hey, my edge juice (well actually attitue\de) says on hard acceleration i can get my fuel psi to drop to 4psi. idle its at 13

 

sounds ok. . .whats your cruising pressure.

 

Mine too. My idle is around 12 but gets down to 4 on hard accel. My crusing is between 9 and 10.

 

Be careful. These trucks are prone to have a faulty lift pump. I wouldn't be comfortable with 4psi. it is probably okay but less than this could cause damage to your injection pump, which is very expensive. After my 2nd lift pump failed I installed a FASS system, now I run above 15 psi even at WOT.

 

with the stock lift pump, as long as you have over 4 psi at full throttle you are ok. it is just when you draw it down to nothing is when you need to be worried.

 

Is there a safety device installed that monitors the psi and shuts down the injector pump when it gets starved?
A friend of minehas the same exact truck as mine, and his lift pump went out, it shut the motor down before the injector
pump was damaged. How was this possible?

 

Mine does this with the in-tank pump. It blew a fuse and the whole truck just stopped dead in it's tracks. I guess it is harder for the VP44 to pull fuel through the in-tank pump. You could also put a check valve on the fuel line that has an adjustablecracking pressure. Adjust it to the PSI you want and when it gets below that PSI, it shuts the fuel off.

 

the VP44 can pull fuel on it's own, however when you have the restriction of the lift pump that is bairley working in the way this is where the problem occurs. the VP44 will divert a certian amount of fuel for lubrication and cooling, however under low flow, or high demand situations, it will divert all the fuel it recieves to powering the engine.

the CP3 on the 3rd gens was designed to pull fuel on it's own, however to keep the injectors cool and to ensure the demand for cooling was met for the CP3 the lift pump is there. the Chevy Duramax uses the exact same pump as the 3rd gen HPCR's, only difference is the chevy's dont have a lift pump, the CP3 pulls it's own fuel. for the duramax just adding a FASS or walbro pump to feed the CP3 make a world of difference on those engines.