Engine/Transmission (1998.5 - 2002) New VP44 Theory???

[WeirCummin]

2 Solenoids

Nowel, you might want to rethink what the second soleniod does. The one in the distributor head is the high pressure solenoid valve. The other one sitting below that is the timing device soleniod valve, that in conjunction with the timming device piston assembly controls the cam ring for timing via the FPCM. Anyone can order the VR series pump book from Bosch @ http://www.boschservice.com/http-docs/access/booklets.html#DieFueInj The booklet # is 1 987 722 174. It's the best $8. 00 I've spent on my truck.



NXS and I tore a pump apart yesterday that I had replace due to a timimg control problem. The amazing thing is that we were able to put it back together. It's to back that the only way to test it would be to put it back on a motor.



Dean

 

[HVAC]

Ooops!

That makes sense Dean, there has to be a way to alter timing.



So, how is cooling fuel regulated, or is it?

I'm assuming the cooling fuel is at 200 psi and is after the internal sliding vane pump. I'm guessing that all the fuel entering the pump passes through the internal sliding vane pump.

 

[WeirCummin]

Matt,

Even though the overflow valve is in the closed position there is still fuel flowing back to the

tank via a throttle bore located within the overflow valve. The injector pump is completely

filled with fuel. Cooling and lubrication are not dependent on injector flow.



Lets look at this scenario, for those with FP gauges. You bump the starter to cycle the

lift/transfer pump, it runs and builds the the maximum pressure that the pump will put out (in

my case 13. 5psi) When the lift pump stops, the pressure drops back to zero or should.

Where did the pressure go, out the injectors, back through the lift pump ?? Neither, it

returned to the tank through the injector pumps overflow valve throttle bore.



Nowel & Tommy T.

I don't know what the output pressure of the vane pump is (I'd hook up a gauge if it was

something I thought was important) The vane pump supplies the HP pump distributor head

from a pressure kidney (pump output) through a passage in the housing. On the inlet of the

vane pump or suction kidney there is a throttle bore that supplies fuel to the internals of the

pump, though it is not under the pressure that is sent to the HP pump.

Sound like Royal knows what he is talking about and not just speculating.



Dean

 

[JerryWallace]

the vp44 will always return some fuel to the tank



jerry

 

[JerryWallace]

vp44 fuel return

 

[HVAC]

VP44 Overflow Valve

That's helpfull!



I've had that little critter out before to check for low fuel problems, but I missed that second circuit. With the second circuit you won't have a condition where the cooling fuel in the pump gets excessively hot.

 

[Un-Hemi]

This is a significant observation, Dean. In fact, however, a vane pump can allow pressure to be relieved back through itself, as there is no check valve in most of them. The vent in the overflow valve will do likewise.



Matt, I'm not sure that this information is what you had in mind when you started this thread, but here is a quote from the 'Pumps, Lines and Whatnot' thread. I believe this applies to the 215hp engine:



"In issue 29 on pg. 48 is the info about BSFC. It says 2000rpm/. 334 and 1600rpm/. 337 and from the looks of the microscopic graph that was included, 3300rpm/. 4. I believe that all of these numbers are lbs/Bhp/hour. "



This establishes the fuel requirements of the engine, and does not take into account the bypass and cooling flow of the VP-44 that is returned to the tank. Nowel's figure of 70% return to the tank is probably accurate. This should establish the lift pump requirements for flow.



Matt, have you cracked the overflow valve open with just the lift pump running yet?



Royal, if the overflow valve didn't relieve the lift pump, it seems to me that it would be impossible to prime the system after changing the fuel filter. There is no other way to bypass the entrained air back to the fuel tank.



Is it possible that the overflow valve has the function of maintaining housing pressure at approx. 14psi, regardless of whether it is generated by internal leakage or by inlet (lift pump) pressure?



The difficulty with lift pumps has not so much to do with pressure and flow, (it's been suggested that any positive inlet pressure seems adequate) but has more to do with longevity. The MTBF (Mean Time Before Failure) of the stock lift pump (and many attempts at replacement) sucks!





Tom

 

[Royal]

Happy 4th of July. Some of you are close to being fuel injection technicians. The overflow throttle valve most definitely controls housing pressure and return fuel. All of the lift pump fuel via the filter goes directly to the inlet of the vane pump. The vane pump pressure is regulated by the adjustable pressure control valve that is mounted above the pump in the front end of the Vp44. The valve regulates press. by dumping the exces press back to the inlet side of the pump. I have beem told they calibrate the vp44 using a 15bar gauge. (1 bar =14. 5psi) there fore I would guess the press is set somewhere less than 200psi, which is high compared to other rotoray/distributer pumps. The vane pump pressure is dependent on RPM,which is low at start & increases with rpm until the pressure control valve limits it. The internal componets ,ie. valves,pistons,vane pump,plungers, selenoids etc. do not have seals,they are all close tolorence finely machined/honed fitted components. They all have some leakage which goes into the housing cavity. The main distributer rotor assembly that produces the high pressure fuel and distributes it to each injector line ,also has a return flow passage to the over-flow valve . There was a question, how does the lift pump bleed the pump after filter chg. The fuel forces the air out thru the throttle orifice of the overflow valve. NXS -has a good photo of this on his post. The throttle hole must be fairly small,which is why it takes time to bleed. The prime purpose of the orifice is to vent the air bubbles out of the housing. On another post about hard starts with add on lift pumps. They designed the system for 7psi start fuel. If you exceed this ,at some point the high pressure plungers can not charge at cranking RPM which results in hard starts.

 

[jerryrigg]

Tom-

No I have not cracked the valve yet. Royal is making sense to me regarding housing pressure so at this point it would most likely be a waste of time. I have not taken Royal's word as if it were from the burning bush yet but it looks to me like he knows what he is talking about on this pump. I am ordering the CD from Bosch to educate myself.



Royal-

Thanks for all your input



-Matt

 

[JerryWallace]

If anyone has a web site or a way to post a full view of the vp44, E-mail me I can send it to you to be posted. The file is to large to post on this forum.



jerry

 

[BK]

Jerry's Pix

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[Diesel Freak]

Re: paging Dr. Freak....Dr. Diesel Freak.........

I'm here!

 

[HVAC]

WOW!

WOW!



I can almost follow that schematic.



Quite cool8)

 

[WeirCummin]

Here is a dissasembled ETC /027 pump.

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[Steve Campbell]

I am still wondering....

About Cummins 10 psi minimum lift pump pressure vs the 14. 5 lb crack pressure of the overflow valve. Royal and jerryrigg have engaged a right-brain... left brain :-{} . I am curious to see where this discussion (not mine-but yours) goes?

 

[HVAC]

Bleed Orifice

Steve, the boys showed above where the pump casting has an orifice to let fuel flow back to the tank even with the overflow valve seated. When the pressure increases and the ball lifts, even more fuel can exit the pump housing.



So even at 10 psi or less, some fuel is going to bleed past the overflow valve and work it's way back to the tank.

 

[ScottWright]

The diagram posted above is GREAT!!!!! I was just wondering one thing though? Can someone explain how/where the fuel is transfered to the center of the delivery pistons? As far as I can tell the diagram doesn't really show that. Also, on that diagram, what is the piston spring area just to the left of the #4 high pressure solenoid? Is that possibly the internal low fuel pressure bypass from the vane pump pressure I was thinking you would have to have something like that built in, otherwise the pump as it got older and wore the vane pump out (lowering pressures) would change your starting pressure inside the delivery piston bore. Since it looks like there is no pressure regulator for the high pressure side, this would cause a decrease in injection line pressures causeing less fuel, less power, etc. . .



I wonder if you could shim that internal low pressure regulator piston/spring assy. that would cause higher internal pressure to start with in the delivery piston bore. Higher pressure will effectivly keep the injector open longer. Same effect as holding the high pressure soleniod valve closed longer, without increasing the duty cycle for that solenoid? Anybody want to comment? . . . . .

 

[ScottWright]

actually after looking at this further, the low pressure (vane pump pressure) regulator is that peice on the upper lefthand side of the pump. So that leaves me to ask what the heck is that thing to the upper left of the high pressure solenoid? Mabye some type of resivoir for something, or pressure dampner? Dang too many questions and not enough answers!!!! And agian I guess I ask, couldn't we just shim the spring in that low pressure bypass regulator to create more starting pressure in the delivery piston bore? I assume the injector would have a longer open duration, but the computer would compensate with lowering the high pressure solenoid duty cycle at idle to compensate. Anybody wish to comment about what we can do with the advanced timing from this too? Maybe no timing box would be needed? What do you guys think?

 

[IRNGOAT]

vp44 fuel return

Can yhis part be purchased sepratly from Cummins ? P/N anybody ??