Superduty

Thanks for the info and comments, guys.

"Fuel flows from tank to LP to filter to vp-44 inlet. It enters the vp-44 at 10 to 15 psi, the vane pump increases this to 25 to 100 psi depending on engine rpm."

So it is like the CP3. Now we are getting somewhere.

That vane pump supplies the internal pump pressurization for pumping, lubrication and cooling. All it probably needs is a constant 10 PSI supply to fill the vane pump and it is good to go.

And like the CP3 there is no way to force more fuel through it than it wants to take. Vane pumps are constant displacement pumps and once they are full that is all they take.

The orifice shown is sized to create the backpressure, just like the cascade overflow valve in the CP3. And just like the CP3, it should not be touched for proper pump operation.

A bypass set at 10-15 PSI is probably the answer here.

All we need are some flow numbers and a good regulator and things should work great.

For what it is worth, my whole "flow through" argument was based on the VP44 being like a VE or P7100 where the internal pressure is set by the lift pump. The VP44 is in fact, like the CP3, where it has its own internal pump for setting the internal pressures.

I'm glad that information came forward. Good job, MtRam and JBody.

J BODY

.....and thus my feeling is shared about how much psi is fed to the VP. I know I read this same info somewhere, but didn't want to mention it without some support or link to actual information.

Sea01Cummer

Nice work guys , we are going to get this thing yet. Once again there are alot of people who are going to benefit from this thread.

Stevo

043500QC

Yes, Mtram and Jbody, I understand how this VP works alot better now.

I`m of the same opinion as you Superduty, I think proper regulation is gonna be the answer here.

Superduty

I suspect that gasser EFI engines have some pretty good regulators on them because they have to regulate like we do. Lots of flow at idle when the engine isn't using much fuel and not as much flow at WOT because the engine is using lots of fuel. The spec for the Dodge trucks is 58+/-2 PSI, which is pretty tight. We would obviously need an adjustable regulator.

Has anyone looked in the parts books (at say NAPA) or the aftermarket for an adjustable EFI regulator. They might be a better solution than the Holley or Swagelok devices. Just a thought.

BTW: I know we need to regulate at 10-15 PSI. I quoted the Dodge truck numbers to illustrate the tightness.

043500QC

Yeah, thats an idea to Superduty. Someone should look into it. I`ve got a friend that works at Autozone, I may get him to do some digging as he was here helping us do some of this install (actually, he was here the whole time)

Its definately worth some investigation.

BTW, someone had said it earlier, and i forgot to comment, but congrats to you and your wife on the new baby.

Superduty

"but congrats to you and your wife on the new baby."

I think you got me confused with Scotty ! Our baby isn't due for 5.5 months. We just got over the nausea stage, which is something to celebrate though !

apwatson50

Adjustable regulators for EFI engines, even adjustable ones, have a vacuum/boost reference line. So as your vacuum decreased the regulator actually increased the pressure. Or on a turbo charged engine the reference line will increase the fuel pressure on a 1 to 1 ratio with boost pressure. But I suppose that if you left that reference line unhooked it should keep the pressure constant, however I don't know if you'll be able to find one that will regulate at 15psi, as most EFI systems operate at 40+psi.

Aaron

Superduty

"have a vacuum/boost reference line."

Not all of them. For example, the one on the 05 Dodge trucks does not have a vacuum line. The ECM senses intake pressure and adjusts accordingly.

Most are 40-60 PSI. I think some spring trimming would fix that.

Barry St John

I'm not ready for this - truck still under warranty but an idea is a idea. FWIW it seems to me that the pressure relief valve ( swagelok) could be installed in a bypass just upstream of the vp44 to dump into the existing bypass. The swagelok and the bypass would have to be large enough to handle the output of the walbro at 15 psi so pressure won't stack under conditions of low demand at idle or when starting. I think you would need to increase the size of the bypass all the way back into the tank with a high volume high pressure pump like walbro. One of the smaller ones might work well and you might even be lucky enough that the amps at the pump would be close enough to not set codes. You should be able to achieve relatively constant pressure at the vp44 reguardless of demand. I think that you probably could set pressure at 12 or so psi at the vp44 which would give you plenty of fuel with ease of starting and increased reliability.

043500QC

OOOOPPPPSSSSSSS, well congrats to both of ya`ll then.

Superduty

george7941 says...

"SD. The reason the lift pump power is reduced during cranking on 2nd gen. trucks has nothing to do with deadheading the LP. It is because full pressure to the VP causes hard starts due to overadvanced timing inside the VP. So the ECM runs the LP at half voltage during cranking and, once the engine starts up, supplies full voltage to the LP."

Superduty

This quote is from here.
http://www.holley.com/data/Products/Technical/Fuel Pump Tech Info.pdf

Note the reference to the pressure limits and the orifice size. I think that is why the Holley regulator is having an issue. I also think regulating a carburetor lift pump is easier because it will slow down as the pressure increases. The Walbro won't.

I think the best regulator for this application will be one designed for keeping the pressure steady on an EFI system. it will be interesting to see if the 1/2" Swagelok works.

LonestarCTD

Found this tidbit of info.

Source: Chrysler Master Tech Issue 2 Reference Book - dated February 1998

"Controlled by the ECM, the transfer pump uses pulse width modulation to provide two duty cycles: full speed when the engine is running and half speed at crank to prevent overpressure that could keep the injection pump from operating"

Just wondering if that same overpressure that can keep the VP44 from operating at start up will also keep it from operating when it's blasted by a full-blown Walbro fire hose? I know that I've seen somewhere, I think it was a Tech Manual where the exact inlet pressure to the VP44, minimum & maximum was listed, something like 10psi min and 14psi max. I'll do some hunting to see if I can find that and report back here if and when I do.

Superduty

I think the plan is to run a regulator in the bypass and feed the VP44s with about 15 PSI. It is irrelevant how much the Walbro flows or what its pressure capability is if that configuration is used. The VP44 will take as much as it needs and the rest will bypass.

This is similar to how my CP3 is plumbed except the CP3s have the ability to suck their own fuel and thus the regulator isn't needed in the bypass. (Although it could be used as well.)

I don't know who the nut was that though he could force 80 GPH through the VP44... (It was me... I was wrong...)

In case anyone is worried, I have a plan to reduce the fuel pump pressure while starting. But lets see if it is a problem before we get into it. There is enough going on here already.