VP44 Injection Pump Teardown - How it Works

[MikeH]

Everything you wanted to know about the VP44 Injection Pump but were afraid to ask. I don't know if these guys do rebuilds or what but he knows his way around the pump: 

 

[W-T]

Nice contribution @MikeHI don't know who these fellows are but, it's nice to see a tear-down presentation at this level.

 

This pump is certainly a dual stage series configuration where the vane-pump is a continuous positive displacement of volume that feeds the piston(s) "single-action" displacement for increased pressure delivery. Both operating in series and operating like an amplifier to increase pressure as required. The output, being small pistons, would not carry volume however; the static pressure increase would be substantial compared to a single stage vane pump running in an open ended configuration. It's the capacitance or volume of the first stage providing copious amounts of fuel to allow the second stage to deliver the peak-punch or injection interval that is required and leaving the additional unused fuel as a coolant transfer medium. 

 

This brings me to the question of the "slightly glossed over" explanation of the "diaphragm" in the flow path?

 

I would be interested in seeing a visual presentation of the liquid flow within the pump under normal operation to clarify the properties or action of this diaphragm.

 

I've assumed this component is operating as a buffer stage between the higher pressure piston action and unused fuel (at high pressure) following an injection event being returned to follow the next event. In design, fluid dynamics become messy when one stage is interrupted or back-fed "positive feed-back" from a down stream source. The eddy currents could cause havoc in a high pressure closed system resulting in undesirable dynamic hydraulic phenomena. 

 

This video presentation stipulated the diaphragm is operating as a buffer stage between the high pressure output and the driver stage (vane pump) and this realization has caused questions to my initial understanding.

 

Good stuff MikeH... it's fun to ponder such designs. Gosh this pump is certainly sophisticated!

 

BTW...seeing the working components and the minute travel and physical changes during the cycling actions really allows an appreciation for clean fuel disciplines and additional lubricity in our 2nd Gen platforms. 

[MikeH]

"seeing the working components and the minute travel and physical changes during the cycling actions really allows an appreciation for clean fuel disciplines and additional lubricity in our 2nd Gen platforms"  W-T...couldn't agree more. As he mentioned in the YouTube clip everything is metal to metal contact (no bushings, bearings etc) and without engine oil as a lube you're totally dependent on the fuel for lubrication. We already knew that but looking at the inner workings really brought home the need for clean well lubricated fuel.

I've always gone a little overboard on additives especially those with the best lubricating qualities. I now mix my own but Opti-Lube Summer Blend is the key component.

Safe travels!

[Great work!]

The diaphragm is held in the center with a snap ring the outer edge of it has an o ring. The outer portion 'flutters' as the high pressure fuel gets spilled back toward the chamber that the diaphragm encloses. The injection plungers are still moving when the spill valve opens at the end of injection  so the pressure pulse is absorbed  by the diaphragm chamber.

[Mopar1973Man]

Just remember the diaphragm is not rubber like early versions. The current version uses a steel disc.

[JAG1]

The diaphragm divides the pressures between the vane pump and return fuel as per the presentation, he states damage is possible when return pressure becomes too high not the lift pump pressure, also stating, is only a possibility and needing further investigation. My thoughts often need correction but, aren't the vane pump and return pressures similar? Or at least often noted in the lower end scale being in the 14 to 20 psi scale?

[Great work!]

The vane pump output has a regulator it goes from about 100 psi at idle to 300 psi at full speed. Saw it in a Spanish youtube once. The diaphragm  can crack from metal fatigue and the outer o ring wears from oscillating back and forth in the bore. The Vane pump feeds the inside of the injection plungers and causes them to move outward and follow the cam ring (no springs). The outer part of the plungers are exposed to lift pump pressures. So low vane pump pressure during cranking on one  side vs high lift pump pressure on the other plus a leaking diaphragm causes the plungers to not follow the cam ring which causes hard starting.

[JAG1]

You can certainly seen a strong need for lubrication in this design. The new ULSD is not going to meet these needs and I'm not sure about Biodiesel meeting lubricity requirements when I've not seen what the score values are for bio.

 

I am still currently using 2 cycle oil in ea tank weather bio or not. In fact going a bit heavier doses these days can't hurt.

[MikeH]

11 minutes ago, JAG1 said:

You can certainly seen a strong need for lubrication in this design. The new ULSD is not going to meet these needs and I'm not sure about Biodiesel meeting lubricity requirements when I've not seen what the score values are for bio.

 

I am still currently using 2 cycle oil in ea tank weather bio or not. In fact going a bit heavier doses these days can't hurt.

As little as 2% Biodiesel will supply all the lubrication you need. This is a study done years ago if you haven't seen it:  https://www.jatonkam35s.com/DeuceTechnicalManuals/Diesel_fuel_additive_test.pdf

My concern is that "new guy" at the fueling docks forgetting to put the additives in the tanker truck and you end up running straight ULSD. I'm sure it rarely happens but people make mistakes sometimes. That could be really bad news for the VP44 so I always toss in enough additive to make sure I'm covered. Overkill I'm sure but my 20 year old pickup with a 14 year old injection pump is still running down the road.

[JAG1]

Thank you Mike H., Interesting study. I remember another test lab result Michael Nelson provided years ago had 2 stroke higher up on the list. 

 

Great Work, thank you for your valued information to this important thread. 

[Mopar1973Man]

4 hours ago, MikeH said:

As little as 2% Biodiesel will supply all the lubrication you need.

If you Idaho like I am there is no bio-diesel available. Now if I travel 125 miles I can get B5 in Oregon at a much steeper price. 

[MikeH]

1 hour ago, Mopar1973Man said:

If you Idaho like I am there is no bio-diesel available. Now if I travel 125 miles I can get B5 in Oregon at a much steeper price. 

Mike, I've heard but can't confirm that some biodiesel gets included in almost all diesel fuel delivered in the US. Stations like the Stinker stores here in the NW used to advertise B5 (or some %) for sale but they no longer say that. Haven't figured out if that's because they no longer sell biodiesel or because everyone's adding it and not much of an advertising gimmick anymore. Got this from Car & Driver.com: "According to Edmunds, its production has increased from 25 million gallons in 2005 to 1.7 billion gallons in 2013. Today, biodiesel is blended at a rate of 5% or less into almost all the diesel fuel sold in the United States".

It makes sense in that even 2% bio would take care of all lubricity issues in raw ULSD. Just can't confirm that for the fuel here in SW Idaho. To be on the safe side I'm going to keep using a diesel fuel additive. 

[dripley]

The Loves travel center I built a few years ago had their own bio tank in the on site tank farm and they mixed it on site. I used to buy their fuel for the bio but their prices on diesel are 15% higher than other places. Some of those have a sticker on the pump that says  MAY contain 5% or less of bio. I like the stuff and the truck does to. But until I know what is in it I will add the 2 stroke.

[Blueox01]

38 minutes ago, dripley said:

The Loves travel center I built a few years ago had their own bio tank in the on site tank farm and they mixed it on site. I used to buy their fuel for the bio but their prices on diesel are 15% higher than other places. Some of those have a sticker on the pump that says  MAY contain 5% or less of bio. I like the stuff and the truck does to. But until I know what is in it I will add the 2 stroke.

I have a friend that is now building the freezers/cooler in some of new love's Truck stops.

[Silverwolf2691]

On 5/22/2021 at 6:18 PM, W-T said:

I would be interested in seeing a visual presentation of the liquid flow within the pump under normal operation to clarify the properties or action of this diaphragm

 

I might be able to help slightly with that..

Fair warning, 25 mins long and not in english but the auto translate for closed captions works well enough.  

 

 

[W-T]

Hey @Silverwolf2691 thank you, I wish I had the skill in Spanish but, I can tell this presentation is certainly worth while.

 

I know many of us have combed over the internet for many years gleaning as much information as possible regarding the VP44. My general observation in an overall sense leads me to believe the Europeans and Latin countries appear to have a more in depth understanding of this pump. 

 

I'm not saying our diesel enthusiasts here state side aren't up to the task but, the real meat and potatoes backyard mechanics overseas are certainly resourceful. Perhaps, the financial challenge they face in regard to "replacing" a VP44 in questionable condition must be carefully thought out prior to laying out the cash. I'm not fond of the cost myself but, when I see a Russian fellow tearing into a circuit board on a VP44 and diligently attempting repair (some procedures are brutal) my guess is, the poor guy has to due so because he can't afford the financial burden of simple replacement and I certainly applaud his focused dedication.

 

Jokingly, I must add that my wife knows nothing about diesels but, she's watched my antics over the years and when she hears the term " VP44" she arms herself with a frying pan and I'm looking for the nearest exit...

 

This entire VP44 subject matter has loomed large for over twenty years and I'm sure many experienced 2nd Gen enthusiasts have read volumes on this subject and many are possibly bored with the topic however; being that this community is an inquisitive gathering of like minded people I appreciate the continued banter. Finding @MikeH bringing forth a good video and @Great work!adding additional observations in "function" tells me good minds are still pondering the subject.

 

Why am I jumping on this band wagon? Because I want to know the exact fluid-flow characteristics within this pump and possibly find a reasonable method to address longevity.

 

Contributions over the years are helpful and the work of @Mopar1973Manindoctrinating all of us to fully adopting the "lubricity" aspects of fuels available that changed shortly after many of us purchased these trucks made a key mark in overall longevity. I believe all of the 2nd Gen owners "who are in the know" dope their fuel accordingly.

 

So...I appreciate the contributions coming forth 20 years down the line and I must admit, the methods are certainly much more sophisticated and worthy considering the time it took to achieve worth while results.

 

I'll stop being cryptic, I wish to find a method to allow fuel to circulate for a period of time after shutdown (hot condition) that would partially alleviate the "heat soak" for the electronics on the VP44

 

I'm just think out loud here...

 

I know of the aftermarket "fans" blowing air on the VP44 housing...this is old subject matter and isn't my pursuit. I can think of many diesel enthusiasts going back 20 years who have partaken in such topics on other websites where such projects were being bantered about. I guess I'm just hoping to draw out the "thinking minds" who may have additional information and experience along this topic. Heat is our enemy in nearly all devices we work with or operate...I think there is room for advancement here. 

 

The manual transmissions have aftermarket "coolers" that allow additional fluid to be incorporated in overall volume...automatic transmissions have deeper pans to allow an additional volume of fluid, both of these examples contribute to additional cooling. 

 

The chamber on top of the VP44 that is filled with circulating fuel directly below the circuit board to skirt away heat during run time is already there.

 

What if there were and "extension" housing sandwiched between the circuit board and the VP44 body to allow for additional fluid volume?

 

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?   

 

What if this hypothetical "extension housing" was equipped with "thermo-electric Pelter Junction" devices to be activated on a timed basis to function for a period of time after the "circulation" period had timed out? This simple aspect would assure standing fluid within the wetted chamber would drop "heat soak" static temperature an additional 10F.

 

Take a look guys and gals..."Pelter Junctions" are very inexpensive low current solid state wafers...the efficiency of these trick devices have advanced dramatically due to the field advancement of the photovoltaic panels.

 

Sorry for my exuberance in theoretical possibilities, I do not mean to pontificate, I wish to stir the senses of diesel enthusiasts and gain knowledge from them.

 

@Haggar, @KATOOM...do you think this could be a worthy investment of time?

 

 

 

 

 

 

 

 

[JAG1]

I know Blue Chip Diesel was, awhile back, looking for ways to isolate the PSU circuit board away from residual heat after shut down but, found no way to do that. W-T's idea of an extension is a good one since the wire harness can remain inside the chamber. Added fuel volume and flow after shut down is ideal and perhaps an adaptable extension can be simple to add without interruption to the wires inside. 

 

I currently provide heavy doses of 2 stoke to each tank weather Bio or not since I don't care to worry about which fuel is being sold.  Winter blend/ summer blend may also play a part in lubricity and health of the VP.

[Threadzy]

As @Mopar1973Man has stated. Not running your fuel return into the basket helps because you’re not recycling hot fuel back to the VP44. I would see fuel temps as high as 165 while towing in the summer. Last fall I moved my return to the filler neck.  Next month we’re taking the trailer out. Outside temps will more than likely be 100 give or take. With the Quad I will be able to see any difference it made. Maybe splicing into the lift pump power source with a toggle switch or some sort of timer you could have the pump circulate fuel once the truck is shut off? I assume the overflow valve would still work and circulate the fuel if it’s above 14 psi? 

[Haggar]

W-T  I think post running circulation would make a big difference.   The stanadyne on the GM 6.5 had a similar issue..  The fuel valve solenoid gets hot.   I have a good friend that I have been bouncing this around with.  He has been watching some of the European videos where they are going in and replacing the driver chips.  (remember I am mechanical so may not be correct on the proper electrical terminology) He said that the drivers seem to be very small and fragile looking. 

 

It may be worth some time to improve cooling.

 

Hag

[Silverwolf2691]

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..

 

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.

Edited May 25, 2021 by Silverwolf2691