Return style regulator with a aftermarket lift pump

[Bigsaint]

Alot of good information by all, I hope that the newer members are reading this. I have not forgotten the work you did, Mopar M, and I commend you for your R+D. I was told by Mike at Auto Wurks back in Jan. , "you do not want much more than 12 psi's going into the VP44, there is a seal in the VP44 that can fail at high psi's". Another quote, by MoparM "remember pressure is a restriction to flow after you equalize flow thru all your orifices " really sums it up inregards to high psi's IMO. I attached a flow chart from Century that shows the flow rate of the Mallory 140 series pump. Note how the highest flow is at low psi's.



Scott W.

 

[Bigsaint]

My thinking, after looking at the flow chart for the Mallory is, lower psi's at WOT equal a good thing, within reason. Zero psi's at WOT would scare me because that's a bit too close to negative pressure for me. For me, 2-3 psi's at WOT wouldn't be such a bad thing, as long as I wasn't encountering a stumble at those numbers, I would believe that I had good flow/volume. The funny thing with the Mallory, and I've stated it here before, while in a WOT run, the initial psi's drop down to 6 psi's or so, but it recovers very quickly and is back up to 8 or 9 psi's, while still in the run and pushing hard. Guess that the initial lower psi's are the VP44 calling for more volume, once it gets what it needs the restriction is back in place and the psi's go higher.



Scott W.

 

[Mopar-muscle]

glad to see we are on the same page ....

tommy first , i just threw up my time with the stock system as an example of what the stock sytem is capable of, it is by no means the correct way to be doing things . being the procrastinator i am is the main reason my carter HP is still in the stock location . my present system is 15 psi HP carter in the stock location , stock pickup and lines to the pump , my own setup of adaptors , -6 lines and fittings after it , plus some mods to the internals of my stock 2000 fuel filter .



a stock filter flows roughly 45gph from what i have been told by someone that actually tested it ( bill k. ) and my mods have gotten me closer to 60gph . again laziness and fixing other peoples cars has kept me from testing out my mods and moving the pump rearward . my final system will have a stock lift pump and lines with the stock pickup in its factory location , then an HP pump of some sort back at the tank with probably -8 lines ,( though a fluid engineer that was paid to acess the dodge fuel system said the stock lines were just fine for the 500 plus flywheel hp range , where most of us reside) , i will have it setup so i can switch from one to the other if the HP system goes belly up and not leave me stranded , earls makes a nice ball valve that i think will do the job nicely .



i guess what my rants are towards is the idea that at WOT you need to have more than 14psi of fuel pressure ... seems that people are beginning to realize that is NOT a good thing . anyone that gets a warm fuzzy feeling from that much fuel pressure is entitled to it , but do your wallet a favor and regulate it with a direct return back to the tank , there is a reason that you see more than 14 psi , its because its being stopped by the inlet of the VP44 . if the overflow valve was returning the actual inlet pressure then we shouldn't see more than 14psi , this is my thinking , again i'm not positive , i need to tear apart a VP44 , anyone got a dead unit i can fondle ???? even better is the graph big saint put up ... very good scott ... the lower the pressure , the more the flow , look at a garden hose just pump into a bucket with nothing on the end , whats it pressure ??? basicly 0 , there is no restriction to flow , now put your thumb over it , now you have pressure and a restriction to flow . when your inlet pressure drops to 0 the pump is using all the fuel that is being pumped to it , and 70% of that is going back to the tank via over flow valve and what is coming out of the head after the injector closes , once you start seeing a pressure increase you are giving it more fuel than it can use , which isn't a bad thing , to a point . my warm fuzzy feeling is around 5 psi .



as far as the VP44 being able to draw fuel , it must not suck much since there is only maybe 2 inches of fuel in the filter available till it sucks below the 2 holes at the top of the center post of the filter , once it sucks below that and you aren't filling the filter housing via a dead lift pump the engine will stop running (want to try this theory , disable your lift pump and see how long till the engine stalls out , maybe someone will prove me wrong , god knows i need to be slapped down a notch ). thats why i added more holes , though i added too many and am able to draw as low as the WIF sensor .





my head hurts ... did i miss something ???

 

[Bigsaint]

Mopar, when my first Mallory 4150 died the VP was doing just that, sucking fuel at minus 11 psi's, according to the SPA gauge, at idle. I don't know how long it was running that way because all was fine with the FP when I left the truck running, went into the hardware store for, of all items, a bracket to mount the TST box, lol, came out after maybe 10 minutes max. and found the negative reading. At first, figured the SPA sender was going toes up, tried to drive out of the parking lot and it just didn't feel right, shut her down, then tried to restart with no sucess. Tried bumping the started and the Mallory was dead quite, no start. Checked the wiring connections and then re-tried to bump start, no sound from the Mallory and 0 FP psi's. For some stupid reason, I tried to crank and the truck started again, but with the -11 psi's FP reading, seems that the Mallory was not yet completely dead yet. The truck ran at idle with -11 psi's for about 30 seconds, then I shut her down as I was more than a little concerned about the health of the VP44. That's when the flat bed was dispatched and the damage to my front universals occurred, but I'd rather not re-live that episode. Don't try this at home !!!!



Scott W.

 

[Mopar-muscle]

ok , i may have recieved that slap , but you were getting some type of fuel flow you seem to think , tomorrow i'll start my truck and unplug the carter pump and see how long before it quits , maybe take it for a spin ... its only money

 

[Un-Hemi]

BigDaddy, I apologize for calling the overflow valve a "bypass regulator", but that is what it appears to be. As per... "the Overflow Valve's ability to regulate pressure to the injection pump. " To prevent further confusion, I shall call it an "overflow regu... uh, valve"



The quote from the service manual that starts: "Fuel from the fuel transfer pump will always provide more fuel..... " is wildly optomistic, in my opinion. Wishful thinking, as it were. In an ideal world, perhaps.



It's my belief that the bypa... uh, overflow regu... uh, valve sits in the same chamber in the VP-44 as does the inlet fitting. If both the inlet fitting and overflow valve are removed, I suspect that one could blow in one hole, and tickle his ear out the other. OTOH, I would be pleased to be proven wrong, because we will have gained some insight. If no one responds, I'll check it out when I do my lift pump, after my $tupid Caravan i$ repaired.



MM, it appears from your experience that when the lift pump is functioning properly, and the fuel filter is clean, then the system is capable of supplying enough fuel to keep the VP-44 inlet pressure positive. That's what we are after. Your fluid engineer is probably correct about the stock fuel lines. Back in the good ol' days, I ran a 64 Max Wedge car that put out about 525hp. I used the stock 1/4" fuel pickup in the tank to feed the thing. It never ran out of fuel. Ever. 7psi through the eyes. Except when yours truly forgot to fill the tank. I see little need for anything larger than 3/8" in this discussion.



MM, I'm wondering how you attached your stock fuel supply line to the Carter HP? Is there such a fitting as a quick connect to NPT or AN?



Is it appropriate to use a bypass regulator with an internally regulated pump? Seems like it would be redundant.



One pump is enough. It's easier to change if it's back on the frame rail.



These are only my opinions based on my experience. Your experiences may lead to different opinions. That's good. Concensus is difficult. Objects in this monitor may be closer than they appear. Some is good, more is better and too much is just enough! I know when to quit. I never lie. Trust me.

 

[Mopar-muscle]

tommy , i took the inlet banjo out of the system , removed its holddown bracket and bushing , hacksawed off the banjo head and connected it to the pump via a 3/8 npt right anle to 3/8 compression fitting , this let me connect it right back to the stock line . of course now i have to buy an new one to put the stocker back in .



as far as the regulator on an internally bypassed pump , yes its redundant , but if you still have to much pressure at the inlet to the VP44 , you still have the potential to damage something that is 7 or 8 feet from the lift pump now mounted back at the tank ... going to pull my lift pump wire ...