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01-04.5 LB7 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 Ect

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Old 11-27-2012, 07:42 AM   eBay Motors  #1 (permalink)
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long start time

Hi There-2003 Duramax 6.6-243,000kms-turns over for 10-15 seconds before starting-if it does at all-sometimes takes so long it has to be boosted and prime the filter at the same time to get going.

Dealer told me it was the sensor in the tank-paid 800.00 for it and changed it to no avail.

Dealer says nothing shows on the monitor he plugged in.

No diesel leaks anywhere-new fuel filter.

Important history note-first time dealer gave me the sensor part it was wrong-for a gas motor-so I put the whole thing back together with the old parts-sensor- and it worked beautiful for 3 days-started fast-real fast. Then I filled it up-right to the lid-and right there at the pumps it wouldn't start again? Thats when I went and put the right part in-to no avail.

Now at another dealer who doesnt know either but wants to start tearing it apart. Any suggestione before I let that happen?

Thank you.Mike
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Old 11-27-2012, 08:37 AM   eBay Motors  #2 (permalink)
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Is it holding a prime when you prime the filter? Does it get hard in a few pumps?
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Old 11-27-2012, 09:39 AM   eBay Motors  #3 (permalink)
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mine started doing the same thing around 240k, new cp3 and never had a problem since.. pump was just getting week, 3000 psi under des pressure at an idle, not good.. maybe check yur actual and des fuel press with a tech II...
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suncoast stage 4 trans, goerend "ML style" triple disc billet converter
Passin' 35psi on stock IHI with 290k on it
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Old 11-27-2012, 10:14 AM   eBay Motors  #4 (permalink)
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Could be the filter head needing rebuilt. They can let air in which will cause the truck to lose prime.

If it takes more than a pump or two to get the primer pump hard then that's probably the problem. Easy and cheap fix too.

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Old 11-27-2012, 01:33 PM   eBay Motors  #5 (permalink)
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long start time

Hi Guys-cant get this page to show your replies while responding so hope I get everything answered
1/ takes many many pumps to get primer hard
2/sorry what is a cp3?
3/ had pressure checked and it's good
4/ just changed the fuel filter again and still the same

Hope this helps

Thank you.Mike
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Old 11-27-2012, 01:43 PM   eBay Motors  #6 (permalink)
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a cp3 is the fuel pump..gr8shot might hav had a good idea going there.. that would explain it losing prime and having to pump n pump for prime...i guess im tapped out of ideas at the moment... my buddies lb7 wont start after its warm but fires right up when cold..and i dont why and neither does he..
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Eddie "boost master"
03 lb7 ccsb 4x4 inch lower than stock 20" mkw's 305/50/20 cooper zeons
auto meter boost/pyro/trans gauges- traction bars- 5'' DE 5" to 7" black mitre cut stack- PPE BIV- AD II 200 lift pump- edge insight CTS- spectre CAI- 45% over injectors- LMM cp3 & FPR -EFI live dsp5 from tony burkhard and danville performance
suncoast stage 4 trans, goerend "ML style" triple disc billet converter
Passin' 35psi on stock IHI with 290k on it
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Old 11-27-2012, 05:41 PM   eBay Motors  #7 (permalink)
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The in tank unit is only a fuel gauge sender and a tube for fuel pick-up.

The system uses the injection pump [CP3] to pull the fuel from the fuel tank, through the filter and FICM. Any small leak will allow the pump to suck air, and little fuel. The Filter head seals are cheap from a supporting vendor [GM does not service the seals] and easy to replace. Good place for any one to start when haveing a starting problem.

The LB7 engine -[01-04] has had some injector problems, and one is excessive leaking/passing fuel by the inter seals. That can cause hard starting when warm, but starts OK when cold, because the fuel is more dense when cool. The engine needs around 5,000 psi to start. A injector return test will show if you have a injector problem.
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Last edited by jc1843; 11-29-2012 at 07:07 AM.
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Old 11-27-2012, 05:54 PM   eBay Motors  #8 (permalink)
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Moving to LB7- truck runs
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Old 11-28-2012, 05:16 AM   eBay Motors  #9 (permalink)
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OK-will now go change the filter head seal and see if that works.

Thanks again guys-appreciate the help.Mike
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Old 11-28-2012, 03:49 PM   eBay Motors  #10 (permalink)
 
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My 2006 LBZ Duramax is doing the same thing. After I crank it forever it fires and runs fine. I originally thought it was the glow plugs not heating. But the mechanics have said the glow plugs are working fine.


Its at the shop right now and the mechanics are puzzled. They've got an 2005 LLY doing the same thing. They've replaced the high pressure fuel pump, and the fuel filter housing and it didn't do anything. They're now replacing injectors on that truck. I'm glad they haven't started pulling mine apart...

Im going to try a couple of things y'all have mentioned. I hope I figure out something.
Please let me know if you find a solution. Thanks Zack.
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