cummins missing a beat?
 

hey guys, just wondering whats causing my truck to have a rough idle after coming to a stop or after reving it up. it almost sounds like its missing a beat. if you let it idle for a little bit like 30-45 seconds it smoothens back out. other then the idle issue it runs the nut. cleaned the iat, and map sensor thinking it would help, and nothing.

what lift pump you got and how olds the vp44

lift pump looks to be stock, and not to sure on the vp. i got the truck at an auction so i really have no back round history on the truck. the pump does say remand but looks pretty dirty so its nothing that was recent.

check it for codes to see what it brings up. its sounding like the lift pump has went out and killed the vp44 and with the lp down it will be loosing power and missing.

i dont think the vp is shot because it starts up fine no white smoke, and it puts the power down pretty damn well. i scaned it when i got it and there was no codes, but ill give it another shot an see what it comes up with.

What is the fuel pressure to the VP44? Below 10psi to the 44 is bad.

dont have a guage....

it can easily be the lift pump though really need to check the fp on it

i check the fp. with engine not running, but lift pump running its 19.5 idling its 16-17, and when revved it drops to 14-15 range. so i dont think its the lift pump. gonna change the fuel filter soon and see what happens....

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scanned it for codes, came up with nothing.

well then next on the list would be chase the fuel lines from front to rear checking all the fittings and lines for air leaks, air getting in can cause that as well.

if there was an air leak would they be dripping? and the psi numbers that i listed above sounds like the lift pump is good right?

ya but what is it under a load. and not if its on the vaccum side of it and not the pressure side. or it could be internal like an injector or connector tube leaking. then it would be returning through the return line back to the tank or getting burned

VP44, APPS, ECM, or Bad Injectors.

the psi #'s i posted where done in park really have no way to test it when under load cause the guage is under the hood, it was just a tester guage that screws into the port so i had no hose to string inside the cab if that makes sense. and i just looked over the lines from lp to tank, and saw no signs of a broken line that could be letting air in.they would be wet if there was a leak.

codes?:w2:

nope no codes.