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How much pressure is too much for the CP3??

675 Views 5 Replies 3 Participants Last post by  steved
Just what it says, how much is too FASS is sitting around 25psi...truck runs great.

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then why change anything :D:
It is one of those things...I can lower the pressure of the FASS by changing a spring..if it will increase the longevity of the CP3, then that is a worthwhile mod.

Just because the truck runs good doesn't mean something isn't getting damaged.

Changed to a 13 psi spring...everything is back to normal now...12 psi all the time.

you want volume to the CP3. Some on the TDR were seeing high pressure to the CP3 and low volume so it was sacrificing HP on the dyno. i haven't had a chance to hook my fuel pressure gauge up yet but when on the dyno the DRB said the engine requested 26k rail pressure and it dropped to 13k when wide open. All the 3rd gen's were dropping rail pressure with one having a bad pressure relief and never able to build more than 11k. Mine went back to 26k when coming back out of the throttle. i put down 491 HP
Yeah, I know all about the pressure/volume main concern (in my setup) was the FASS over-pressuring something like a seal...I also was reading Tomeyguns findings about the fuel rail relief valve issue...since I'm not modified, that shouldn't be a concern.

I know too little volume is bad, but at the same time volume and pressure are sorta the same...I guess it also depends on where you take your pressure readings at could be seeing "good" pressure upstream near the pump and low pressure (and volume) downstream because of inline restrictions (ie small lines, restrictive banjo fittings, plugged filter, etc.). I think the general concensus is that the factory fuel system is just barely adequate, but to get the optimum fuel build/buy your own!

With this 13psi spring, I got 12psi. I took the truck for a test "run" and basically did several 100mph "onramp" traffic merges in 5th and 6th (these were also upgrade pulls)...I also have a low pressure light in the cab (the gauge is out next to the CP3, the light's sender is on the pump) never flickered so I can a$$ume that the pressure isn't dropping to 7psi...and that should provide plenty of fuel (through a 3/8" hose) to the CP3 hopefully.

It still runs better than it did with the factory fuel delivery system!

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