LB7 stalls when cold.. Please help - Chevy and GMC Duramax Diesel Forum
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 03-26-2011, 02:06 PM   eBay Motors  #1 (permalink)
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LB7 stalls when cold.. Please help

Ive got an 04 LB7. The problem is on cold mornings (20's-30's) ill go out to start my truck and ill let the glow plugs cycle then it will fire right up run for 10-15 seconds and run itself out of fuel. once it does this you can crank till you run the batteries dead it will not fire, the only way itll start up once it quits is you push the primer pump 5-6 times till its hard then it will fire right up and run great the rest of the day no matter how many times you shut it off and re-start it. and its not an everyday thing. It might happen two mornings in a row, or it might be fine for a week. At first i thought it may me the cp3 pump going, but i got thinking if that was the case the thing would run like shit and have that problem all the time. So now i think its the Fuel pressure regulator. Im not fimilar with the duramax's bc they never break down haha, now powerstrokes on the other hand im great with.. I was wondering anyone had ever heard of this or had run into this or may have some suggestions since ive read changing the fuel pressure regualtor isnt an easy task.. now ive also got a check engine light on but thats bc my #8 glow plug is bad and has been for over a year, just been too lazy to change it and it starts great anyways. any help would be greatly appreciated thank you
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Old 03-26-2011, 04:06 PM   eBay Motors  #2 (permalink)
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Ever plug it in a night? Sounds like your loosing prime somewhere. Check your fuel filter and filter housing. Two places where a leak could be due to o-ring failing.
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Old 03-26-2011, 04:10 PM   eBay Motors  #3 (permalink)
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You could have a air leak in your fuel line from your tank so after sitting a while your fuel drains back into your tank and you lose prime. Once you get it started you probably dont have this issue because it doesnt sit long enough to lose prime. Im thinking the cold has nothing to do with it.
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Old 03-28-2011, 03:38 AM   eBay Motors  #4 (permalink)
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if i had an air leak wouldnt i also have a fuel leak as well? it wierd, the truck sat most of the week and friday it fired right up with no problem
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04 LB7
33/12.50 17 mickey thompson mtz
edge w/ attitude
intake mod
halo headlights and parking lights
led cab lights
4 inch turbo back strait pipe with 7" tip
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Old 03-28-2011, 04:56 AM   eBay Motors  #5 (permalink)
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I had the same exact problem with my 03 lb7 and everyone said it was either a hole in my lines or my fuel pressure regulator. But i went ang put an airdog lift pump on there and it never did it again. Im in alaska so its almost always cold and its been 6 months now without a problem
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Old 03-28-2011, 09:56 AM   eBay Motors  #6 (permalink)
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Unless you have a lift pump, the fuel isn't under any pressure until after the cp3. The cp3 creates suction which pulls the fuel from the tank to the engine. A small leak on the suction side would not leak fuel out, but could very well allow air into the system.

I was having this problem for awhile. I could drive for two or three days without an issue, and then it just wouldn't start. Priming would correct the problem. I traced it to a leaky bleeder screw o-ring. I had already ordered a replacement aluminum screw, that hadn't arrived yet, so I took the old o-ring off and found a suitable replacement at a local auto parts store. That solved the problem until my shiny new replacement screw showed up.
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