Engine/Transmission (1998.5 - 2002) I want a pusher

[RADdodge]

I believe the 8 psi that Dodge is referring to as the minimum Lift Pump pressure is in reference to their standard of what constitutes a bad Lift Pump and not what pressure is needed to keep a VP-44 healthy. BTW, the Racor check valve that Eric is using automatically bypasses the pusher pump when that pump is not operating, no manual intervention is required.

 

[Gary - K7GLD]

" BTW, the Racor check valve that Eric is using automatically bypasses the pusher pump when that pump is not operating, no manual intervention is required. "



Good deal... Actually, I sorta interested in a full-time bypass - as long as it meets the requirement of passing ENOUGH fuel to reasonably operate the VP44 if the pusher fails, YET, bypasses enough to reduce the head pressure on the pusher. My Carter 4600 is VERY noisy if run with engine off, drops to an audible but acceptable level once the engine is running - I suspect that a 1/4 inch bypass would drop pump noise down into the inaudable level, and reduce the strain on the 4600.

 

[Ncostello]

Gary, the full time by-pass is a neat idea. I think that a bypass check valve takes some amount of suction (pressure) to keep it open once a pusher dies. That suction required to keep it open and fuel flowing has to be created by the stock lift pump up there on the engine. So it would have to work that much harder to pull fuel through the check valve. Seems like the stock lift pump has enough trouble pulling from the tank alone much less a check valve in the line. I mean would someone put a check valve on the supply line of a totally stock truck without a pusher... no. It would be a big restriction. But I am new at this so I could be way wrong. Apparently others have done this with success.



The only thing I wonder about the full time bypass loop would be if you would loose pressure cause the pump might rather pump fuel around itself cause its easier for the fuel to go through the short bypass than go all the way up to the engine through the fuel supply line (friction and pressure head is greater all the way up to the engine). Again I may be completely wrong. But I wouldn't be afraid to try it at all. The results may be great. Probably will work. Sounds neat.

 

[Gary - K7GLD]

"The only thing I wonder about the full time bypass loop would be if you would loose pressure cause the pump might rather pump fuel around itself cause its easier for the fuel to go through the short bypass than go all the way up to the engine through the fuel supply line (friction and pressure head is greater all the way up to the engine). "



Neil, that's why I mention the use of 1/4 inch bypass line - the goal being to provide a SMALLER bypass path than the MAIN flow thru the larger main line - admittedly, there may well be a "balancing act" involved to arrive at my final intended goal, but I'm pretty sure it can be done, tho it may involve judicious squeezing on the 1/4 inch line, if needed, to "adjust" constant flow rate and psi... But I *do* know that with FULL head pressure, the Carter push is LOUD, and obviouly laboring under what is a total restriction - and STILL louder than I like when the engine is running and reduces pressure somewhat...



I'm ordering another Carter 4600, and will make up a complete duplicate of what I have on the truck now, but including the bypass, and after I have more miles on the existing setup, especially the added filter, will simply swap out the whole setup - I have to pretty much pull the whole works anyway to change the filter (really no big deal), so this change is no problem, and if the newer setup proves to be an advantage, I'll then modify the original one still in the truck...

 

[RADdodge]

Re, the “by pass valve” (Racor check valve). The check valve opens at 0. 5 psi. I could not detect a difference between running our rig with or without the pusher pump installed when the pusher pump is disabled. I ran the rig from the Southwest U. S. A. through Alberta and British Columbia, Canada with the pusher pump disabled without a hint of low fuel pressure or performance loss (see sig or pictures). I wouldn’t worry about a good lift pump pulling fuel from the tank (and filter) through a check valve. What causes the check valve to close is pressure from the pusher pump. When the pressure between the lift pump and the pusher pump drops below the threshold, the lift pump will suck fuel from the filter directly. In other words, whenever the pusher pump cannot supply enough fuel, the check valve opens. Unless the check valve malfunctions in an open state, the fuel cannot recirculate. Even if it did, the lift pump could still suck fuel through the filter, abet with lower total output pressure. As it is now without a pusher pump, there is no pressure at the lift pump inlet anyway so what’s the difference – very little. The simplest and in one sense, the best way to “fix” this particular problem is to install a filter and lift pump back at the fuel tank. No redundancy, but a set-up like that should last a long time. Most of the time, simpler is better.



BTW, the way our pusher pump is installed and wired, there is no noticeable noise from the pusher pump (see pictures in Readers Rigs). I. e. the lift pump is more noticeable.