VP44 Injection Pump Teardown - How it Works

[wil440]

5 hours ago, W-T said:

So guys, gals...I'm not specifically calling anyone on the carpet here. @wil440is sleeping right now (4pm west coast time USA) when he says it ONLY piddled in the bucket and others also had similar observations... I have to review the shared data? 

WT  ...... in my testing with the fuel return disconnected from the basket and placed into the filler neck  with engine at idle and a fuel pressure of 5 to 7ish I had/have really good fast return flow to the point now of not bothering at all about 5 to 7 at idle, I didn't put it into a bucket to measure at the time as here in the UK fuel is too costly to waste 

My fuel temps show that there is good return cooling flow, I did 90 mile yesterday towing my mobile workshop trailer..... fuel temps at their highest was 95F and this was once off of the motorway and onto small backroads, motorway driving was sub 90F.

Also I have a DTT mechanical fuel lift pump which sits in cooler airflow,  contrary to where it's sited it does not get any radiator heat as it's just a little lower but I suppose the pump could suffer from heat soak from the sump face it bolts too

So my fuel test didn't show it piddling into a bucket, quite the opposite, also having a mechanical FP my pressure only goes one way with rpm, up, so idle is the lowest psi the system ever see's hence why I only tested at idle.

Also one other thing to add.... the only way I could get to the 14psi at idle recommended was to clamp off the return line to restrict it somewhat, not totally closed off though as I soon figured the DTT was capable of blowing the face off of my 30psi gauge, this I will add was only done while testing and for a second or 2 at most just to test what happened.

My return line is not the factory line as that split so I replaced it with 3/8th fuel hose.

 I'm ok with 5 to 7 psi on MY truck as I know from testing and fuel temps that I have more than enough flow back to tank, I would urge anyone that is having fuel problems or high fuel temps to pull the return line off and test it into the filler neck and what bothered me about this magical 14psi before fuel returns to tanks is 1. on my truck that is not right. 2 on my truck the only way to get to 14 was to restrict the return which defeats the object.

 

For the record.... this is on MY truck and I'm not suggesting for one minute that 5 to 7 psi is good on anyone elses truck, I just know it's good on mine 

[Tractorman]

On 5/25/2021 at 7:21 PM, Tractorman said:

First test = 3 cycles of bump start (approximately 25 seconds each time for three times - engine not running, lift pump pressure 14 psi) - Results were barely a trickle entering the bucket. 

 

Second test = start engine and let idle, fuel pressure at 12 psi - fuel immediately begins pouring into the bucket quickly covering the bottom.  I estimated about .3 gpm (about 18 gph)  Raised engine rpm to approximately 1800 rpm - flow visibly increased.  

 

@W-T, these are the results from the test on my truck from my previous post.  I have a background in hydraulic fluid power systems and to me the VP44 fuel system has to follow basic hydraulic principles regarding pressure and flow.  It is for these reasons I have never been particularly concerned about low lift pump pressure for the VP44 pump on my truck, especially since the replacement VP44 pump has the Bosch fixes already in place.  I expect that this 260,000 mile VP44 replacement is nearing the end of its life, and if it is, it has been a good life, but who knows?

 

As for heat soak on the PSG - what about the ECM that is bolted to the side of the engine block?  It has proven to be a reliable electronic device under similar heat soak conditions, but nobody seems concerned to the point of adding additional cooling.

 

W-T, I appreciate what you have brought to the forum and I like you style of writing.

 

- John

 

[JAG1]

John, could it be said then that having higher that 14 p.s.i. is a benefit at idle for helping with cooling? What happens at higher rpms when the VP44 is using more fuel and say you have 10 psi during a fuel pressure draw down when going over the long grade and towing? Does the return flow/ cooling diminish during those events because the overflow valve only opens when reaching 14/15 psi ?

 

Just asking not trying to contradict. 

[LorenS]

Why make the lift pump work to overcome the 14 PSID valve? If a guy put in an aftermarket back pressure regulator, he could also install a normally closed solenoid around that regulator and energize it only when running the lift pump in cool down mode. See sketch.

[Silverwolf2691]

Thats why i suggested the vent valve. Open from 0-5 psi for example, then closes above that. That leaves the check valve that is already there to take care of eveything else. No wiring (beyond making it run after shut down) no thinking about it. Problem is my company wouldnt make a single valve for a price that people would like. But we are proud of our quality and tolerancing and thats why our customers keep coming back.

 

Btw, @LorenS, nice job on the hydraulic schematic. 

Edited May 27, 2021 by Silverwolf2691

[Dieselfuture]

[Tractorman]

10 hours ago, JAG1 said:

John, could it be said then that having higher that 14 p.s.i. is a benefit at idle for helping with cooling?

 

I don't see how it could.  It is not the lift pump that pushes fuel over the 14 psi overflow valve.  The lift pump cannot push fuel through the fixed displacement internal vane pump whether the engine is running or not.  The lift pump only charges the inlet of the internal vane pump.  It is the internal vane pump that supplies the abundance of fuel immediately as soon as the engine is started. thus supplying a strong return flow of fuel to the fuel tank right away.  

 

Here is what we don't know about the internal vane pump:

 

*  displacement - cubic inches per revolution (volume of fuel being pumped at a specific engine rpm)

*  is the pressure regulator valve for the internal vane pump always in operation?  If so, what is the volume of fuel being returned to the suction side of the internal vane pump during various engine rpm's?

*  

 

Here is what we do know about the internal vane pump:

 

*  it is a fixed displacement pump which means the volume being pumped is directly proportional to engine rpm.

*  as soon as the engine is idling the internal vane pump is immediately displacing a specific volume of fuel.

*  we learned from Mopar-muscle, Apr 24, 2001's fuel return flow test that an idling engine produced 18 gph return fuel flow to the fuel tank.  This would mean that the internal vane pump is supplying at least 18 gph.  BUT, what we don't know is how much fuel is passing over the pressure regulator valve in the internal vane pump circuit?

 

10 hours ago, JAG1 said:

What happens at higher rpms when the VP44 is using more fuel and say you have 10 psi during a fuel pressure draw down when going over the long grade and towing? Does the return flow/ cooling diminish during those events because the overflow valve only opens when reaching 14/15 psi ?

 

The return fuel flow will significantly increase as engine rpm increases.  If engine rpm is raised from idle (800 rpm) to 2400 rpm, the internal vane pump will triple its volume (it has to because it is a fixed displacement pump).  The 14 psi overflow valve is in common with the outlet of the internal vane pump - not the outlet of the lift pump.   If the engine is running, fuel is being returned through 14 psi overflow valve.  Mopar-muscle, Apr 24, 2001 has shown us this:

 

DD2 , DD TTPM (True Torque Power Module)
FP volume
idle 11 psi 18gph

cruise 8 psi 24gph

WOT 2 psi 30gph


DD2 , TTPM , HOT PE ANY LEVEL
FP volume
idle 11 psi 18gph

cruise 8psi 24gph

WOT 0 psi 30gph

 

- John

[Silverwolf2691]

1 hour ago, Tractorman said:

It is not the lift pump that pushes fuel over the 14 psi overflow valve

The one next to the supply inlet? I thought that was the entire reason for the recommendation over the past what, nearly decade?, for the 14+ psi inlet number that MoparMan had discovered.. The supply goes right past the overflow valve.

 

The other thing is i cant imagine that vane pump pushing that much.. we wouldnt be able to run normal air dog or fass pumps. The air dog 220 is 220 gallons per hour not gallons per minute. 220 gph is about 3.5 gallons per minute. Other thing is the open area of the vane pump doesnt look very high capacity.

 

(I'd like to amend previous paragraph, its late and an interesting night at the fire dept monthly meeting/annual vote, i misread the flow figures from mopar-muscles post. Read gph as gpm... )

 

https://www.cumminsforum.com/threads/bosch-vp44-101.1839897/

 

Looking at some of these schematics, maybe we are both wrong because the first one shows the over flow valve is only on the return for the distributor needle valve... 

Edited May 28, 2021 by Silverwolf2691

[LorenS]

Aren't there TWO pressure reliefs, one internal for the vanee pump set at a higher PSI and relieves internal to the pump, and the external one that pops at 10-14 PSID and returns to the tank?

[Tractorman]

47 minutes ago, Silverwolf2691 said:

The one next to the supply inlet? I thought that was the entire reason for the recommendation over the past what, nearly decade?, for the 14+ psi inlet number that MoparMan had discovered..

 

It has been highly recommended, but I never have believed it is true for the reasons I have stated.  The fuel circuit is a series circuit.  The lift pump feeds directly into the inlet of the internal vane pump.  The internal vane pump fills the plunger chamber for the high pressure injection pump.  This explanation is simplistic, there is much more going on.  It is my understanding that the fuel solenoid cycles rapidly.  When it is de-energized, the fuel in the plunger chamber (which is fuel flow from the internal vane pump) is in common with the 14 psi overflow valve providing the fuel return flow.

 

The valve next to the supply inlet is not the overflow valve.  It is the pressure regulator for the internal vane pump.  See below.  Pay close attention to the directional arrows.

 

 

 

From Jimmy Jeeper:

 

And that brings us to the Overflow Valve (perhaps the simplest and most misunderstood piece in the VP44).The overflow valve is fed from a separate passageway in the distributor shaft but senses the actual pressure to which the plunger chamber is filled prior to being isolated from the accumulation chamber by the solenoid valve (prior to being pressurized by the high pressure pump). Any excess fuel above the overflow valve set point (about 14 PSI) is returned to the fuel tank by way of the Overflow Valve. The vane pump will always provide more than enough fuel to fill the plunger chamber, therefore there will always be flow back through the overflow valve and, therefore, always cooling flow through the VP44 as long as the engine is running and sufficient fuel volume is available at the vane pump inlet. By design, approximately 70% of the fuel provided by the vane pump will be returned to the fuel tank by the Overflow Valve. Some fuel is also returned to the tank from the injectors. The manual states that “A small amount of fuel is returned from the fuel injectors, while a large amount (about 70% of supplied fuel) is returned from the fuel injection pump”.

 

52 minutes ago, Silverwolf2691 said:

The other thing is i cant imagine that vane pump pushing that much.. we wouldnt be able to run normal air dog or fass pumps. The air dog 220 is 220 gallons per hour not gallons per minute. 220 gph is about 3.5 gallons per minute. Other thing is the open area of the vane pump doesnt look very high capacity.

 

From Jimmy Jeeper,

 

By design, approximately 70% of the fuel provided by the vane pump will be returned to the fuel tank by the Overflow Valve

 

If an idling engine returns 18 gph and that is 70% of the the internal vane pump flow, then the internal vane pump would be producing approximately 26 gph.  The flow would increase to about 78 gph at 2400 rpm. These are just round numbers.  Remember, it is unknown how much fuel is being pushed the internal vane pump regulator valve.  This would be well within the range of any FASS or Air Dog lift pumps.  

 

- John

[Haggar]

Guys,  remember the outlet check (the 14psi when FULLY OPEN)  is not fully closed at zero PSI.  It has a bleed through.  It is a variable restriction, but not a "check"  It will flow with 0.0 psi differential (ok you can;t have flow at zero differential it's in the definition, but think of the smallest differential you can imagine...).   Pull yours out and test it.

 

Hag

Edited May 28, 2021 by Haggar
flow at zero differential is impossible

[Mopar1973Man]

Correct this is why I suggest 14 to 20 PSI. Below 14 PSI is starts closing then by 10 PSI the overflow is closed. All extra cooling and luring is gone below 10 PSI.

[Dieselfuture]

2 hours ago, Mopar1973Man said:

Correct this is why I suggest 14 to 20 PSI. Below 14 PSI is starts closing then by 10 PSI the overflow is closed. All extra cooling and luring is gone below 10 PSI.

I agree but I think the debate now is what is pushing it open the lift pump or the internal vane pump, and if it is internal pump that pushes 300psi then I'm confused why bother putting in a 14psi valve  I'm trying guys give me a break

[JAG1]

Thank you Tractorman for going over that again. It helped.  

[LorenS]

Having never taken one of these apart myself and the videos not stating directly one way or the other, I have to ask the most basic of questions.

 

Referring to the photo with the zip-tie, if a guy were to remove the 14 PSID regulator and look in the hole, would he see the zip-tie? Does the regulator valve tie into that passageway or not? From photos it looks like it has to, but the pretty cartoon picture indicates it does not.

 

I have enough leaks on my truck I'm not about to take my apart any time soon. And since my wife and I bought a new house I'm really in need of my truck (and time) right now!

[Silverwolf2691]

9 minutes ago, LorenS said:

Referring to the photo with the zip-tie, if a guy were to remove the 14 PSID regulator and look in the hole, would he see the zip-tie? Does the regulator valve tie into that passageway or not? From photos it looks like it has to, but the pretty cartoon picture indicates it does not.

 

@Mopar1973Man, when you took the pump apart, did you see the ziptie in the banjo bolt hole while setting up that photo? 

 

I want to take one of these into work and hook it up to one of our test stands and see what happens when you spin the input or just see what happens in general

[wil440]

I'm absolutly gobsmacked.... what part of 5 to 7 psi at idle with good return flow to tank don't people get AND fuel temps sub 100f. tested.... tested ..... tested and tested some more, this is not thery looking at a picture this is tested

 

Go ahead and perpetuate the 14psi "before fuel is returned to tank" and "no cooling" I know from testing that is absolute rubbish, hands up who has checked with the return into either a bucket or the filler neck, if you've done neither then you don't know for sure, i've done the latter over at least a day changing lines, changing where the reg is, changing filters, changing everything I can think of.... same conclusion, same result, 5 to 7 at idle and way more than enough back to tank and my fuel temps back that right up. Go ahead and test it is really easy especially as like my truck the return was fubared

 

one other to bear in mind here..... the VP44 pump has been used extensively here in the UK and Europe, parts seem to be cheaper here..... BUT while it's reputation is not perfect it is in now way as bad as in the USA and no one here bothers a rats *** about fuel temps, or lift pumps, or fuel level..... but it is not bolted onto a million mile engine either

[LorenS]

I drove 300 miles Wednesday, only shutting the engine off for a few minutes to refuel. Fuel temp reached 150 ⁰F with 17+ PSI. Air temp less than 80 ⁰F.  No trailer, 70 MPH.

 

I'll mention I also achieved a fuel mileage record on that tank, 20.9 MPG! The day before was another 300 mile day mostly highway and rural roads.

 

My fuel still returns to the basket, though.

[wil440]

48 minutes ago, LorenS said:

I drove 300 miles Wednesday, only shutting the engine off for a few minutes to refuel. Fuel temp reached 150 ⁰F with 17+ PSI. Air temp less than 80 ⁰F.  No trailer, 70 MPH.

 

I'll mention I also achieved a fuel mileage record on that tank, 20.9 MPG! The day before was another 300 mile day mostly highway and rural roads.

 

My fuel still returns to the basket, though.

Air temp is around 26c which here is a good summer day, I have never seen 150f for fuel temps, I think fuel pressure is a bit of a waste of time measuring as it is just a measure of restriction, I can build some serious fuel pressure on my truck IF I restrict the return line with brake line calipers (brake line seal tool)

Actually your truck and my truck couldn't be further apart on fuel pressure and fuel temperature, my FP at idle is 5 to 7, yes at say 2k my FP is closer to 20psi but as I have said at 5 to 7 I HAVE tested return flow and while I didn't measure it I can say I'm happy with it 

[dripley]

Mine has run just fine for a decade with its current set up. I did base it on the 14 psi minimum. I do know some members here dont subscribe to that and thats fine with me. We all get to make our own choices. I do know prior to this set up I was having trouble with some bucking and dead pedal issues. This on the in tank pump that Dodge blessed me with. After taking the truck to a reputable shop and paying what I considered  a fair price for there time, the only thing they could find was near 0 psi of FP under heavy throttle and about 4 psi at idle. as I remember. So I added a booster pump from BD diesel and the problem went away.  I had no pressure gauge so how much it raised I dont know. Just know it worked.  Nor do I have clue of fuel temps.

It did make a good difference for me and I am good with my set up. If it is working fine with lower psi for anyone, run with it.