Ok guys could use some input. My truck is y2k 24v auto with a fass 95 lift pump and an reman vp44. If I parked it up hill it has to be reprimed in the morning . (Starter bump type) I put in a check valve on the discharge side of the lift pump by the tank which solved the priming/drain back issue, but I don't know why the fuel was draining back. I have no leaks and no

smell and run 14-16 psi on the fp gauge. When the truck is at lower rpms under load light or heavy I can feel a little bit of surging like a miss. All of the return lines seals have been replaced already . If there's is a leak how can I find it and could it be in the injector pump check valve. Thanks for the help

Edited September 15, 20159 yr by jigdog

19 hours ago, jigdog said:

Their vp rebuilder thinks it's 

the vp and it has a leak inside in the pump part of the vp.

 

Ummm... There is only the front seal... Which would be dumping fuel in the gear case... The working outward on the pressure side is the cross over tubes. Now did you install or change injectors at all? Really common for people to install injectors the wrong way and cause a leak inside the head where you can't see and just return fuel to the tank. Suction line leaks never actually leak and the toughest to find because while the engine is running the suction line just draws air in and mixes with the fuel. If your running an AirDog or similar then the air is just returned to the tank. Now when the truck is shut off then suction line will still draw air in allowing the supply line to drain back. Personally I've never heard of VP44 being the cause of a loss of prime.

All of the tube seals were replaced by the shop ,along with the fuel line between the filter and vp.they also ran a clear line in the same spot to check for air and none showed up. The only two consistent things are if you crimp the intake side it doesn't loose prime. When the shop had it parked up hill it started after overnight sitting,but when I drove it home and it sat uphill it loos Es prime.i think they were not really road testing it etc. seems like to me one of the pumps is leaking back after running a good distance.if the return side was leaking air then it would loose prime when the inlet side of the vp was crimped off right.

On May 22, 2016 at 1:02 PM, notlimah said:

I have a hard time believing the leak is coming from the VP44, especially since you got it from Vulcan. I've never heard of a prime issue being because of a VP, especially a new/rebuilt pump.

 

 

In that pic, have you replaced the washers for #4 & #5 in both locations?

Have the grommets that attach to the #3 been replaced?

Have the crossover tube o-rings been replaced?

Have you made sure the return line on the FASS is tight or any washers or o-rings are in good condition?

 

It would just suck to shell out money for a new VP and it doesn't fix the issue ya know?

 

The vp is 5 years old so I have had it for awhile.

@jigdog Did you ever get this issue fixed? I had mine fixed for almost a month and then it all of the sudden came back.