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Fummins

Ideal fuel pressure

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I have the original Airdog 100 on my truck feeding my CP3 (with Arson III kit). I only see about 8 psi on my guage. I'm new to Cummins engines and am not sure the ideal pressure for the CP3..

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With a modified CP3, 8psi is probably too little lift pump pressure......especially with a heavy foot. If you're looking to replace the AD, I'd have to say to get the Raptor system. High quality, built in pressure regulator (no return fuel line) and easy install. IIRC, if you're still running the factory fuel filter housing with the plastic cap, you can run up to about 60psi before the plastic cap cracks. Most guys run from 18-40psi. Some of them have LP systems that increase LP psi as the engine rpms increase. Mine usually is about 25-27psi depending on fuel temperature.

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I was going to try changing out the spring on my AD to see if I can get it up to abouy 15-20 psi.

--- Update to the previous post...

I changed out the spring in my AirDog.. Pressure is now 23-25 psi and it seems happier, although I didn't have a chance to "get on it".

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Bosch specs are -5 to +15 psi, but that's for an all stock pump. I would call Wicked and see what they want since you have modified your pump. Flow is much more important for a CP3 than pressure. But I think the most common psi is about 15-16 at idle.

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Flow is much more important for a CP3 than pressure. But I think the most common psi is about 15-16 at idle.

You are so right!!!! So many folks.........usually CF types..........don't understand that!!! Pressure often gets confused with volume. Flow can also be stated as "volume of fuel available". The CP3 can only take in "X" amount of fuel. Period!!!! What it doesn't need for injection goes into cooling itself and for self-lubrication and then goes back to the tank. The CP3 will pull fuel on it's own........don't ask how I know!!!!! But in heavy fueling needs (heavy, uphill towing, sled pulling, etc.), it can't draw enough to fuel and provide cooling at the same time. So that's why we use a lift pump...........to provide more than enough fuel for our work needs and more than enough for CP3 cooling and lube needs.

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I have a STOCK '05 2500 4x4.

I am thinking of getting a smarty, edge etc. for moderate HP/tq bump on a daily driver (and have lurked here researching those).

From day one, my fuel pressure dipped below 5 psi and the low pressure idiot light I installed would flicker under moderate to hard acceleration.

I double checked it with a guage, and sure enough it dips to 3.5-4 psi.

Another forum said not to worry about it.

If I'm to upgrade with a smarty, edge, should I upgrade the pump in the tank first? If so, with what?

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Your experience is why I think lights are a waste of $$$$ on a CR. 2 psi is the lowest you want to see WOT. I would get a gauge and a Smarty, along with a big line kit and hi-flow inlet banjo and see where you are. At +100hp at 3 fuel filters I don't get below about 4psi WOT, but have a big-line kit and no stock banjos.

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