VP44 Injection Pump Teardown - How it Works

[Dieselfuture]

6 hours ago, W-T said:

What if there was a timed circuit ( a simple 555 chip) that allowed the fuel pump (lift pump) to continue to run for a period of time to skirt away heat "after shut down" with incremental "run time" being manually adjustable?   

I believe I've heard someone talking about before where if the motor is not running the fuel will not get pushed passed a certain spot in vp. Vp needs to be turning for fuel to go through. That's what I heard, not sure how true that is. 

[JAG1]

Interesting topic. Someone please correct me..... the circuit board on top of the VP is called 'ECU' or is it 'PSU'? Thank you in advance

[Dieselfuture]

11 minutes ago, JAG1 said:

Interesting topic. Someone please correct me..... the circuit board on top of the VP is called 'ECU' or is it 'PSU'? Thank you in advance

PSG

[Silverwolf2691]

1 hour ago, Dieselfuture said:

I believe I've heard someone talking about before where if the motor is not running the fuel will not get pushed passed a certain spot in vp. Vp needs to be turning for fuel to go through. That's what I heard, not sure how true that is. 

 

I have hard the same thing.. if i had to guess its the vane pump. No engine turning, no fuel moving (usually)

[Tractorman]

2 hours ago, Dieselfuture said:

9 hours ago, W-T said:

What if there was a timed circuit ( a simple 555 chip) that allowed the fuel pump (lift pump) to continue to run for a period of time to skirt away heat "after shut down" with incremental "run time" being manually adjustable?   

I believe I've heard someone talking about before where if the motor is not running the fuel will not get pushed passed a certain spot in vp. Vp needs to be turning for fuel to go through. That's what I heard, not sure how true that is

 

I am a firm believer that this is true.  The lift pump provides a positive pressure to the inlet of the fixed displacement vane inside the VP44 injection pump.  Fluid cannot be pushed through a stopped fixed displacement pump.  The best you can get is internal leakage that will dribble out some return fuel - certainly not enough for cooling. 

 

Just last week I installed a return line tee into the filler hose for better cooling of returned fuel (which was a success) I believe this modification will provide adequate cooling for the VP44 under all driving conditions.  Before I completed the installation I performed two return flow tests into a five gallon bucket.  My lift pump is a frame mounted FASS DRP-02.  Not sure what the output is, but I know it is less than 100 gph. 

 

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.  

 

My truck currently has logged 355,000 miles - 87,000 miles on a warrantied VP44 and lift pump, and now 265,000 miles on the replaced VP44.  This VP44 has never seen 14 psi ever at its inlet (lift pump pressure) with engine running.  Most of the time it is 10 psi or less.  This does not concern me as I know that there is always a positive pressure.

 

I have posted the following copy of a post before, clearly showing the direct correlation between internal vane pump output and engine rpm.  This was posted on a different site by Mopar-muscle, Apr 24, 2001, before I even owned my truck.

 

Test # 1

well some of you guys ain't gonna like this , especially those led to believe (and those that believe it) ... the bigger is a MUST theory .

spent a couple minutes running some tests with a DIGITAL/mechnical flow meter and a MECHNICAL fuel pressure gauge , items under test ... 2000 RAM , DD2's , DD TTPM on level 2 (??) and a HOT PE , ( all levels tested the same at WOT)factory pickup , factory lift pump , factory fuel filter housing unmodified , all banjo bolts intact and unmodified except the banjo to the input of the lift pump is replaced with a 90* swept areoquip type -6AN hose end , the bolt at the lift pump had the schrader cut off and drilled and tapped to a 1/8 npt ( for the gauge) and the banjo fittings between the lift pump and the fitler housing have been drilled to 9/32nd . again all banjo bolts are not drilled out as i have on my ram ( test conducted on the DTT RAM ) .

we installed ( LaserBob is helping me and getting #2 fuel poured on his head ) a Sonnex digital flow meter ( inside ID is 5/16") in the return line back to the tank , cut in right at the trans crossmember . gph numbers are fuel returned to the tank .


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


yes you read that correctly , fuel pressure went to 0 and the fuel volume back to the tank did not change from WOT with 2 psi . the truck did NOT stumble , buck , spit , fart , fall on it's face , nothing , ran like all heck at 0 psi , i will note , my truck ran the same at 0 psi with the DD3's , EZ and a HOT PE .
 

 

- John

Edited May 26, 2021 by Tractorman
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[Dieselfuture]

I think we're splitting hair here. Most of people can get 250,000 miles out of vp as long as lift pump still supplies fuel, not saying 17-18 psi is not ideal just saying it seems that there are plenty of people that got that many miles even with stock lift pumps as long as they work. 250k is good enough for me for vp, sure it be nice to get 500 but I'm ok with 250ish. 

[MikeH]

I believe the latest Revision pumps are fairly reliable daily drivers with enough fuel pressure and lubrication added. If you're hell bent on horse power just have the thing P-Pumped and be done with it. The VP44 was just a stop-gap pump between the P7100 and Common Rail. Had Bosch got the manufacturing right at the start (deburring, diaphragm and PSG solder issues) and Dodge started out with a decent in-tank fuel pump (~15psi) we probably wouldn't be having these conversations. 

As to the heat issue there's two things I do on a regular basis. First is to keep the tank full whenever possible. Especially in the summer a full tank becomes a giant heat sink. Also, filling up more often cools the fuel already in the tank and the process starts all over.

The other thing you can do is to just crack the hood after a long hot drive and let the heat out. I don't do this if I'm running over to Home Depot and back. But on long trips where the engine is fully up to temp that hood's coming open when I stop. You have to feel for the electronics in that VP, what with a red hot cast iron engine on one side, surrounded by two large batteries and completely covered by the APPS bellcrank it might as well be in an oven, roasting 'til the engine bay cools off. With the hood open not only is hot air going out the top but cool air is being fed up from the ground. Engineers call this a Stack or Chimney Effect. Will this save you injection pump? I don't know...but it makes me feel like I'm doing something to address the over heating issue.

Just a couple of ideas to think about. They're very low tech and require no additional costs or effort.  

[dripley]

On the other side my last VP went 275k. My fuel pressure is between 15 to 20 psi. Both return lines are in the fuel basket and I fill up mostly around the the low fuel light illuminating and below if on a long highway run. When just around town I still only fill up when below a quarter tank. I have about 40k on this new VP and it is on the same diet. It would seem to me there is still more than one way to skin this cat or should I say pluck the chicken.

[Tractorman]

27 minutes ago, MikeH said:

Had Bosch got the manufacturing right at the start (deburring, diaphragm and PSG solder issues) and Dodge started out with a decent in-tank fuel pump (~15psi) we probably wouldn't be having these conversations. 

 

I absolutely agree with this - and don't forget the timing piston, too.  I think that blaming lift pump pressure was an easy out for Bosch while quietly fixing the afore mentioned issues without fanfare.  At least they fixed them.

 

- John

[wil440]

3 hours ago, Tractorman said:

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.  

That is exactly the result I saw when I was messing about with my truck trying to find out why I had 5 to 7 ish psi at idle, I also ran a temp hose into the filler neck to test, plenty of flow to the point of I don't bother about 5 to 7psi at idle anymore, my return fuel still goes into the basket ( made the filler neck T but haven't fitted it yet)  fuel temps never go to 120F

[Mopar1973Man]

I can say without a doubt I found a gent that has managed in increasing the VP44 volume and capacity. We've been talking for a awhile and made a beta test pump. I can't remember the volume per stroke but it's got more than a dragon fire pump.

[JAG1]

10 hours ago, Tractorman said:

 

I absolutely agree with this - and don't forget the timing piston, too.  I think that blaming lift pump pressure was an easy out for Bosch while quietly fixing the afore mentioned issues without fanfare.  At least they fixed them.

 

- John

Tractorman, I quoted you above John only to get your attention, are you saying that cooling/ return flow increased in gpm when you ran the return line into the filler neck 'T'? And therefore discovered less restriction in flow? Thank you in advance. An important aspect to this discussion if so.

[Tractorman]

21 minutes ago, JAG1 said:

Tractorman, I quoted you above John only to get your attention, are you saying that cooling/ return flow increased in gpm when you ran the return line into the filler neck 'T'?

 

Not at all.  The return flow would remain the same.  I am saying that the return flow is dependent on the internal vane pump flowing fuel over the 14 psi overflow valve - not the lift pump operation.

Edited May 26, 2021 by Tractorman
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[Me78569]

20 hours ago, Silverwolf2691 said:

and here I am trying to figure out why the vp44 cant fuel for high rpm power.. most people say that the plungers cant fill fast enough, but they are supplied with 100 to 300 psi of fuel inside so I dont think that is it, at least not totally.. Then theres what @Me78569 found with the quadzilla testing, that the ecu is putting out a full stop runaway protection signal to the vp44 after 3500 rpm. I swear theres a market for something similar to the smarty but able to futz with other things besides fuel and timing. Turn off or raise overboost code limit, raise runaway protection rpm, stuff like that.. But if I had to guess Smarty has a monopoly on the obdII flash style tuning. Meaning cease and desist sales of said fictional programmer.. Sorry, slight sore spot from the piles of limits that people say about the vp44.. Alright off the soap box..

 

 

 

the issue with rotary pumps is physics say that the faster you spin it the harder it is to push the fluid to the center.   

 

Rotary plunger pumps lose their ablity to pump at high RPMS.   yes the ecm freaks out above 3500 rpm, but that is not the whole story either.   How much would it help to truly raise the rev limiter in the ECM to 5k? I dunno, but the pump does start get inefficent at high RPMS.

[W-T]

19 hours ago, Silverwolf2691 said:

 

 

I would say it would be better to have a second return port above the larger opening where the timing tone wheel is. I say this because the ofv is only shortly down the inlet so only half of the board would see moving fuel for cooling. I'm referencing a few photos of the vp44 disassembly article that @Mopar1973Man did.. how to achieve this i dont know off hand.. but i might have an idea.. 

 

My work has a vent valve. Essentially its a poppet with the spring on the down stream side keeping the poppet off the seat. When the pressure gets high enough the poppet closes and blocks off the flow. If it was set up to shut off above say 20 psi you could flow after shutdown then when it builds pressure in the timing chamber after startup (if im understanding/remembering how it works correctly) it would shut off flow and keep pressure in the vp44. On shut down the valve opens and allows flow for cooling.

This is interesting @Silverwolf2691 and I need to learn more about what you've brought here. This could be a glimmer of hope.

 

16 hours ago, Dieselfuture said:

I believe I've heard someone talking about before where if the motor is not running the fuel will not get pushed passed a certain spot in vp. Vp needs to be turning for fuel to go through. That's what I heard, not sure how true that is. 

Indeed...I agree the pump at rest will not allow full flow-through and the static tests run by several members here are quite revealing with dismal flow rates being so minimal.

 

Again, thank you all for the quality feed-back on an old subject matter. I'm sure we'd all enjoy an additional "cool-down" procedure that may increase longevity and I fully agree with @Dieselfuture that achieving 200K miles or better is certainly acceptable, along with @dripleyreporting better than 275K...gosh I guess I maybe asking for too much.

 

But, again there is no harm in attempting to find a method where post shut down of the engine would allow for continuous flow of fuel to aid in abating "heat soak" conditions that we all agree does exist...

 

Too bad this was not a consideration by Bosch in the initial design and I only mention this by guessing how many VP44's were replaced due to PSG failures that could have been avoided "if" a simple post-run cooling flow had been incorporated to begin with. 

 

Being involved with this site containing other like minded people researching "what if scenarios" is quality therapy for me. I complement all of you and your wonderful affliction of "Excessive Compulsive Disorder" in the pursuit of technical excellence... it gives me a feeling of being at home. 

 

None the less...I still wish to discover an excellent video presentation (preferably in English) that really shows the exact fluid flow characteristics within this pump. Having worked in the industrial pump industry for many years I understand the proprietary cautions of Bosh NOT wanting full disclosure of the working structure. I also experienced such disclosure cautions in two different companies even though protection clauses were in place. (China is a problem)

 

Again, Thank You all for the added information.

Cheers,

W-T

 

     

[Silverwolf2691]

Disassembled A Bosch Vp44 Injection Pump - Page 3 - 2nd Generation Dodge 24 Valve Powertrain - Mopar1973Man's Dodge Cummins Forum

 

^ The article/forum thread I was referencing earlier 

 

 

@W-T, this is what I was referencing in my post about the extra return port. (would have the port in the top side (engine side) of the skinny and deep chamber, that way there is flow across the whole psg) Supply is the right boss and ofv is the left boss. Where the zip tie is coming out of doesn't seem to be closed off (via psg) to the area below it in the skinny and deep chamber. But it seems like there would be no flow circulating in that area because the ofv would bleed any extra flow and pressure off before making it into that area. Essentially making a deadheaded area. I just don't know what pressure this is actually at, whether its at lift pump (~14 psi) or vane pump pressure (100-300 psi). 

 

I'm just going to put this here.. I could be totally wrong about this.. I only know what I know due to searching on the web, looking at the disassembly thread, and watching the YouTube video I posted earlier. If I am wrong, I apologize in advance and am willing to be corrected.

 

@Me78569, taking what you said into consideration as well, I just feel like the inlet port and the vane pump are limiting factors.. we have a 3/8-1/2 inch line and we feed all that fuel into a 6mm (I'm guessing) hole in an m10 threaded banjo bolt adapter that goes into the pump. There's only so much that is gonna be pushed through that small of a hole. The vane pump also moves what visually looks like a small amount of fuel. The smaller cousin of this is a vp30, its a 4 cylinder pump instead of 6 and used in the UK. Those have been tuned for 4-6k rpm (i think) by the tuners across the pond. However they are used on smaller engines so that plays into everything as well.

 

IDK, I'm just frustrated that the vp44 is just passed over with everyone just saying "..the vp44 is just going to die on you and leave you stranded and cant make power. Just ppump it.." my brother has a ppumped 24v that he bought that way and yeah the pump is turned up a bit and has some size bigger injectors than stock, but if its below 40°f outside it doesn't like to start, even cycling the grid heaters. mine will only start protesting if its below 10°f and no grid heaters, even then its a slight stumble and then full running. My truck is also a lot more drivable in the rich parts of the town I live in because I can turn my power down, my brother has to drive with an egg under his foot to not cloud everything in soot.

 

 There feels like there could be more potential left in the pump, but I'm sure it was given up on due to lack of interest and/or funding or client base.. 

 

Jeez im starting to sound like a rotary (Mazda) owner.. from factory tuned to a razors edge. But lack of care and knowledge on the owners part has caused them a lot of problems. The diehard guys are looking for more power and it essentially boils down to: bolt ons; max of like 15-20hp gain. [wire tap tuner] Want more? well turbo or supercharge it, but your engine life just got cut by a significant amount (greater than or equal to like 50% or something along those lines) [Monster pump mike vp44] . After that it becomes make your own billet rotary motor [the never been made, to my knowledge, billet vp44].. I wanted a Mazda rx-8 when I was younger, research yielded that my 19 year old butt couldn't afford it if it popped a motor.

Edited May 26, 2021 by Silverwolf2691

[W-T]

Now this is revealing...

Am I wrong to assume the fuel in "feed-boss" is flowing fuel into the chamber directly under the PSG at the level of pressure provided by the lift pump?

 

In reference to @Silverwolf2691 supplied photo (with zip-tie) it appears fresh fuel first enters this chamber, fills and then exits (follow the zip-tie) to the tone-ring chamber.

This flow then quenches the entire VP44 pump body for pressure manipulation.

 

 

This photo provided by @Mopar1973Man verifies the feed aspects.

 

In my experience of changing a fuel filter (Air Dog frame mounted) I always remove my trigger lines from the harness that originally provided DC to the factory lift-pump configuration. I use that trigger line to power my relay and provide PDC, DC to my Air Dog in the standard mode of operation. Changing my fuel filter I take a pair of alligator clip-leads and directly power up my relay closure to force the Air Dog into constant run mode. This fills my new fuel filter and burps the air from the flow-path and alleviates all hydraulic fuel/air issues prior to actually starting the engine. 

 

I've done this for years and the method is flawless. My Cummins starts on first key closure every time.

 

My observations of the "time element" that it takes the Air Dog to purge the system following a filter change is not more than one minuet maximum. I've actually allowed this configuration to static run for as much as 5 minuets just to see if my water separator has any water to glean due to long periods of none operation and alleviate the possibility of condensation occurring in my tank. Yes, I am also observing my mechanical fuel pressure gauge holding a level of 17 to 18 PSI during this event. 

 

The volume provide by this Air Dog is substantial and is plumbed through large inner diameter tubing to feed the VP44 directly. The "air separator" configuration of the Air Dog is plumbed back into the factory fuel fill tube via the Air Dog supplied splice-in manifold. Yes, removing the fuel-fill cap you can hear copious amounts of fuel-flow being fed back to the tank.

 

I also have the "draw-straw" modification configured as per @Mopar1973Manalong with modification of the "fuel-return" basket within the tank. Yes, I avoided allowing "hot" fuel to be redrawn into the system. This aspect is just common sense...

 

I have NOT experimented by measuring the volume of fuel being returned to the tank as others have shared in this running thread. I bring this forward ONLY because of my experience of "dead head" priming or purging the system after a fuel filter change out.

 

With the experienced examples being shared here, I'm quite puzzled to read about the dismal minimums of fuel being visually returned to a catch-bucket.

 

Again, I'm thinking out loud here...

 

In viewing the photo above from @Silverwolf2691 with the very revealing zip-tie flow path and countless discussions of the functional aspects of the "OFV" over-flow-valve and it's inherent properties as it functions... I must ask how the return in an experimental "open bucket" return flow be so minimal?

 

I admit, I've never pulled my return line and force activated my lift-pump to make such an observation in a "no run" scenario but, the simple empty fuel filter procedure I use has lead me to believe the feed through volume has merit. My intuition with a pump sinking nearly 8 amps with a factory rating of 100 GPH holding 18 PSI is substantial.

 

Simple math shows me a flow rate using Air Dog spec's of 100 GPH to be 1.666 gallons per minuet. That's enough to make a real mess on the shop floor if one was not paying attention!

 

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? 

 

Further more, all the "old time" data floating around being acknowledged as Biblical scripture that "there is NO flow through" when the VP44 is not in running mode hence, no fuel circulation.

 

With the photo @Silverwolf2691supplied, I must return to my initial exuberance of "the possibility" being valid. Previous shared observations causes me to question the driven PSI levels of the given lift pump and the operational aspects of the over flow valve?

 

I'll dirty the water further, these aftermarket electro-machanical lift pumps do require current to operate properly, at 10 amps nominally and a distance of 8 to 10 feet away assuming frame mount configuration voltage drop due to I*R losses must be considered. Prudent selection for NO error would be #10 gage stranded copper wire. This pays off well for those of you in colder environments during winter conditions.

 

I'm back to considering a "timed post run DC controller" to allow flow and battle "heat soak" syndrome.

 

I know I've not won favor with the mechanical fuel pump crowed however; don't throw away your old Carter lift pumps...they too provide a purpose in this possible venture.

 

Cheers,

W-T   

 

             

 

 

 

   

[Dieselfuture]

4 hours ago, Silverwolf2691 said:

Jeez im starting to sound like a rotary (Mazda) owner..

Nothing wrong with that  when I was in my 20s I had an rx7 1993 coolest car I've ever owned. Got it slightly racked in the front for a really good price, did all the repairs myself then I was a little hard on it and blew one of the rotors. Took the engine out it was surprised how small it was tore it all apart to realize I wasn't going to put it back together and it needed a lot of machine work. So I sent it down to Atkins rotary and had them put bigger Apex seals and do some race porting on it, then I had to get a stand-alone computer and program it to that engine, it was a fun little car. I was planning on putting much bigger injectors in and turbo on it but life changed and it got sold, it's still ran pretty hard with the original twin turbos that I rebuilt.

 

https://youtu.be/RVo4hKoBWe0

 

https://youtu.be/H7QDdxxOqyo

 

[Great work!]

W-T,  blow up that last pic. Right above the red letter 'd' there is a port plug ( ball thing) where the zip tie goes in the port is drilled all the way to that port plug from there it is drilled straight down and feeds the vane pump. The vane pump excess gets returned back to vane pump input NOT the tank. The leakage / lube for the rotor goes to the back of the rotor, some fuel also gets past the end of the spill valve and cools the solenoid coil all that fuel gets returned to the tank. So when not running there is a lot of restrictions  between the inlet and overflow.

[Silverwolf2691]

@Dieselfuture, nice rx7. And 12s @ 112 mph is nothing to sneeze at. Usually tuner/imports i dont like because of the fart cans most use for the exhaust. But rotarys (especially with a race port or bridge port) and neon srt4s get an exception in my book. Both just sound awesome. 

 

@W-T, I dont know why but the forum "sentence" on my post was supposed to be a link with a whole bunch of teardown photos but i copied the address and no hyperlink.. 

 

Man the reality check of forum posting is a bit wierd.. its 10p eastern at time of posting but for a bunch of you guys on mountain (8p) or pacific time (7p) are just sitting down to dinner, finishing dinner, or what not.