rail pressure problem
 

cousins truck and im no duramax pro.

he has been bit by the bug and is well on his way to the DARK SIDE lol. just had a 5 position EFI put on the truck. i road with him to get it installed. after installation we ran the truck around with the laptop to monitor things. rail pressure is way off. desired is 26k and @ wot we are dropping to 12-13k. i absolutely believe this has nothing to do with the tuning as it does it on all settings. if takes off well than falls on its face. the truck only has 60k on the clock has a slight knock/rattle i believe to be fuel related. i strongly feel like the CP3 is failing. could a failed relief valve or the factory lift pump cause such dramatic pressure drops? the truck runs pretty good and to the novice runs out well. power balance is even and injectors test good. fuel filter was replaced about 500miles ago and he tells me it drove the same both before and after.
a little insight would be nice.

thanks

the duramax doesnt have a lift pump the CP3 pulls fuel all the way from the tank. also CP3s failing is a rare thing

i believe he found the problem last night. he gave me a call and told me his fuel filter was loose and only had about half a canister of fuel in it after removal. gonna play with it today but it was most likely sucking air. strange because it started and idled great? if that was his problem what a retard. LOL

yeah that could be it lol if he's looking to build power I would put an fass or air dog on it good for power and CP3/injector life

have you read this thread?
 

https://www.dieselbombers.com/lb7-pe...-fittings.html

I'm not sayin' it is, but not ruling it out either.

jerry

Fuel pressure dropping off
 

The problem your buddy is having is the exact description of what is going on with my 01, Is his going into limp mode P0093 ? Because i know my filter is tight an no air getting into my fuel system.
Thanks
Oleoleson