Losing prime overnight/fuel pressure problem

[Rawze]

(06-25-2024 )Skman Wrote:  

(06-25-2024 )Rawze Wrote:  do an injector leak check on it, as per the video, and make sure it passes.
ref: http://rawze.com/forums/showthread.php?t...3#pid75483

If it will not get to 29,000 psi then the pump (or its regulator on the back side of it) is bad.

as far as fuel draining back.. the check valve in the Davco is failing?.

I think I have a problem with my parking brake switch because when I tried to do the injector test in InSite...it won't let me. Says the parking brake needs to be engaged even tho it is.
I'm not sure if that's messing with the fuel leak down test as well? It'll let me do the test but maxes out at 13,000. When I was doing the rail leak down test it will sit at 13000psi...but if I slightly press the throttle during the test... it'll go up to 28,000.
Also, there is next to no leak after turning the key off/on. Over a few minutes I lost about 400psi.
I'm going to run a clear hose test to see if I'm sucking air somewhere from the tanks next.
I have a PACCAR fuel/water separator so I'm not sure if they have a check valve? I know my Davco on another truck does.

you should not have to rev engine up to make more fuel pressure. if so then the pump is not providing proper flow at idle. when doing the fuel leak test ... add the commanded fuel pressure to the monitor list along with the fuel measured. See if it is being commanded to 30,000 psi during the test at idle. If it is and it is not reaching it... then the pump is basd.. or you have a problem with the pump.

The difference between command and measured should always be within than about 300 bar or so... even at idle.