glow plug diagnostic circuits are directly monitored individually by using a separate transistor to control current to each glow plug. Individual diagnosis is thus possible for every glow plug.
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Ron Nielson
2008 Silverado LT, CCLB, Edge Insight CTS
2009 Arctic Fox 29-5T, Silver Fox Edition, Onan 3600 LPG generator
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post #8 of 14 (permalink) Old 09-04-2019, 09:32 PM
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Question Glow Plug

Quote:
Originally Posted by Ron Nielson View Post
This information pertains to my 2008 LMM. I'm assuming yours is much the same.



Glow Plug System Description

In the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Eight glow plugs are used as an aid to starting.

Control of the instant start system (ISS) glow plugs is accomplished by a glow control module unit and 4.7 volt glow plugs, requiring 2 seconds to heat up to 1,000C (1,832F). The temperature and the power consumption is controlled between the engine control module (ECM) and the controller within a wide range to suit the engine's pre-heating requirements. Each glow plug is energized individually. This capability yields more optimum heat times for the glow plugs, thus pre-glow times can be kept to a minimum for short wait to crank times and maximum glow plug durability. A DTC will set if there is a glow plug system fault.

A normal functioning system operates as follows:


  • Turn the ignition ON with the engine OFF, and at room temperature.
  • The glow plugs turn ON and heat up in 2 seconds and then are pulse-width modulated (PWM) for another 2 seconds.
  • The glow plug wait lamp is ON for 1 second during cold start.
  • The glow plug wait lamp may not illuminate during a warm engine start.
  • If the engine is cranked during or after the above sequence, the glow plugs may cycle ON and OFF after the ignition switch is returned from the start position, whether the engine starts or not. The engine does not have to be running to terminate the glow plug cycling.
The glow plug initial ON time will vary based on the system voltage and temperature. Lower temperatures cause longer ON times.

The ECM provides glow plug operation after starting a cold engine. This post-start operation is initiated when the ignition switch is returned to Run, from the Start position. This function helps clean up excessive white smoke and/or poor idle quality after starting.

Glow Plugs

The glow plugs are 4.7 volt heaters in each of the cylinders that turn ON, then pulse-width modulated when the ignition switch is turned to the RUN position prior to starting the engine. They remain pulsing a short time after starting, then they are turned OFF.

A Wait to Start lamp on the instrument panel provides information on engine starting conditions. The Wait to Start lamp will not illuminate during post-start glow plug operation.

Glow Plug/Controller

The glow plug controller is a solid state device which operates the glow plugs. The glow plug controller is connected to the following circuits:


  • The fuel heater ignition 1 voltage circuit
  • The battery voltage circuit
  • The CAN communication circuit located between the engine control module (ECM) and the glow plug controller
  • The engine ground circuit
  • The glow plug supply voltage circuits located between the glow plug controller and the glow plugs.
The glow plug diagnostic circuits are directly monitored individually by using a separate transistor to control current to each glow plug. Individual diagnosis is thus possible for every glow plug.
Any idea on what ambient temperature the glow plugs become inactive?

2016 3500 HD Denali 4WD, CCSB, FuelBox 57 gallon Aux Tank, Edge Insight Monitor, Otherwise 100% Stock
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post #9 of 14 (permalink) Old 09-04-2019, 09:44 PM
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I don't know for certain, but I don't see even a hint of the glow plug light at temps above 65f on my LMM and my former LML on cold starts.

2008 Silverado 2500 Crew Cab Z71
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post #10 of 14 (permalink) Old 10-12-2019, 04:03 PM Thread Starter
 
Join Date: Dec 2017
Location: Moose Lake MN
Posts: 8
Joker, I left my truck outside last night as it was going to be in the 20's this morning. I got 4.9V at the glow plug when I turned the key on. . The voltage stayed at 4.9 for several seconds after the light went out, then dropped to zero. I tried it a 2nd time with the same results.

2011 2500HD ext cab/ short box
LML/ Allison
PPEI Autocal
Flo pro 4" exhaust
Deleted.

1984 K20 Silverado
6.2L/ TH400
Ken in MN is offline  
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