Duramax Diesels Forum Truck of the Week
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Old 06-17-2015, 06:47 PM
Adoom01 Adoom01 is offline
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Default Losing fuel prime when it's hot

2002 silverado 2500hd lb7
when I bought it a year ago I put new injectors a and glow plugs in it because it needed then which it didn't fix the losing fuel prime when it's hot I have rebuilt the fuel filter head and put in a fuel pressure relief plug which still hasn't fixed the problem it starts fine when it's cold but when its at normal temperature u can't start it again it looses fuel prime it even runs fine no looping it stalling at all lacks on power a bit because it's getting at in from some where

Any ideas???
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Old 06-17-2015, 07:14 PM
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Check the rubber lines that connect the hard lines to engine on drivers side by firewall. They sometimes get soft from the heat and suck together. Also make sure your fuel cap is venting
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Old 06-17-2015, 08:24 PM
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If u pump the priming bulb when its hot will it start? Or do u have to let it cool off?
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Old 06-17-2015, 08:29 PM
Ron Nielson Ron Nielson is offline
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If replacing the fuel lines doesn't solve the problem, buy a completely new fuel head. This comes with new fuel filter and WIF also. Cost is in the neighborhood of $125 US.

If that doesn't solve the problem, install a lift pump, either a nice pre-engineered unit or even a home-built model, with a filter between the tank and the pump. (You want that new pump receiving only clean filtered fuel to send on to the engine.) I used an Airtex E8153 pump and a NAPA 4770 filter base, simple shut off valve to control spillage when changing filters. Has worked great since 2009.
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Old 06-17-2015, 08:55 PM
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Lift pump and remove the stock filter.

You can pressurize the fuel tank and look for leaks

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Old 06-17-2015, 09:05 PM
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I have this same issue on my 2001, and only in the heat. Most of the year here in Idaho it runs fine, but in the few summer months it starts too have issues. Takes longer to start, loping at idle, revving on it's own, etc. but give it any throttle it acts normal. Seems to be worst when i leave it sit in the sun for a few days, or after i take it on long drives. I rebuilt my fuel filter housing and took out the check ball when i got my nicktane and cat filter. In the process of removing it i accidentally cut the lines, so i replaced those too, they looked pretty rough so I'm glad i did. Nothing helped, so I bought a used 6.5 lift pump for $30 that I'm going to try and throw on there, we'll see if that helps..
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Old 06-17-2015, 09:08 PM
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Quote:
Originally Posted by Awenta View Post
Lift pump and remove the stock filter.

You can pressurize the fuel tank and look for leaks

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How do you go about pressurizing the tank? air compressor and a rag?
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Old 06-17-2015, 09:35 PM
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Old fuel cap. Ventless or seal the vent. I think old ford caps work. Drill a hole through it and insert a standard fill valve.

You can use a compressor or a hand pump. Turn the regulator down on the compressor. Pump it to 15 pounds or so. Don't want to spring new leaks. Now wait and look around, the prime pump should be hard too.

I suggest looking around ficm to make sure it isn't leaking there too.

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Old 06-17-2015, 10:08 PM
Adoom01 Adoom01 is offline
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I just let it cool off
or I will spray brake kleen in the breather tube and it will start
other then the starting problem it runs fine
I will check the fuel lines first I did notice that when I pulled the lines off the fuel filter head they came off way to easy with little effort
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Old 06-18-2015, 01:10 AM
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I no u put injectors in but that sounds like high return rates. Usually an air leak won't go away with just letting it cool it would need to be primed. Also the fact that a it will fire up with a shot of brakekleen would also lend to that cause usually that isn't enough to overcome an air leak.
( word of caution. be VERY careful with the starting fluids)
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daily driver: 04 regular cab short bed LB7 to LLY swap and shortened. Normal mods and tuning by me

03 2500 Burb: LBZ swapped!

00 VW beetle TDI: Wifes car 45 MPG
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