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Duramax 6600 Discussion Forum for the Duramax 6600 Diesel Engine, including the LB7, LLY, LBZ & LMM engine specific topics.

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  #1  
Old 06-11-2011, 05:33 AM
EdSpaek EdSpaek is offline
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Default Cylinder 7 glow plug failure code

My 2008 LMM lit the service engine light last evening and when I read the codes it indicates the glow plug for cylinder 7 has failed. I reset the code and it has not returned for several starts now. Does this make any sense. I have not read the resistance of the number 7 glow plug yet- plans to do so later today. Engine only has 78,000 miles on it. The Weather has been in the high 90's the past few days and I have been doing a lot of high speed driving and a fair amount of idling to stay cool, wonder if this has had any affect on the glow plugs or associated electronics
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  #2  
Old 06-11-2011, 10:32 AM
DmaxMaverick DmaxMaverick is offline
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Sounds normal. Glow plugs fail. Rarely is there a specific reason, short of excessive glow times. They just quit. It's a fact. Your highway driving and idle periods are not likely a factor, or we'd see a lot more failures. Your one plug may or may not be bad, so you should verify by testing. The PCM monitors the GP/heater system under specific conditions. On earlier models, if the sensed ambient temp and/or coolant temp is above 63F, it isn't monitored. I don't know what the monitoring temp is on the later models. If your temps remain above this, you may not get a code, even with a failed plug.

Plugs fail for a variety of reasons. It is important to pull it if it's failed, to verify it isn't physically damaged, which could lead to pieces of it falling into the cylinder. If it appears intact, leaving it in will cause no damage, and only be an inconvenience when the SES indicator becomes annoying.
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Old 06-11-2011, 04:36 PM
EdSpaek EdSpaek is offline
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Default Glow plug

Thanks for the info, had a second code show up after a cold start this afternoon so I disconnected the glowplug and had a resistance of 400 ohms so I replaced it and all is well. Do have a question, where is the sealing surface on the glowplug. I do not see a tapered surface only a flat surface where the heating element of the plug leaves the housing. Is that where it seals?
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Old 06-11-2011, 04:55 PM
DmaxMaverick DmaxMaverick is offline
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It seals on the shoulder where the element exits the body. Unlike spark plugs, this keeps the threads out of the combustion chamber.

At 400 ohms, the plug should be good. They usually fail open. Put 12V on it and see if it glows. If it does, the problem may have been the connector.
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  #5  
Old 06-12-2011, 04:32 AM
EdSpaek EdSpaek is offline
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Default Glow Plugs

I will give that a try, the connections were fairly corroded so I removed all of them from bank one and cleaned and retorqued them
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  #6  
Old 06-12-2011, 06:27 AM
Kennedy Kennedy is offline
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Suggestion: Dielectric grease

That and frequent "bathing" to remove road salt.
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  #7  
Old 06-19-2011, 02:52 PM
EdSpaek EdSpaek is offline
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Default Glowplugs on a 70 degree morning

Never noticed the glow plug lamp on for 2 seconds or so in previous years when I turned the key to the start position and the morning temp was 65-70 degrees F

Anyone know if this is normal

Ed
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Old 10-11-2011, 02:18 PM
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Stlheadake Stlheadake is offline
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I RARELY see my light anyway unless it is below 40F degrees or so. Even when it is cold like 25f it only comes on for a second.

I am getting a code too, and would like to piggy back on your post. I DON'T want to hijack it!! I am getting a code on number 4. Is it ok to change just the one, or should I change all?

Scott
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Old 10-11-2011, 03:49 PM
DmaxMaverick DmaxMaverick is offline
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Glow plugs can be changed one at a time, as needed. There's no need to replace good plugs, as you/we have no way of knowing how long they will last. Some old plugs last forever, while a new plug might last a week. They work, or they don't. Having a spare is handy, but not at all required, like for older machines (6.5/6.2/6.9/7.3, they won't start cold without them). Your truck will start, however sloppy, down to some amazingly cold temps with no plugs at all. I cold-soaked my 2001 for 8 hours at -10 once. I unplugged the plug harness, just to see if it would. Normal cranking time and she fired, ran rough and smoky for about 20 seconds, then normal. That was with all 8 disabled. If only 2 or 3 were out, I probably wouldn't notice, except for the SES lamp.
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Old 10-11-2011, 04:21 PM
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Stlheadake Stlheadake is offline
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Thanks for your reply. I'll only replace number four. But to be certain, number four is on the passenger side rear yes?
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