Can someone explain to me how our CP3 works?

SIKDMAX

Highway Burnouts!
Sep 14, 2007
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I was thinking... now that I have my liftpump which comes on with igntiion, AKA on when key is in run but truck not started - how does our CP3 return work?

I have my key on often for radio or whatever but engine not running - that means Im pushing 12 psi or so of fuel to my CP3 but the engine is not consuming it. Does the pump need to be spinning for the return line to work, or is the fuel my airdog is pushing being returned to the tank like normal, or am I pushing 12psi to the CP3 and it has no where to go so its backing up and building pressure in the lines or......?

Hope that makes sense
 

super diesel

<<<< Under Pressure
The fuel can push through the return to some degree. It does have some 1 way check valves that are spring loaded so there will be some residual line pressure build. I would install a in cab switch to turn the pump off when just sitting there with the ignition on and engine not running. A switch for the ground or positive power will work. You can also install a pressure switch to activate it by slight boost pressure or oil pressure.
 

JoshH

Daggum farm truck
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Feb 14, 2007
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Why not turn your truck to Acc instead of Ign so it doesn't turn the pump on but you still get power to the radio, or do you have your pumps wired to come on in Acc?
 

SIKDMAX

Highway Burnouts!
Sep 14, 2007
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They come on at ignition but for example at the track friday night it was 85 degrees and just sittin in my truck, so I would have liked to have the fan blowing a bit.... didnt want my lift pump on for an hour though.

Ill wire up a kill switch inside. Thanks guys
 

ZeroGravity58

Well-known member
Mar 23, 2008
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you can probally get the TTS/Kennedy wiring kit and use it for your pump. My pumps will run for 10 seconds i think then you turn the key on then they cut off until you have oil pressure.
 

mde

fuel injection is my life
Mar 17, 2007
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in the CP3 is a bypass valve which sends your overflow back to the tank, when you let run the lift pump, you have a nice circulaction of your fuel and you filter your fuel a few times. :D

V :alc:
 

LarryJewell

Back with his honey :)
Jan 21, 2007
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The fuel can push through the return to some degree. It does have some 1 way check valves that are spring loaded so there will be some residual line pressure build. I would install a in cab switch to turn the pump off when just sitting there with the ignition on and engine not running. A switch for the ground or positive power will work. You can also install a pressure switch to activate it by slight boost pressure or oil pressure.
I have a switch on the ground wire :D