losing fuel pressure overnight ?

[BoeingDiesel]

Tinman, have a look at the left side of your injection pump where the two fuel lines are connected, and if you can, take a picture and post it. It's a long shot but just maybe the installer did not install the check (overflow) valve on you IP. It's a long shot but with your description it sounds like the pump is draining down. If the valve is installed then perhaps it needs replacing. This is one of the basic procedures when you install a VP44 to crack the check (overflow) valve and bump the starter and wait for fuel to come out to confirm that you have primed the VP.

 

[Tinmanroy]

Will do tomorrow, then post. Thanks

 

[JR]

How about if you fill your fuel tank, any difference?
Factory fuel modules are a known problem area over time but doesn't really match your symptoms unless the problem goes away with a full tank.
To make sure I understand, none of this showed up until you installed your new pump? And you are 100% sure on the install?

 

[Tinmanroy]

Yes on the install and I never let fuel less than 1/2, generally fuel.

 

[JR]

Is your Fass mounted on the frame?
If there is a leak on the suction side it will generally draw air allowing a siphoning effect back to the tank . Makes it difficult to track. The same can be said for the return line back to the tank including the tee at the back of the head. Since it's not under pressure they often don't show as a leak unless it's a bad one. If it takes a day or more to generate a hard start it's not a bad leak yet .

Since this didnt surface until the install I'd have a good look at the suction side, between the tank and Fass.

I just read through your posts and didn't see mention of replacing all the washers and grommets on the return side. If they are original or the lines have been disturbed recently that could be a source of drain back due to siphoning also .

There are o rings that attach to #3 that are known failure points over time. Same with #4 & #5 in both locations. #6 is the overflow valve on the VP, but if you have good fuel pressure once the truck is running I'd wager that it's operating as intended .

 

[Tinmanroy]

Ok, I have a lot to check

 

[Tinmanroy]

I took a few pics.