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Hey Duramax Experts

Discussion in 'Trucks' started by Luvnlife, Dec 28, 2018.

  1. Luvnlife

    Luvnlife Head Ram Rod

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    2003 LB7. All stock. Hard cold starting, hot starts are fine. If I plug it in it usually starts fine but really shouldn’t even have to plug it in, the temp is like 30. Hook my scanner to it and rail pressure before start up is 178. When it starts rail pressure at idle is just above 5000. I can watch it as I start it and it’s not building rail pressure above 1000, truck doesn’t start unless it builds to above 1200, computer controlled. I just replaced all the fuel hoses on the engine as they were pretty bad but didn’t replace the braided ones. Pumped air into the tank but didn’t see any fuel dripping. New filter head and filter. Balances were checked about six months ago and all within spec but I can’t remember if the tech checked return rates. What do you think?


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  2. yz450mm

    yz450mm Well-Known Member

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    Weak batteries? Or one bad battery drawing down the other?

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  3. Luvnlife

    Luvnlife Head Ram Rod

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    I load tested them and they checked out but it’s always a possibility. Voltage drops can fuck with you. But I’ve been having this problem for almost a year so if that was it you would have thought the batteries would have taken a shit by now.


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  4. yz450mm

    yz450mm Well-Known Member

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    If one cell in one of the batteries is going bad then it can really suck down a lot of juice when you try to start, but the rest of the time the rest of the cells might be able to compensate.

    If your batteries are getting older then it definitely wouldn't hurt to throw some new ones in there anyways, might just solve your problem the easy way.

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  5. Xring01

    Xring01 Well-Known Member

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    One thing you should consider.....

    I had to replace the "Priming Pump" the seals in mine failed, started to leak air a bit, not fuel... not alot, just enough that it would lose prime every month or so.... We would have to prime it, to get it to start.

    I have a feeling that your fuel system is sucking a bit of air, and the priming pump could be the culprit...

    Mine is a 2002 LB7...

    Hope that helps.
     
  6. Luvnlife

    Luvnlife Head Ram Rod

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  7. Luvnlife

    Luvnlife Head Ram Rod

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    Has a new filter head. I got in a bind and had to take it to the stealership. Now I know there is a rebuild kit. Anyway that was the first thing that got done, new filter head and filter. I myself believe I might be sucking a little air. Like I said I replaced all the rubber lines which they were all in bad shape. I didn’t replace the braided ones but I put air to the tank and I didn’t see any fuel even up on the rails.


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  8. Xring01

    Xring01 Well-Known Member

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    While we are on the subject of Duramax/Maintenance..

    Mine is 2002 LB7, and I have had to replace a couple of the Power Steering hoses... Dried out and started leaking... Power Steering also interties with the Brake system... I think I will have to replace another hose soon... I have a very very small leak, that I havent found yet...

    Once the leak gets a bit bigger, I should be able to find it, and fix it..

    The reason why I am bring it up... While you are in there servicing the thing.. something you might want to have inspected/replaced while you in there...

    Let me know what was wrong with yours... when you finally figure it out..

    Overall, I have very happy with my truck.. I paid $17,500 for is 10 years ago ish... Bought it used with 105,000 miles, and currently has 192,000... Just a few minor things that we have had to do, rebuilding the priming pump, and a few hoses... Runs great... gets the job done...

    Hell a buddy of mine borrowed it the other day to tow a Bull Dozer from San Diego to AZ... he loved my truck and tried to buy it from me... I get offers for it, just about everytime I get more fuel.. lol...

    Great Trucks and I have gotten my $$$ worth out it, especially when you look at the price of the new/used ones out there.. wow.
     

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