Disassembled A Bosch Vp44 Injection Pump

[diesel4life]

Nick, that's how it looked to me. Hmmmm....... I wonder about hogging out the relief valve for better flow? I just think a diagram as to how it flows will help people understand how IMPORTANT having over 14 PSI at all times.

Ed

Or perhaps unimportant. There is a thread over on TDR that has been running for several years, and it's about 50/50 as to the guys that run stock lp vs aftermarket. Quite a few guys running on the original VP with the stock Carter pumps.

Things that make you go hmm.

[Yankneck696]

I see it as a cooling issue. I THINK dead pedal issues in the VP44 itself are caused by a computer malfunction & removing the most heat will reduce those malfunctions. Mercruiser & the QSB Cummins both use fuel to cool their ECMs.

This is just my line of thinking.

Ed

[Mopar1973Man]

I see it as a cooling issue. I THINK dead pedal issues in the VP44 itself are caused by a computer malfunction & removing the most heat will reduce those malfunctions. Mercruiser & the QSB Cummins both use fuel to cool their ECMs.

This is just my line of thinking.

Ed

 

This is why I suggest the 14-20 PSI fuel pressure to keep the overflow valve open fully and flowing maximum amount of fuel flow for return.

 

[Mopar1973Man]

Flow paths I could figure out.

 

Supply is on the right banjo fitting and return is on the left banjo fitting.

 

Return comes from the distributor rotor.

 

Looking at the distributor and the ports.

 

Vane Pump to the distributor.

 

From the timing piston to the vane pump?

 

Valve for the timing piston.

 

Check Valve

 

Check Valve to the vane pump.

 

 

I can tell you the return flow is what is left over after the rotor is done pumping. I can tell you that the cooling of the PSG is done with cold supply fuel from the tank not return fuel.

 

Sorry about screwing up the PSG photo. I got the lid pried off and drop a few chips in the gel figuring it would just blow off with out touching the gel to get them. I found out the gel is like a thick clear grease.

[Me78569]

yep cooling is done right as soon as fuel goes into the vp

 

HOWEVER the amount of fuel that goes into the vp depends on if the overflow valve is open or not.   Realitivly stagnate fuel is going to do a poorer job of cooling than moving fluid. 

 

 

Good job on the Pictures, it is looking good.

Edited January 23, 2014 by me78569

[dripley]

How really stagnant is the fuel going to be if the pump is bringing in 70% more fuel than it needs? I seem to remember that 70% of the fuel is returned to the tank.

[Mopar1973Man]

Here you go...

http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/25-fuel-system/88-bosch-vp44-injection-pump-overflow-valve

 

Overflow Valve Operation

Fuel volume from the fuel transfer (lift) pump will always provide more fuel than the fuel injection pump requires. The overflow valve (a check valve) is used to route excess fuel through the fuel return line and back to the fuel tank. Approximately 70% of supplied fuel is returned to the fuel tank. The valve opens at approximately 97 kPa (14 psi).

 

[Me78569]

so if I am understanding what the article is saying means that if the check valve is not open then the only fuel going back to the tank is whatever comes out of the back of the head ( very little)

 

That makes sense because there are only two places fuel can flow back to the tank,. overflow whihc doesn't open unless over 14psi, and the back of the head. 

 

So if that is correct then the fule is VERY stagnate when pressure is below 14psi. 

 

The 70% going back to the tank doesn't seem like a hard number really.  I can't say I believe anyone that says that %70 of the stock 30ish GPH provided from a stock pump flows back to the tank from the back of the head.  the VP44 will be using a set amount of fuel based upon rpm and load so when we increase the GPH flowing through it that 70% number should increase.  

 

Again though if the overflow valve isn't open then what does that % drop to?  5%  ?  

 

Do we know how much fuel flows from the back of the head? 

Edited January 24, 2014 by me78569

[dripley]

Looking at the first picture in post 44 it appears the fuel comes in the VP into the bowl on the right, thru the opening into the chamber on the left. The computer rests on top of these and all the fuel, for combustion and return, that goes thru the pump cools the computer. That is why I was wondering how stagnant the fuel could get. 

[Me78569]

Anything that goes into the pump does cool the computer, but if we assume that the vp44 sends %70 of the fuel back then, when the overflow valve is closed the comptuer is only seeing ~%30 of the fuel flow it could see, plus whatever is leaking out of the back of the head ( very little).  Now if we open up the overflow then the comptuer is seeing %100 of the flow that is possible because 30% is flowing through always, then an addition %70 is flowing through the vp and out the overflow.  

 

Overflow closed the vp is only seeing 30 gph from a 100 gph pump

Overflow open the vp is seeing 100GPH

 

 

Seems to me for good cooling you want to see %100 of the fuel flow possible right?

[Mopar1973Man]

Another argument is the vane pump inside will boost the pressure as well. Bad part is no one knows how much volume that pump can put out at 400-1600 RPM which exactly half of the crank speed which is 800-3200 RPM's. Then the fact looking at the return port hole is much smaller versus the supply hole. So once again a good 14-20 PSI is fine 10-13 PSI is marginal (discounting the vane pump). Absolutely no reason for pressures above 20 PSI.

 

Now another neat thing is looking at the 3 pump plungers they are not spring loaded. They are pushed out with fuel pressure from the vane and lift pumps. I kind of want to figure out a way to open up the distributor part to show that part which does the actual pumping.

 

But I can see the P0216 code for sure. I'm going to have to say that 90% of that failure would be a lubricity issues more so that fuel pressure. Being the piston wear is lubricity issue more so being the entire piston submerged in diesel fuel.

[dripley]

I would not disagree with that at all. Fully open return valve=full fuel flow. Even at 30 GPH thats a 1/2 a GPM thru that small bowl. It just did'nt seem that stagnant to me. Of course if something require 100 GPH and only gets 30, stagnant could be a fair description.

[Killer223]

Or perhaps unimportant. There is a thread over on TDR that has been running for several years, and it's about 50/50 as to the guys that run stock lp vs aftermarket. Quite a few guys running on the original VP with the stock Carter pumps.

Things that make you go hmm.

I'm not on the other thread, but i'm one of the stock in tank lift pump @ 20+ psi, and over 62K on this pump. fingers are crossed as to how long it'll last, its had a steady diet of 2 stroke sense i've owned the truck. even last week i got some 5% bio and still added the 2 stroke. well. i saw the 5% after already adding the oil. but still can't over lubricate. 

kinda like a woman, the more lubed they are then longer they can run. 

[Mopar1973Man]

I'm also thinking more electronic failures of the PSG is cause more so from failed alternator and not heat cycle or heat from the VP44. Being a majority of people now have a good fuel system and can hold 14-20 PSI I'm going to bet its mostly AC noise blowing out small part on the PSG circuit board. I'll admit yes hot summer day and park and heat soak that pump. But if you have at least a FASS DDRP or similar you should be able to flood that first chamber with cold fuel in a few seconds. My VP44 will be going on 10 years old this spring with almost 200k miles on it. Seeing summer heat of Riggins, ID every year at 110-115*F every summer.

 

Kind like the previous post about stock carter and stock VP44 still going well into the 200k mile range. Does make you wonder. But no one has a ll the details on that either. Does the owner have a fuel pressure gauge? Using 2 Cycle oil or fuel additives? Fuel filters how good and what brand? Is the truck just a daily grocery getter or what?

 

Kind of like me bouncing back and stating I've got fully OEM stock front end parts on my 1996 Dodge with no issues of death wobble. Only changed ball joint and a track bar on my 02 and still OE parts on it. Gotta look at the type of use, type of modification that might effect longevity, driver/owner knowledge, etc.

[Texas CTD]

So when are you going to be able to repair our toasted VP44's??

[Mopar1973Man]

So when are you going to be able to repair our toasted VP44's??

 

Still way above me for that venture.

 

But.... Now with what I'm learning about the pump I think we can now work on way to improve the longevity and not even worry about failures. I still would have to say most of all the failures are listed over on my article page. Majority of the failures tend to revolve around the PSG unit on top of the VP44.

 

Even to take the timing piston out requires quite a bit of disassembly to get it out. If its like the pump I have here you most likely are not going to save the timing piston nor be able to repair it properly. At that point I can say the P0216 code is cause from a timing piston failure and its going to be wrapped up in either fuel pressure or HFRR in the case of this VP44 it was more so the HFRR was too high and the piston galled up till it seized. Even with a steel sleeve in the piston bore it galled the piston and the bore.

 

Now as for the P0251, P0252, P0253, P0254, P0215, and P1689 you can bet money the AC noise from a bad alternator most likely killed the PSG possibly a heat issue on the PSG but I've only seen one report of P0168 VP44 overheat. Being the only thing the PSG has is a tone wheel inside the pump, hydraulic valve to control timing piston and a solenoid to control fuelling. That's it the PSG is a very simple controller and limited to what it can do by the software flash to it at calibration time on the bench.

[rancherman]

is there any way to see if the  vane pump pressure  is  regulated/protected?     (excess  thrown into  main body  or   head return?)

 

 

 

whoops,   I  might of  posted that a little quick!   some  vane pumps  can be self  regulating....  or   utilized as   'on demand'  type pumps.      Pressure,  or lack of,  can   'adjust'  how aggressive  the  vanes  are  in the  pump body

Edited January 25, 2014 by rancherman

[Mopar1973Man]

The article page has been updated as well now to show the parts within the Bosch VP44 Injection Pump.

http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/25-fuel-system/437-bosch-vp44-injection-pump-exploded-view

[Mopar1973Man]

Funny... Over on CumminsForum.com they are still trying to figure out where this diaphragm is located at?

http://www3.jasperengines.com/blog/2011/12/02/jasper-remanufactures-vp44-diesel-injection-pumps/

 

 

A thicker, metal-plated diaphragm is installed to help eliminate low fuel pressure problems within the pump.

 

Perhaps the most common failure on the VP44 is the “216″ code (fuel timing error), and the runnability problems that go with it, due to supply pump issues and low fuel pressure to the injection pump. “The pump diaphragm can crack inside the pump, causing excessive wear on the housing,” says Abrams. “JASPER installs the later-style diaphragm, which is metal-plated and is thicker than the original, to help eliminate these types of failures.” Abrams added, “On each VP44 replacement, JASPER recommends that the fuel supply pump is also replaced in the vehicle to help eliminate that failure.”

 

Funny here is a Bosch reseal kit...

 

No diaphragm in the kit? Hmmm....

[hex0rz]

I wouldn't trust JASPER with a 10 foot pole!

 

Never had first-hand experience with them, but by-golly, I've never seen a soul speak highly of them.