Hi, I installed an Airtex E8153 pump. I have a 25 gpm, 10-micron spin on fuel filter. between the tank and pump. I also installed a fuel pressure gage in the cab that gets fed off the supply line to the cp3. When I turn the key on I get 10-11 psi after I start it goes to zero then back to 5-6 psi. I was wondering if that is enough fuel supply for the cp3.

The psi is good but remember the CP3 is the CRD's fuel pump so your Airtex is a supplemental pump not the "real" fuel supply pump. I phrase my comment this way because it's not clear that the Airtex is a "flow through" pump. A flow through pump is designed so if it fails fuel can continue to flow through the pump which is obviously an important consideration when installing a supplemental fuel pump.

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Thanks for answering. It is a flow through design. I wired a switch in and can shut the pump off and the jeep will still run.
Would going a little higher in psi and flow do any damage to the cp3?

Sorry for the long answer, but it gets complicated!

*Up to a point, No!
The in-tank installed lift pumps supplies ~12-14 psig to the CP3, so anything under 15 psig is just fine and within the limits of the recommended low side pressure! Any excess pressure/flow that the CP3 does not use is returned to the fuel tank via the fuel return system.
The CP3 has an internal pressure regulator (FCA = Fuel Control Actuator) on the low pressure side that regulates return pressure.
There is such a thing as too high of a pressure that can exceed the return capacity of the internal pressure regulator! When this happens

On the Dodge Cummins that uses the same CP3 fuel injection pump and a 'from the factory' installed in-tank supply pump which is the same one most people are installing in their Jeep CRD tanks; the recommended low side fuel pressure is:
*Dodge CR 5.9L and 6.7L = 8 to 15 psi

(*per Diesel Injection Service Guide to the CP3 injection pump)

The CP3 fuel pump was used in the Dodge Diesels (Cummins Engine) starting in 03 and continued for many years and is the same injection pump as installed in our 05 & 06 Jeep CRDs.
GM Duramax also used the CP3 injection pump for several years as well....

Supplying the CP3

Users should never push fuel to a CP3 at a high pressure. Because it has a built-in supply pump, the CP3 only needs to be supplied at a low pressure and it will handle supplying the pumping chambers from there. Whereas some previous injection pumps had to be somewhat pressurized, the CP3 handles its own pressurization.
... the internal supply pump within the CP3 is a constant displacement gear pump.
Being a constant displacement pump means that it you can't hook just any supply pump up to it. Whereas an injection pump like a P7100 can tolerate a large difference in flow rates to/through it with relatively little pressure change, the CP3 cannot. If you try to push too much fuel to the CP3, the high pressure can skyrocket. There are no internal relief valves in the CP3, only a direct feed to the supply pump. Conversely, if there isn't enough flow to it, the pressure will drop and the supply pump will actually start developing a vacuum in an attempt to get enough fuel to supply its needs.

Conversely, users DO have to worry about getting enough fuel to the CP3. (Reason to install a lift pump) Remember the COFV? It prioritizes the flow and when there isn't enough fuel to the CP3, it shuts off internal lubrication and cooling flow. This is very bad news for the longevity of the CP3. Diesel fuel viscosity and lubricity falls dramatically with an increase in temperature. Hot fuel within the CP3 is bad. (Why some on this forum have installed fuel line return coolers)
Basically, one needs to get enough fuel from the tank to the CP3 inlet at low pressure to keep the CP3 well fed and cooled, yet not over pressurize it doing so.

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