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Discussion Starter #1
Been doing some thinking and trying to clear something up in my head. I know the old vp44 pump its important to monitor fuel pressure so you don't kill the IP. Why is this not so important on the cp3? Also what should the pressure be on the common rail trucks? I am still trying to figure whats wrong with my truck. I don't know enough about this motor to figure it out and can't afford to pay someone to look at it or just start throwing parts at it.
 

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mine runs about 7500 at idle and can get up to 28K
This is measured with the bully so I dont know how accurate it is but at least its relative so I can use it for trouble shooting when necessary
hope this helps
 

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Been doing some thinking and trying to clear something up in my head. I know the old vp44 pump its important to monitor fuel pressure so you don't kill the IP. Why is this not so important on the cp3? Also what should the pressure be on the common rail trucks? I am still trying to figure whats wrong with my truck. I don't know enough about this motor to figure it out and can't afford to pay someone to look at it or just start throwing parts at it.
LP pressure from the stock pump should be around 8/12#, rail pressure anywhere from 5k to 24k stock.

What are the symptoms you are experiencing? What makes you think something is wrong?
 

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The stock lift pump on my 03 ran 7# at idle. The replacement intank pump ran 10# at idle. With my TST turned up, I could pull the origional one down to 0#.
It would be a good idea to get it checked to know what kind of pressure you have.

Randy
 

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my cp3 maintains 8psi at idle and will drop to 5psi at WOT.
 

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Discussion Starter #6
Well when I bought it about a month ago, I was getting about 16 mpg and it any gear when I hit the pedal it would put ya in the seat a little and take off. Now I am down to about 13 mpg and it just doesn't feel like its making any power. I thought that it might be a boost leak but I can't find one. Its also smoking a light grey haze and it wasn't doing that before either.
 

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the CP3 is a more sturdy unit over the VP44. yes it still uses diesel to cool and lubricate, it just doesnt need as much to do the job.

idle you should see 8-10psi off the lift pump. running down the road should be 4-6psi, at wide open throttle as long as you have some pressure your ok. now the rail pressure is a different story. . .the rail itself should have about 5K at idle, 12-16K normal cruise, and at wide open throttle you should see it rise to as much as 22K but level out around 20K.

when was the last time you changed the fuel filter????
 

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My GDP Walbro lift pump system gives me 25-26psi with warm fuel. That's pre filter reading and going through 2 fuel filters....a 7micron in the stock canister and a GDP 2 micron plumbed in after that.:hyper:
 

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Well when I bought it about a month ago, I was getting about 16 mpg and it any gear when I hit the pedal it would put ya in the seat a little and take off. Now I am down to about 13 mpg and it just doesn't feel like its making any power. I thought that it might be a boost leak but I can't find one. Its also smoking a light grey haze and it wasn't doing that before either.
I would double check my air intake, make sure the filter hasn't collapsed or something was left in the tube(rag). Also what Drew said(fuel filter), but with the gray haze I would lean towards intake.

Keep an eye on your oil level, if you have an injector sticking, it will start filling your crankcase with fuel, hope that is not the case, but with the poor mileage and haze, I'm just throwing ideas out there that you can check without it costing you anything.

If you had a weak rail relief valve, that would also rob you of mileage and power. To check it, remove the banjo bolt from the top of the valve, gently bend the fuel line away from the top of the valve, look into the valve, should be dry. Start the truck, hold a rag over the top of the valve and have someone run up the rpms to increase rail pressure, it should not leak, if it does you found your problem. I did not use a rag and fuel blew all over the underside of my hood.

Hope this helps, Jess
 

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Discussion Starter #10
fuel filter is brand new. Air filter has about 2000 miles on it and its not colapsed. I haven't checked the oil in about a week so I will check that tomorrow. I will also do the rail pressure thing. How high do you run up the revs? Just a little over idle or what?
 

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the CP3 is a more sturdy unit over the VP44. yes it still uses diesel to cool and lubricate, it just doesnt need as much to do the job.

idle you should see 8-10psi off the lift pump. running down the road should be 4-6psi, at wide open throttle as long as you have some pressure your ok. now the rail pressure is a different story. . .the rail itself should have about 5K at idle, 12-16K normal cruise, and at wide open throttle you should see it rise to as much as 22K but level out around 20K.

when was the last time you changed the fuel filter????
How can I test the pressure of mine
2007 5.9 haze and slightly rough idle New reman injectors and new fuel filter
Just started this weekend only dose it sometimes about 75% of the time
 

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This is 12 years old.
Carl please start a new thread with you exact post

go to 3rd Gen. Powertrain and click "Start Discussion"
 

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also has some bad information in it lol...
 
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