when i was having trouble with mine i had several mech. ask me what the lift pump pressure was at the cp3. why did they ask then. why do we put the low presure gauges on then?

 

Because if you have pressure while running the engine the assumption is you have the required flow. This assumption is normally true but he does not have a gauge to check his pressure while running. So the zero pressure flow test is the best option short of installing a gauge. 100% stock any pressure over zero should meet required fuel flow.

 

The original post is that above 2500rpm the truck falls flat.This is when fuel flow is critical especially in the taller gears.The cp-3 uses the cascade overflow valve to take inlet pump pressure and ramp it to 85lbs+.It has 3 functions,directing fuel to be further pressurized for injection,internal lubrication and return excess.If the inlet volume is not enough to meet this pressure the valve does not direct fuel for injection it simply maintains lubrication and return flow.This why the cp-3 has a much longer life span than say the vp-44,it will not allow the lubrication portion to be cut short.I'm not implying 100% that he has a fuel supply problem but it is the first and most simple thing to check and it is a very common issue with the filter mounted pumps.


Heres some good reading on the cp-3 if your interested.
http://www.cumminsforum.com/forum/3r...mp-system.html

 

true. the flow test is his best option with out installing the gauage.

 

After reading this, it sounds like it could be one of two things: lift pump or FCA. Is FCA failure a common occurrence?

 

you can search the fca on here for some more reading on it.