Will the member please come forward that sent me the VP44...

mike,  is that  'diaphragm'     that the  guy is holding in the picture....    is  NOT  in the pump>  you haven't seen it  anywhere  in your  tear-down?

 

It  amazes  me  that    15 plus years   AFTER  it's  debut,    someone  finally   lifted the curtain/peeked up the  skirt...

 

Yea... They thought it was the end cap off the distributor part.

 

Here is what's in the distributor head.

 

Here is the part they think is the diaphragm.

 

 

That thing is a steel plate with a plastic back with a rim to hold the o-ring in. The first thought that comes to mind with diaphragm is a rubber barrier that flexes. This is a steel plate very very solid steel and its not going to CRACK.

 

It  amazes  me  that    15 plus years   AFTER  it's  debut,    someone  finally   lifted the curtain/peeked up the  skirt...

 

 

I would of done it sooner if I didn't have to pay 300-400 for a core pump! Once again give Diesel4Life a big round of applause for sending me that pump to tear apart.

We should tally up all the slimeballs who have been trying to pull a hoodwink on people...

These rumors run wild.  There is a timing advance slot in the 215 ppump plungers that everyone has stated completely wrong rumors about.  There are vastly different timing charts for setting the timing on the ppump which means you have no clue which one is right (which is why I spill port time mine).  There are also the very same fuel pressure limits blowing out some seal which I have never found.  BS sells. 

What does Bosch call that part you found? Is there a parts list that goes with the exploded view? Maybe this "diaphragm" does not do what I or we think a diaphragm normally does. I dont know, just paying devils advocate here.

What does Bosch call that part you found? Is there a parts list that goes with the exploded view? Maybe this "diaphragm" does not do what I or we think a diaphragm normally does. I dont know, just paying devils advocate here.

 

According to Bosch #50 is sealed unit. This why there is no listing of the rotor inside or anything else.

 

 

 

Now we have... This is a thick steel plate with a plastic backing.

 

So explain this pic... Gotta be rubber or something brittle?

I cant explain the C shaped piece. Maybe it is the old design they had so much trouble with. The shape does not make any sense for a "diaphragm" or seal of any kind. Definitely over my head.

can you tell if  that   'diaphragm'  is  there  for

1.   sealing.   Does  it have the capacity to   seal itself  both inner or outer  diameter?    Does it look  like it  could   move  along the  shaft.. much like   a   piston  in  a  clutch pack?

2.   as  a   bushing.     Plastic on one side for  antifriction  surface.    Distributor   is    'located'  depth wise  by  this  'spacer'?

Edited January 31, 201411 yr by rancherman

My  edit  feature  is  haywire...  so here goes

 

the  'pocket'   behind the assembled   diaphragm...  does  anything  change  if  it moves  in or out?    possibly there  just  as  a   'cushion/reservoir'..      

 

the  3  'rollers'   radially  placed  on the  diaphragm...    what  do they   ride on  when  assembled?

I would guess they ride on the "diaphram"

 

The pocket behind looks to have holes on the outside edge to left pressure out I would assume thus pushing fuel into the chamber and back to the tank?  ( mike correct my her because I am flying pretty blind.)

 

 

But the fact is that jasper and bluechip both say code 216 is due to a cranked "diaphram" causing time to not advance, well the Timing advance piston isn't link to the "diaphram" as explained by Mike.

Edited January 31, 201411 yr by me78569

I'm wondering if we could get a rebuilder to chime in...

 

...yea, I know, when pigs fly!

Michael

 

I've been looking a little more at the operation of the VP-44.  With the help of your excellent breakdown pictures, as well as other info I've accumulated, here are some of my thoughts:

 

The supply pressure (downstream of the vane pump) fills most of the pump body, but the actual flow path to the injection piston enters through ports in the distributor head (DH).  This flow path is cut off by the Pump Control Unit (PCU) at the proper times and the cam ring actuates the injector plunger which sends the high pressure injection fuel to the distributor and out to the desired injector.  The amount of fuel that is used is controlled by the PCU.  The timing is controlled by the timing valve and cam ring.  When that happens (because all of the fuel in the injection piston is not used), some is spilled back into the main body.  This creates a pressure surge that would cause  disturbance to anything that is supplied by the vane pump, including the timing piston.  To lessen this pressure surge, a diaphragm is used between the head unit and the intermediate chamber.

 

This diaphragm is described thus:  "A diaphragm is installed in the distributor head at the inlet supply bores of the distributor shaft.  The diaphragm evens the pressure peaks which occur during spill (end of pump deliver)".  My guess is that it acts like kind of a buffer which partially adsorbs the pressure spike.  I can see where a ruptured diaphragm could allow these pressure spikes to have a greater effect on the pressure in the chamber and possibly screw up the timing piston operation.  These pressure spikes could possibly be felt as far back as the vane pump input which might explain why some fuel pump pressure gauges get the hell banged out of them when the pump is in operation.

 

Yet to be determined is what pressure the vane pump puts out.  Info I have says the output pressure varies with the rotational speed of the injection pump, which makes sense.  As you have pointed out, there is relief valve that opens to bypass the vane pump output back to the inlet if pressure gets too high.

 

Also, everything I can find on the overflow valve indicates it comes right  off of the ports in distributor head but probably has flow through it whenever the vane pump is operating.

 

Just my thoughts; I've been wrong before.

 

Problems still remains there isn't a diaphragm in the pump Iive got here on my shop bench which happens to be a 027 Rev VP44 pump. I've still got that piece of the distributor head laying on my desk and its a solid steel plate with a plastic back to hold the o-ring. I've been hunting around the internet and talking to people and still to this day no one can find a Bosch part number or a Bosch seal kit that contains this "diaphragm".

 

There is no physical way for me to break this disc. Like I said its a solid steel ring. It not rubber like shown below.

 

 

Once again this is a solid steel ring.

 

 

I agree that a solid steel thing-a-ma-jig would be very difficult to rupture.  It is my understanding that the diaphragm problem has been addressed by Bosch. It has been made stronger during rebuilds, but I believe it still performs its original functional.  Maybe the one you have has the upgrade. I think that upgrade came out on rebuilt units quite a while ago.

 

Never-the-less, both the training manual and the service manual that I have  talk very plainly about the 'diaphragm' and its purpose so I'm pretty much convinced it does exist.  The exploded illustration in the service manual lists it as piece 50-13.

 

Both of these manuals that I have are put out by Bosch. The training manual is a 1996 version, but the service manual has a date of 2000.  To do its job the diaphragm only has to flex .5mm (about .02 in).

 

Again~~just my opinion!

 

Humbly

jim

 

Hmmm... The information I've got is from 2009.

The more I learn about the VP44, the more I learn how little I know. 

 

Here are some more of my opinions:

 

The only places the vane pump supplies pressure are the distributor head accumulator bowl and the timing piston.  Everything else is supplied by the feed (lift) pump pressure (including the cavities within the VP). 

 

The accumulator bowl gets its pressure from the vane pump through the ports in the housing and supplies fuel to the high pressure injection piston input passages.  This piston’s input and output are controlled by Power Control Unit (PCU) which, in turn is controlled by the Engine Control Module (ECM).

 

The disputed diaphragm separates the accumulator bowl (which is at vane pump pressure) from the body of the VP (which is at feed pump pressure).     When the High Pressure Cam is pushing fuel into the injection piston cavity, the length of time it is allowed to pass fluid into it is determined by the PCU.  When the PCU says that’s enough, the valve closes and fuel from the injection piston stops.  However, the cam is still trying to deliver fuel.  This is diverted back to the accumulator bowl where it causes pressure spikes.  The purposed of the diaphragm is to flex ever-so-slightly (less than .5 mm (about 0.02 inches)) and absorb these pressure spikes.  Fuel is now added to the chamber by the vane pump to make up for what has been used and the process starts all over for the next cylinder.

 

Since this diaphragm exists between the accumulator chamber (vane pump pressure) and the body cavity, which is at feed pump pressure, I can see where a ruptured diaphragm could cause problems.  If it was damaged, the pressure spike could be felt back at the VP inlet (even far enough back to break your fuel pump pressure gauge).

 

Also, the timing piston, in addition to using vane pump pressure on its high side, uses feed pump pressure on its low side.  If this low side pressure becomes unstable, I can see where it could cause problems with the timing.

 

Since the timing piston is controlled both by vane pump pressure and by feed pump pressure, I believe that too much feed pump pressure also could restrict its operation and thus alter the timing and cause hard starting.  This might explain why too much feed pressure causes hard starts.

 

I can also see why Dodge recommends a minimum of 10 psi feed pump pressure.  Any less than that could cause abnormal flexing of the diaphragm.  I don’t think that’s a problem anymore, because you (Michael) have found that the diaphragm is pretty tough stuff.  I think recent rebuilds of the VP have pretty much eliminated the problem of a damaged diaphragm.

 

It’s also worthy of noting that the Dodge Ram is not the first time the VP44 has been used.  It’s been around for a lot longer than we have used it, and in many cases there is no feed pump being used, relying only on the vane pump to make it work.  God only knows how many million Rams are running around right now with zero feed pressure.

 

In conclusion, I believe the risk of a damaged diaphragm due to low pressure is, indeed, a myth (at least on recently installed pumps (and I have no idea what the definition of ‘recent’ is).   I also believe the diaphragm does exist and has a necessary function.

 

Still-we do need adequate fuel pressure to cool and lubricate the VP.  Based on this, I believe you are right in saying that 10-15 PSI is okay, 14-20 is probably better and there is no reason to go above 20PSI.  I know a lot of you folks run higher pressures, but I think is does effect the timing.  If it feels good, do it; it is ~~after all~~your truck.

 

Once again, just my opinions!

 

Humbly,
jim

So that chuck of steel that Mike pulled out is supposed to flex? Where did the rumors start about having to much lift pump pressure will rupture the diaphragm? Just a little confused here because it sounds like we have to ideas here. One, there is no diaphragm, and the other is there is a diaphragm....

Too much or too little FP causes it to rupture.... They are as decisive as Airdog...

 

Ed

I believe the only part that can be damaged by too much fuel pressure is the shaft seal. Push it out and your dumping fuel right down the front of the gear case.

Jeeper Jimy, which other vehicles have had the VP44? I was only aware of Dodge trucks and the UPS vans. The VP was introduced to meet the new emissions requirements and as I understood Bosch had little time to do a whole lot of R&D as Dodge was under the gun.

Actually, it & the 37 series (Virtually the same without computer) are very common in europe.

Ed

I apologize, Michael; this is going to look like another book, but~~~

 

First off:  I don't believe that I have read from any credible source that high feed pressure could rupture the diaphragm--just low feed pressure.  I think it's pretty well established that high feed pressure can cause hard starting of a warm engine.  I think this is caused by abnormal operation of the timing circuit causing it to not be in its retarded position during startup.  I guess the front seal is another possible problem area with high feed pressure, but I've never heard of one being damaged.

 

Do I believe the diaphragm that Mike is holding can Flex?

In a word~~yes!

 

Bear with me.  As the cam ring and followers squeeze fuel in the injection pump it pushes a volume of injection pressure fuel towards the port of the selected cylinder.  When the Pump Control Unit (PCU) decides that the delivery fuel is what it wanted, the valve between the feed chamber (bowl) to the injection opens.

 

The followers on the cam ring, however, have not reached the top so it is still pumping fuel.  When the valve opens back to the fuel chamber,a high-pressure spike is felt back in the chamber.  The pressure of this spike is at injection pressure value, but it is very small (probably a drop), but it has to be dealt with because when the cam follower starts to cause the injection pump to take on fuel again, it wants to be back at it's normal pressure.

 

Since the spill is being pumped back into a solid system and fuel cannot be compressed, there are a limited number of placed that can take up this extra volume.  One is back to the vane pump.  It, however, is a positive-displacement pump driven by the big Cummins engine so nothing is going to happen there--at least not in the time available.  Something has to give to dissipate this high-pressure spike.  In my humble opinion (as well as the VP44 Service Manual and the interactive training CD that I have), the diaphragm does flex.

 

Bear in mind, it only has to flex enough to compensate for the drop of high-pressure fuel that is been absorbed into a larger volume of fuel. Figuring the area of the diaphragm, the volume of the chamber, and the volume of the fuel drop, you probably could calculate how much the diaphragm has to flex to absorb this spike, but it's only a small fraction of a millimeter.  I think that calculation is beyond my capabilities (maybe I'll look into it later).  Realize that the pressure in the bowl needs to be ready for the next injection in a matter of milliseconds. This operation can occur upwards of 50 times a second).

 

Looks like a book doesn't it?  As far as the rupture of the diaphragm, I'm not sure why that happens (if it does), except that, apparently--in the early days of its use in the Cummins, the diaphragm would flex beyond it normal operating range with too little feed pump pressure.  Since the VP44 has been in use several years before that in other vehicles (Europe and possibly some tractors), any rupture must be peculiar to the 5.9 Cummins.  I think that rupture problem has been taken care of with later rebuilds of the VP, and, from Mike says, the diaphragm he has is much stronger.

 

I think the Bosch engineers must have been smoking some pretty good stuff when they engineered the VP44, but it is, after all, just a machine controlled by a computer.  There is nothing magical about it.  It's complicated but if operated with in it's design parameters, will be happy for a long time.

 

I believe one of the things that should be seriously considered in keeping it happy is keeping it lubricated and, to me, that means the use of two-cycle oil during every fillup (as recommended by Mike).  This design does date back to the days when diesel fuel had better lubricating qualities.

 

Once again, these are only my opinions, based on what I think I have learned over the last ten years.

And now~~back under my desk to Dodge the incoming flak.

Humbly,

jimmy