Superduty

Woah, Smokin. You've got some 3rd gen stuff mixed up in here that the 2nd gen guys don't have to worry about.

"the low pressure supply line goes into the filter from the tank pump right?"

Yep.

"......the return line starts @ the relief valve on the back of the rail...then to the filter"

On 3rd gens it looks like it goes into the filter, but really it just connects with other lines there and goes back to the tank.

"I am assuming that's where excess fuel is flowed back to the tank from the filter ? Help me out here guys.... so before the "new style pump" where is the fuel regulated or does it just fly through the filter back to the tank?"

It just goes straight back to the tank.

"Is this done just by voltage reg to the OEM pump in tank to control pressure?"

There is no pressure regulation in these systems when the engine is running. The pump pumps all it can and whatever flow/pressure develops, develops. I tried to emphasize that when comparing these pumps. When you put the Walbor on these trucks, suddenly there is too much flow and pressure and thus relief systems must be used.

"Also the return line regulator idea is not going to work if you ever blow the rail valve..."

2nd gens don't have a rail valve. And on the 3rd gens they would have to push the fuel backwards against the Walbro to get into the CP3. The fuel that relieves from the rail is at 26,000 PSI in the rail, but it is only at 10s of PSI after the rail relief valve. It will go harmlessly back to the tank, which is the path of least resistance.

Sea01Cummer

Where exactly is this relief located?

Steve

smokin05

Sorry about the third stuff flying out! Whoops I was only concerned w/ the hydrostatic pulse if the return line is full of fluid and the relief pops...its gonna be hammer time ....on the 3rds only if the reg valve was in the return...

I want to do this on my third to protect my frail vp pump...but I thought a reg valve would be in order also am I mistaken?

Superduty

Sea: I think it it built into the banjo bolt that connects to the return line.

Superduty

"I want to do this on my third to protect my frail vp pump...but I thought a reg valve would be in order also am I mistaken?"

Your third <gen> truck has a CP3, not a VP44. You can run a regulator if you want to. Its your truck.

Sea01Cummer

I have a spare motor that i could take this thing out of and modify it to try?
All i need is more hours of daylight.

Steve

smokin05

Whahoo cp3 r2d2 what? i thought it was a vp44? no? is that better ? or like i am afraid worse? i have read enough lift pump dies and takes out injection pump threads on here i just assumed a aftermarket was in order....is the cp3 pump/lift system any better?

linetrash75

Seacummer, the "relief valve" I'd classify it as a check valve, is to keep fuel in the VP when engine not running, the larger banjo bolt under and in front of the supply banjo on the VP. To gutt it I simply took of the VP out of return line put punch on the inside and drove 1 large ball for sealing purposes, then a spring, a then little ball that serves as check ball, then drove larger sealing ball back in, note this destroys your "relief valve" if you want to put it back together the way it came out, so have another if you want to restore to stock. If you gutt it please do a volume test and post results.
Jed

043500QC

Smokin, your 05 does not use a VP44 injection pump, it uses a CP3 injection pump. Your CP3 pump should be plumbed just like Superduty outline in his other thread about Implementing a Walbro pump. This discussion is strickly about a VP44 equipped truck.

And before any of the naysayer`s start, as soon as we figure out my Dad`s truck, I WILL BE INSTALLING THE WALBRO SYSTEM ON MY 04. I have that much confidence in this pump after seeing how much more flow it offers over the stock pumps.

043500QC

Amen bro, we`re gonna figure this out.

Right now, we are just waiting on the larger Swagelok before we can proceed any farther, but this conversation is definately shedding alot of light on the way these fuel systems work. More information is NEVER a bad thing.

smokin05

right i just figured out the whole vp /cp3 issue...sorry guys my bad!

by the way superduty i read your cp3 post i am gonna try it soon.... good post! thanks i am all straightened out now folks!

good luck w/ the vp thing guys !

J BODY

FWIW....the upper holes are the inlet and return. The one on the left with the small orfice is the return. You're not going to get much flow through that keeping things at 15psi.

Superduty

Good work, JBody.

What would you estimate the diameter of that orifice to be ? 1/8" ?

Is that the most significant orifice in the pump ?

What is behind the orifice hole ? Err... if one was to say... drill it out, would the drill hit anything behind it ?

Is there a path from inlet to outlet (to that orifice) at all time, even when the pump isn't turning ?

If that orifice is 1/8" or larger, it is comparable to or even has more flow potential than the CP3 bypass line... see where I am going with this.

If it doesn't, it isn't something that a drill bit couldn't fix.

J BODY

http://www.tdr4x4.com/files/vp44-pic.jpg

Mt Ram

Just a little info for you guys to consider. In a past life I rebuilt diesel fuel injection pumps. This was before the Bosch vp-44 time. The vp-44 is a distributor type pump where there is a rotor and pumping plungers inside. There is also a rotary vane type of pump that is the low (around 100 psi at wot)pressure part of the vp-44. 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. This higher pressure fuel then fills the plunger cavity. The plungers build pressure until a port in the rotor lines up with a port in the head. When these ports line up the fuel is pumped to the injectors. So the plungers are the high pressure part of the pump.

If you feed the vane pump to much inlet pressure it will cause the head and rotor to seize, and now your vp-44 is a piece of junk. Also consider that if you force a liquid through an orifice you create heat and that is exactly what you would be doing if you try to force 80gph through the vp-44.

I think that one of the smaller walbro pumps may be the answer but it will probably require a seperate return path that does not travel through the vp-44.

Remember, this is my opinion only!