If your only running 17 -19 psi and your return line is at 15 your only using 2 -3 psi drop in fuel preasure that dont sound wright.You have got to puss that fuel through a orfice that it priety restrictive it will take the way of the leist resistence which is yor bypass line.The other pumps Holly Carter Fass they can pump what they are rated at but they only pump what is needed because they all have a bilt in reguator that just recirculates the fuel in the pump.I would love to know why they got away from the mecanical pump.
I mean why change it if it aint broke.I'm not here to argue these are just qwestions that are bugging me I have done a lot of pipe fitting with pumps of different size's and I have run in to alot of problems that some engineers have drawn up that just don't work.

 

"If your only running 17 -19 psi and your return line is at 15 your only using 2 -3 psi drop in fuel preasure that dont sound wright.You have got to puss that fuel through a orfice that it priety restrictive it will take the way of the leist resistence which is yor bypass line."

I don't think that is the case. I think you have to feed the pump fuel at a positive pressure and the feed pump will take it from there. The feed pump in a VP44 pressurizes things to 50 to 100 PSI, so it easily gets as much fuel as it needs, pressurizes it and dumps it into the return line.

I'd love it if one could push fuel through the VP44, but one can't. Thus we have to use the bypasses. A VP44 is like a CP3. It has a feed pump and only takes so much.

"The other pumps Holly Carter Fass they can pump what they are rated at but they only pump what is needed because they all have a bilt in reguator that just recirculates the fuel in the pump."

I don't know if it is a regulator or if that is all the vanes will develop for pressure. The Holley pumps for sure DO NOT have a regulator. They rely on an external regulator. I am not sure about the Carter. People speak of the Carter being able to make 20 PSI, so the regulator must be set higher than that, if it does have one. Thus when one is seeing 12 PSI at the VP, the regulator is NOT in use.

"I would love to know why they got away from the mecanical pump."

Whole bunch of reasons, like space on the engine cam, expense etc. The Dodge Cummins community is the only group of people I know of lamenting the loss of mechanical lift pumps ! The 94-97 Ford PSDs had mechanical lift pumps. The 99+ have an electric pump. I don't see them complaining ! Put a decent pump on your Dodge and you won't have any problems.

"I mean why change it if it aint broke.I'm not here to argue these are just qwestions that are bugging me I have done a lot of pipe fitting with pumps of different size's and I have run in to alot of problems that some engineers have drawn up that just don't work."

Maybe you are selecting the wrong pumps ! The thing is that a Cummins only needs 30 GPH at 15 PSI, which is NOTHING compared to a lot of other engines. People keep selecting carburetor pumps with maximum pressure ratings of 15 PSI and they... FAIL ! Surprise, surprise ! There is a guy on DTR that has replaced 6 of them !

Why not select a pump that is way, way more powerful than you need and run it at 25% of its rated load rather than an underpowered pump that needs to run at 133% of its rated load ?