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New Former Member
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Discussion Starter #1
I have a question about one of my buddys trucks since I dont know much about the duramax, the truck is a stock 02 exept a 4in downpipe back exhaust and the new quadzilla programmer we just put on, ever since we messed with it the truck acts like its running out of fuel at like 50-60 mph then if you stay in it will clear back up and keep going good, one day the truck even cut off and wouldnt start, and it seemed the fuel system lost prime with over half a tank of fuel. We tried unprogramming the truck and it still does it but after the 3rd time it seemed to get better almost going away. I have no idea what it is, we tossed around it might be the lift pump going out or something but dosnt make any sense to only do it at the higher speeds and not all the time. Any help would be apriciated.
 

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Nasty Girl
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580 Posts
Most definately sounds like a lack of fuel. Do you have EFI live or access to a Tech II? If so I would look at the rail pressure at WOT. ;)
 

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New Former Member
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39 Posts
Discussion Starter #4
Most definately sounds like a lack of fuel. Do you have EFI live or access to a Tech II? If so I would look at the rail pressure at WOT. ;)
We used a snapon modis to read rail pressure when it did run rough and it had two pids for it one was DEM rail pres and the other was ACT rail pressure or something to that effect,the DEM stayed the same where it should be and the ACT went down to near nothing when it did it, is there any way to hook up a guage or something to check if its for sure the lift pump not keeping up?
 

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Nasty Girl
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580 Posts
We used a snapon modis to read rail pressure when it did run rough and it had two pids for it one was DEM rail pres and the other was ACT rail pressure or something to that effect,the DEM stayed the same where it should be and the ACT went down to near nothing when it did it, is there any way to hook up a guage or something to check if its for sure the lift pump not keeping up?
You can add a gauge to your supply line. On a stock system you will actually see vaccum instead of pressure. The CP3 has a low pressure side pump on it to supply the CP3 with fuel and actually draws the fuel from the tank.

But in cases where programmers/boxes, EFI live etc. has been added the low pressure pump can not keep up to the fuel demands. Hense we add lift pumps. The lift pump should stay in a positive state at WOT. 5-6 PSI would be sufficient. If not there are a couple options, you can either run a higher GPH pump or install a solenoid to shut off the return at WOT.

In his case just the addition of a lift pump will be sufficient to solve his problem IMO. Hope this helps.

Keith
 
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New Former Member
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Discussion Starter #6
You can add a gauge to your supply line. On a stock system you will actually see vaccum instead of pressure. The CP3 has a low pressure side pump on it to supply the CP3 with fuel and actually draws the fuel from the tank.

But in cases where programmers/boxes, EFI live etc. has been added the low pressure pump can not keep up to the fuel demands. Hense we add lift pumps. The lift pump should stay in a positive state at WOT. 5-6 PSI would be sufficient. If not there are a couple options, you can either run a higher GPH pump or install a solenoid to shut off the return at WOT.

In his case just the addition of a lift pump will be sufficient to solve his problem IMO. Hope this helps.

Keith
Oh I didnt know that about the CP3 pump, I thought they had lift pumps to supply fuel to them, interesting. Well im thinking like you said just adding a lift pump to the system should get rid of the stumbling engine problem.

Thanks for the help nasty girl, I saw your truck in diesel power very nice setup I couldnt imagine 1000hp street truck, congrats on the first 1000hp Duramax too.
 
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Senior Member
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236 Posts
You can add a gauge to your supply line. On a stock system you will actually see vaccum instead of pressure. The CP3 has a low pressure side pump on it to supply the CP3 with fuel and actually draws the fuel from the tank.

But in cases where programmers/boxes, EFI live etc. has been added the low pressure pump can not keep up to the fuel demands. Hense we add lift pumps. The lift pump should stay in a positive state at WOT. 5-6 PSI would be sufficient. If not there are a couple options, you can either run a higher GPH pump or install a solenoid to shut off the return at WOT.

In his case just the addition of a lift pump will be sufficient to solve his problem IMO. Hope this helps.

Keith
Is it just me or is there an echo in here???? lol! :D
 
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