Ok... I got a few question for the LP / VP44 Guru's...

I've got my cruise set for 65 MPH on flat ground and my boost is not changing. But the LP pressure is dropping to 10 PSI then rising back 12.5 PSI then falling again... Cycle continues randomly.

CURRENT PSI NUMBERS

16.5 - Starter Bump - This number has gone up 1.5 PSI since new...
14.5 - Idle - This number has come up as well about 1 PSI
12.5 - 10.0 - Cruise set @ 65 MPH flat ground
7.5 - WOT - No change here...

1. Is this a sign of failing LP? Even though it passes the volume test.

2. Is there a pressure regulator on the VP44 that could be causing the problem?

This is just plumb strange to me... Ok Guru's go for it! Tell me what you think???

 

LP is dying. IMHO

Answer to number 2 is yes. Its internal in the LP. Suspected of being the largest cause of failure, and my theory is the engine vibration damages it.

If you get a new one take the old one apart.

 

Has anyone noticed a lower fuel pressure on hot days? Keep in mind that I'm in FL.

 

My relocation of the LP may or may not be a factor in the following. My #'s are 17-idle,16-cruise, 14-15 WOT. I have not noticed any difference on hotter days.

 

Should this effect my TOM vote??? Does the winner have to be a running truck?



Just kidding buddy!

 

You can't kill a good cummins... It still runs good just some really goofy looking pressure readings at times....

Oh! Am I in the TOM list???

I really don't want to drive all the way down to the dealer yet... I think I will let it delevope a bit more before I run for the dealers...

 

My lift pump pressure increases when the fuel warms up. Maybe the pump clearances tighten up when it gets warm.