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Duramax 6600 Welcome to the Internet's first Duramax 6600 diesel discussion forum for the LB7, LLY, LBZ, LMM, LML, LGH & L5P RPO code engines. Tips on performance, fuel economy, troubleshooting and more.

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  #21  
Old 04-19-2010, 01:49 PM
Kennedy Kennedy is offline
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Mark,

I can't really say definitively, but in talking to my sources my gut is saying that you are seeing the injectors begin to fail in the ball seat area. This causes excess return rates and of course high fuel temps. I'm hearing more and more of this same complaint with the LBZ these days, but have yet to see one through to the end.

The big thing I am interested in is seeing a set of used injectors from a vehicle exhibiting these symptoms. Then we could test and look at whether it's an abrasive wear issue or a cavitation issue.

I have a notion it's time for another round of me harping: FILTRATION, LIFT PUMP, ADDITIVE...
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2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
2005 Chev K3500SRW D/A CC Long LT(SOLD)
2007 Chev K2500 Classic EC Short LT (Sold)
2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
2016 GMC K3500SRW D/A CC short LTZ

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Last edited by Kennedy; 04-19-2010 at 04:36 PM.
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  #22  
Old 04-19-2010, 02:06 PM
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Mark Rinker Mark Rinker is offline
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"Gawd, with all this driving I've been doing - I hope I don't fail in the ball/seat area as well..."

JK - I switched to your tune earlier today. Going to run it for the next 5K miles at least, for the boats and destinations listed above. The next two boats are on their own trailers, with ~500 miles of empty truck/no trailer inbetween. Should be able to get a good read of unloaded cruising mileage at 65mph average.

I am starting to prepare myself for the reality that I will be buying and installing my first set of injectors for cash. Hopefully I can get through the spring push, first - and spend the money from savings, rather than throwing it on the AMEX and paying it off over the next few months. Its NEVER in the budget...
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  • Total GM diesel miles to date : ~950K
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  #23  
Old 04-21-2010, 09:20 AM
Kennedy Kennedy is offline
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I don't know if you plan any vacation/down time, but if you do we could try to pick a pair of suspect injectors and have them tested. They'll be the hottest of the bunch. Not sure how well a guy could test with a IR thermometer if some similar device, but this should help narrow down to the worst offender(s)
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More than just a salesman-I use and test the products that I sell on a daily basis!
Superflow Lie Detector in house
2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
2005 Chev K3500SRW D/A CC Long LT(SOLD)
2007 Chev K2500 Classic EC Short LT (Sold)
2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
2016 GMC K3500SRW D/A CC short LTZ

Custom tuning in house using EFI Live tuning software!
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  #24  
Old 04-21-2010, 01:28 PM
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A fuel pressure/vacuum gauge, like the one JK sells, would tell you in moments what the suction draw is, which is an indication of fuel filter life or if a problem might be with the fuel supply system (plugged sock in tank, crimped hose, etc.).

Jim
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  #25  
Old 04-23-2010, 09:11 AM
Kennedy Kennedy is offline
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Quote:
Originally Posted by More Power View Post
A fuel pressure/vacuum gauge, like the one JK sells, would tell you in moments what the suction draw is, which is an indication of fuel filter life or if a problem might be with the fuel supply system (plugged sock in tank, crimped hose, etc.).

Jim
I've done everything but hit him upside the head with the gauge so far and he still hasn't grasped the value when troubleshooting OR knowing when it's time to replace that expensive fuel filter.
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Kennedy Diesel-owner
More than just a salesman-I use and test the products that I sell on a daily basis!
Superflow Lie Detector in house
2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
2005 Chev K3500SRW D/A CC Long LT(SOLD)
2007 Chev K2500 Classic EC Short LT (Sold)
2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
2016 GMC K3500SRW D/A CC short LTZ

Custom tuning in house using EFI Live tuning software!
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  #26  
Old 04-23-2010, 11:47 AM
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LOL - however I don't see anything that points to a fuel system restriction, as that would be a more consistant problem.

What I am describing / experiencing happens only under very specific circumstances - i.e. heavy load + pulling hills + outside temps >75F.

Its definately fuel temp related, unless 180-190F fuel temps are considered normal...
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  • Total GM diesel miles to date : ~950K

Last edited by Mark Rinker; 04-23-2010 at 12:01 PM.
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  #27  
Old 04-24-2010, 07:39 AM
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Quote:
Originally Posted by Mark Rinker View Post
Its definately fuel temp related, unless 180-190F fuel temps are considered normal...
Or you can't get enough fuel through the system to control the temps...

Whack!
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  #28  
Old 04-24-2010, 09:52 AM
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Quote:
Originally Posted by Mark Rinker View Post
LOL - however I don't see anything that points to a fuel system restriction, as that would be a more consistant problem.

What I am describing / experiencing happens only under very specific circumstances - i.e. heavy load + pulling hills + outside temps >75F.

Its definately fuel temp related, unless 180-190F fuel temps are considered normal...
Realistically, no. It isn't. You're talking to the wrong end of the horse. Cause <-> Effect. Your fuel temp is an effect, not the cause. It isn't a paradox. Something is causing the results you are seeing. Elevated fuel temperature is the result of a component failure.

180-190°F is not normal. On mine (2001, but it shouldn't be too far off), the highest temp I've seen is around 160°. That was ascending Pacheco Pass (several miles of 6%) with 22K+ on, and an ambient temp of 118°F. It was as hot as it was going to get.
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  #29  
Old 04-25-2010, 05:34 AM
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Guys, I clearly understand that the fuel is getting too hot, as a result of SOMETHING. Certainly the fuel is getting its heat transferred from engine componants - injectors and/or injection pump, its not pumped into the truck HOT! LOL

Yesterday was a big heavy boat up the North Shore of Lake Superior. All the ingredients for setting a code - except one - ambient temps were in the 40s and 50s, so no issues and fuel temps were 130s-140s, max.

Load + outside heat + hills = high fuel temps, in my case. When it hits 180/190...BING! I get the code.
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2011 Chevrolet Tahoe 5.3L daily driver
  • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
  • Total GM diesel miles to date : ~950K

Last edited by Mark Rinker; 04-25-2010 at 05:59 AM.
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  #30  
Old 04-25-2010, 05:37 AM
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Quote:
Originally Posted by JohnC View Post
Or you can't get enough fuel through the system to control the temps...

Whack!
If I were short on fuel, I'd be short on power. Power is normal - even when turned up with JK's tune. Yesterday on a few hills, I downshifted to 4th and stood on it. My pump can maintain 24k requested and 24k actual fuel rail pressures, indefinately. Try that with a plugged/plugging filter, crimped fuel delivery hose, or plugged tank sock.

Sure looks like injectors to me, but I won't be replacing them until there are more driveability related problems than I am experiencing right now. Todays issue is the ECMs, and a theoretical one for members of TDP to digest. (No white smoke, no power loss, no knock, no oil dilution, etc...)

I am not concerned, under extreme circumstances, that my Requested and Actual FRP vary by >10%. In fact, this whole issue could be programmatically eliminated through a few tweaks with EFI-Live...there are probably many LB7 trucks out there running around with the same issue, but the ECM doesn't detect the variance and set a code. That is why an LB7 with restricted fuel filter will run until power is down, with no check engine light. LBZs with same filter restrictions will complain of low FRP...
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2011 Chevrolet Tahoe 5.3L daily driver
  • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
  • Total GM diesel miles to date : ~950K

Last edited by Mark Rinker; 04-25-2010 at 06:11 AM.
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