The bosch cp4 piezeo fuel system found on the 6.7 requires return pressure.
The pizeo crystals used to open the valve inside the injector are not strong enough to properly operate the valve. The valve is the little silver pill that is under the fuel plates. Then high pressure fuel goes down through a tiny hole (maybe restrictive hole
) in the fuel plate and lifts the needle off the taper seat allowing the nozzle to spray.
The best advice I could give you is to always be sure to supply the proper fuel pressure to the injectors and hpfp.
Cp4 needs 65 (120) max
Cp3 requires 10-15 (over 15 has been proven to cause damage in other applications)
Injectors require up to 150 psi of return pressure.
I chose to run my second cp3 and others I have installed with a seperate fass system using a seperate pickup and return. This was the only way I could meet all manufacturers requirements and assure a successful result.
There are also some systems from a fellow named 2 micron. He has added filtration for the common rail vdubs. They have a cp4.1 single piston which has a history of failure. But basically the same system as ours.
I actually use the ford cp4 to add fuel volumn on tuned vdubs. If you change cams and spacer plates the ford pump is direct bolt on. You just need to run a line from the extra cylinder to the rail. Dual fueled 2 liter tdi
You also have the option to switch to a gm duramax lml cp4. That pump includes a gerator pump on the back, has barb fitting inlet and outlet, and can be supplied at 15 psi fuel.
Almost all the new diesels are very simalar.
I hope this answers the question.
