skydiver41

Greetings all. I've hot rodded many a gas powered street racer and now need to better understand these diesels. How about some fuel system basics. My 2006 has in "in-tank" electric fuel pump called a ??? It should on a stock engine, make about 7.5 to 9 psi at idle and 3 to 5 psi at WOT, correct? The in-tank fuel pump pumps fuel through the canister type filter/water separator, then to a much higher pressure pump (electric or mechanical?) called a ??? that feeds the common rail and then on to the injectors...is this correct? This fuel system will prove to be inadequet when I bump the HP (with something like a Quad box) up to +65 hp or is it +100 hp. Thanks in advance.

bigwheels94

The first pump in the system is called the LIFT PUMP.It's sole purpose in life is to supply fuel to the High pressure pump,called the CP-3.It provides the 25,000psi that fires the fuel injectors.I did some research with the cummins spec sheet,& they call for 11 psi fuel pressure @ full load.(WOT) it must flow 50 gph,& maintain that pressure to the CP-3.I'm changing mine asap,even thoe I haven't addad any fueling box (yet.)I recomend everyone do the same.

skydiver41

Thanks for the info. Where did you find that Cummins Spec Sheet? I've got a fuel pressure gauge on the way from Geno's and will be installing it as soon as it arrives so I can start monitoring it's performance.

The Boss Hog

There is an additional, intermediate pump located between those two. It bumps the pressure up to 80 - 180 psi.

The Boss Hog

HOHN

Your HPCR fuel system is mechanical, but has a number of electronic controls. The CP3 and the intermediate pressure pump are driven off the engine's gear train (all CTDs are factory with gear drives-- no timing chains or belts!)

The common rail can provide UP to 32000+psi, but it's not operating at that level all the time.

The fuel injectors are unlike any previous CTDs in that they are opened and closed by direct electronic actuation-- not just pressurized fuel. In the old days, the injection pump was king, as it was the brain of the engine-- like a carb and distributor rolled into one.

But now with the HPCR, the crucial engine management functions are moved to the injector. The HPCR just provides presurized fuel to a common rail. It doesn't have to do much "thinking" like older CTD injection pumps did.

As for adequacy, the fuel delivery system is barely passable for stock, imo, and needs upgrading to live happily with more HP.

Feel free to pm if you have more q's.


Justin

bigwheels94

I'm a Cummins Dealer/Technition.I have access to info through other channels.The specs,I quoted are actually for the Industrial QSB-325 engine.They're allmost exactly the same.