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

1. Yes the port is completely open.

 

2. Yes there was 15+ PSI at the time of the video.

 

3. Fuel pressure is mechanical gauge (no sensor) so that is actual input pressure to the pump.

 

The problem is you got to start the flow of fuel from the front of the pump and work your way all the way back to the rear of the pump. So now the fuel has to pass through the vane pump, then all the galleys to the rotor and then when the rotor is done then the excess fuel is sent towards the overflow valve.

 

 Thanks for the information much appreciated. #3 I should have used the term pressure gauge port instead of sensor. Some put the port before a filter as a means to know when to change the filter. Wanted to make sure the psi I saw on your gauge was the actual restriction of the VP with the volume of fuel you send it not something else like a filter. You saved me some time in trial and will now regulate pressure before the VP.

 

Cheers and enjoy your day,

 

Josh

dinosaur digging....

 

mike can you please attempt to disassemble the rotor, 

http://forum.mopar1973man.com/uploads/monthly_01_2014/post-1-0-60023200-1390428263.jpg,

and see if this large black piece is what industrial is calling the diaphram here: 

Edited December 16, 201410 yr by Off-Road

Here you go. This is a harden steel plate with a plastic cover.

 

 

that is what they call te dang diaphram.......  hmmmmm

I still shake my head. Harden steel disc held in by 1 snap ring. Then sealed with 2 o-rings one outer and one inner. Still in all the metal should protect the plastic from flexing. The metal will not flex at all I've tried.

But it will crack as seen in the above photo.  Just as the one I was shown last year at the Logging Conference in Eugene, OR.

What's the cause of the crack is my question?

Or better yet.....  Is the "crack" even a problem or is it just merely the outer plastic.  Or.....does the plastic form some kinda diaphragm seal which whereby the "crack" is allowing fuel to bypass under pressure, thus the reason why when the diaphragm cracks the timing piston is soon to follow because of it beating itself up from improper fuel timing?

Outer plastic? Majority of it a steel disc. You can see my damage from prying it out.

No, what I meant by "outer plastic" was that its a steel disc covered in plastic.  To the best of my understanding its always been plastic but the upgraded version became plastic over steel.  So that said, is the "plastic" serving as some sort of sealer?  Something about the diaphragm must be sealing because when the diaphragm fails, proper fuel timing is no longer achieved at the timing piston.

 

That's what I don't understand that disc is on the back of the rotor assembly. It has no connection with timing piston. Maybe hydraulic it might be connect dumping the pressure back in the body of the pump. I'd have to pull my pump off the shelf and pull it apart again. But the steel plate is held in by 1 snap ring and has 2 o-ring seals. The plastic can't flex with steel backing it. Like photo above I wonder about the crack like it was force or pried again from the center hub. Improper assembly? Because if you got a steel disc backing the plastic there is no way to flex the plastic. But being the crack is larger at the center hole going to the outer diameter this seem to me from prying out.

Mike can you check to see if it is out of round.... weather the diameter or radius is smaller at the crack?

I think I found the answer on this. While taking my morning shower I was thinking about that plastic backing. We all assume there is pressure there because most of us use a fuel pressure gauge. Let's assume the owner doesn't have a fuel pressure gauge and a bad fuel filter. Now the only time that plastic will flex is under a VACUUM. The plastic is not glued to the steel. So if there is a vacuum present it would pull the hub inwards and crush against the inner o-ring till it deformed and cracked.

 

Sound about right?

Another thought on this just past...

 

Now take notice the 3 ports are screens assume the screen are plugged up with debris. Then place a vacuum on the chamber. Now could you see the plastic flexing downward into the chamber till it broke or cracked on the center hub.

Hmmm…..viable.  The way it was explained to me some years ago was that the VP has three levels of pressure within itself.  High, middle, and low.  I know “middle” isn’t the correct terminology but let’s not split the hairs just yet.  So the diaphragm is situated on the low pressure side of the VP but yet because of the rotor design, the mid pressure pulses are allowed to travel back through the low pressure side.  The only thing to stop or offset those mid level fluid pulses from traveling back through the low pressure side is the pressure from the fuel pump.  And when the fuel pump pressure is too low then the mid pressure pulses are the stronger of the two and the constant wave of mid to low, mid to low, pressure signals felt by the diaphragm are what causes it to “flex” and eventually fail.  Apparently it seems were not sure what the actual failure is or if the failure is what we think it is as this diaphragm seems pretty stout.  But nonetheless…..

Sometimes I feel like the VP holds mysterious secrets like the pyramids of Egypt.  You’d think after 16 years SOMEONE would have an accurate understanding about the mystical VP diaphragm.

You'd figure after 16 years someone would of fixed these mysteries. But why invest in a obsolete technology since common rail came out.

 

As for pressures the vane pump goes directly to the rotor in those ports IIRC. As for the body of the pump its at fuel pressure level. So that would be you middle pressure from the vane to the rotor head.

You'd figure after 16 years someone would of fixed these mysteries. But why invest in a obsolete technology since common rail came out.

 

Strangely though, Cummins is not the only engine to use the VP44.  Lots of people work on the VP but the true understanding of what’s going on inside it seems to be some highly guarded secret no one will divulge.

Trust me... If I find any secrets I will gladly post all of right here.

You'd figure after 16 years someone would of fixed these mysteries. But why invest in a obsolete technology since common rail came out.

 

As for pressures the vane pump goes directly to the rotor in those ports IIRC. As for the body of the pump its at fuel pressure level. So that would be you middle pressure from the vane to the rotor head.

LOL,   yah,  why  'fix' a   'cash cow'??   

LOL,   yah,  why  'fix' a   'cash cow'??   

 

Funny part after pulling apart a VP44 the mechanical part is really easy to rebuild its just the calibration that is the hang up.