Way TOO HIGH! Can cause catastrophic problems with the CP3!
Here is why from an earlier post:
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 (high pressure) to the CP3, the high pressure discharge 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.
