Engine/Transmission (1998.5 - 2002) Confussed on "how the low pressure side of the VP44" works.

[BradyWilliams]

The transfer pressure fuel goes in the inlet fitting then under the PSG for cooling then in the low side part of the pump housing. The fuel at 13. 5psi is picked up by the transfer pump (vane type) and is then sent to the pressure regulator. The pressure reg. vents excessive pressure back to the low side pressure pump housing. The high fuel pressure now travels through a drilling to the advance area and the head & rotor and there is where it enters the high side of the diaphram. That is how you get your high side and low side pressure.

 

[Texas Diesel]

Brett since you rebuild these things I have a question for you. Do you see any evidence of lubrication related problems i. e. , scoring, galling or any other type low lubricity failures?



TIA

 

[rweis]

Ahhh, ok



The PSG is(are) the electronics in the electronics bay correct? So there are fuel passages under or around the PSG bay to help cool the PSG.



Not knowing how the PSG is mounted, would cooling the surface of the PSG cover also help in protecting the PSG? ie I have a 235 cfm outside air blower blowing across the top of the VP44 by the PSG bay in an attempt to help keep the PSG cool during engine run and AFTER engine shutdown for 128 minutes. I also have a remote thermometer pickup mounted to the outside top of the PSG cover to monitor the PSG cover temperature in an attempt to understand what the temperature pattern the PSG is seeing. I can keep the PSG cover to no higher temperature than outside air temperature + about 20* (OAT = 90*, max PSG cover = 110*)



... fuel at 13. 5 psi ...



Does this mean 13. 5 psi is the ideal input pressure?



What if some guys are running 20 psi what effect does that have?



What if some guys are running 10 psi what effect does that have?



I see the vane pump pressure regulator and the return of the vane pump pressure regulator to the input side of the vane pump. At that point in the fuel supply system how does the very low pressure of the OEM lp (13. 5 psi) deal with the much higher return from the vane pump? Maybe because the amount of the return is very minor compared to the total vane pump intake?



I see the high side diaphram over where the vane pump pressure enters the high side. The book implies the high side diaphram is there to balance out some of the pulsating pressures from the vane pump as well as to provide a resevoir of vane pump fuel pressure. Am I even getting this close to correct understanding?



This VP44 is a really fascinating mechanism. The book helped a lot, but having some TDR members that know the REAL processes surely help a whole lot too. NOTHING like FIRST hand knowledge!



Bob Weis

 

[MKinner]

Here are a few pics that might give you a good visual. . http://www.realdiesel.com/vp44pump.html #ad

 

[rweis]

Well, I think we have a contest, "Name that part"



Upper left is #1 upper right is #4



1,2,3,4

5,6,7,8

9,10,11,12

13,14,15,16

17,18,19,20



I'll go first:



5 = cam ring for high pressure radial pistons, 6 lobes because of 6 cylinders

6 = timing device piston. cam ring 5 lug goes into slot, piston is 90* to cam ring to rotate cam ring for timing

7 = control plunger for hydraulic assisted timing device



Bob Weis

 

[MMcfall]

Here is a copy of an email request for information I received from Cummins a few days ago. Also of note - I recently had the LP and VP changed just under the 100K warranty period. The LP is the new "in-tank" one and it is a "demand" based system. The higher the demand the more it flows. It is supposed to be able to maintain 5-8 psi to a stock configured engine, well in line with the specifications from Cummins detailed below. I have a Westech FP gage connected to the Schrader valve on the VP in accordance with where Cummins says you should be monitoring FP from and my stock configured truck stays between 6-8 all the time and only drops to 5 psi when under full WOT from a standing start to 80 mph. Waiting for a similar email response directly from Bosch. If/When in it comes in I'll post it.



Wed, 04 Jan 2006 12:47:24 -0500 (EST)

From: -- email address removed --

Subject: Re: RQST00000402246





Summary: 65216 VP-44 Fuel Supply Pressure Requirement



Solution:



Thanks for your Email message.



You may need to add an additive if your fuel is in question. Lubricity and

water problems are the two big factors. For more information, contact Fleet-tech

Customer Assistance at 1-800-22FILTER(1-800-223-4583) fax 1-800-999-8664 or visit

us at www.fleetguard.com



When the transfer/lift pump fails fuel flow may or may not stop flowing to the

VP44 pump. It all has to do with the position the pump fails in. If you had a

gauge that could read positive or negative pressures on the outlet side of your

fuel filter you could see when there was a problem. At that point you could

stop and fix the problem with your truck. At that point the problem may be a

filter, plugged inlet line, transfer/lift pump or something simple.



Information about pressure:



Concerning lift pump pressures for ISB 24 valve engine, in the Ram application,

the following information is from the Cummins ISB Troubleshooting and Repair

manual, Bulletin number 3666193. This information applies to engines having the

Bosch VP-44 injection pump (not the high-pressure common rail found on 2003 or

later models).



The lift pump pressure is only one parameter pertaining to fuel system

operation/diagnostics, and as long as you have positive pressure to the VP-44 at

adequate flow, your engine should run fine. "Adequate" means normal performance,

starting and smoke levels. Any issues with the engine running outside of the

below listed pressures being in their respective proper ranges should be addressed.

The numbers in the manual are:



Idle speed:

700-1000 rpm

Maximum fuel inlet restriction to lift pump:

6 in Hg

Maximum Fuel Pressure at Fuel Filter Outlet (engine cranking): 4 - 8 psi

Minimum Fuel Pressure at Fuel Filter Inlet (engine running): 8 - 17

psi

Fuel Drain Line Maximum Restriction:

10 psi

Fuel Inlet Maximum Temperature:

165 deg. F

Engine Minimum Cranking Speed:

150 rpm



Excessive smoke can be a symptom of improper injection timing, which MAY be

caused by insufficient fuel to the VP-44. Variable pressure within the pump

rotates the cam ring that affects/effects injection timing changes; insufficient

fuel delivery to the pump will affect the pumps ability to establish the correct

timing per operational condition. Normally this is a blue-ish white smoke.

Black smoke is indicative of over-fueling (relative to the amount of air).



The fuel flow test (005-011) states to run the engine at high-idle (running on

governor with no load) speed; the outlet side of the filter should read 10 psi

minimum. To be thorough, one needs to check at high-idle as well as idle and

measure at the correct places. Under high-idle conditions the pressure drop

across the filter is to be 5 psi maximum.



The manual further states, not to operate the fuel system with suction

restriction of more than 3 psi but Bosch prefers that there is no negative pressure on

the VP-44. We are not aware of any durability validation tests at "outside of

acceptable operation" parameters or that negative pressure might cause VP-44

failures due to the lack of sufficient fuel for pump lubrication. Unlike the

P7100, the VP-44 is lubricated by the fuel which circulates through it. Bosch may

be able to advise the effects of low lift pump pressure on the VP-44 injection

pump.



The output of the fuel lift pump is checked via test (005-045-012) by measuring

the output pressure, using a pressure gauge at the fuel filter head tap. For

long injection pump life, the Bosch VP-44 pump requires clean No. 2 diesel fuel,

with no water or foreign debris. Owners should be very careful during fuel

filter maintenance or replacing the lift pump, to ensure that no debris gets into

the injection pump side of the filter.



Always use the lift pump to fill the filter. This can be done by bumping the

starter with the key switch but not starting the engine. The lift pump will run

for 25 seconds. Turn key off and repeat two more times then filter should be

full.



We thank you for your interest in Cummins products. Please let us know if you

need assistance in locating the nearest Cummins-authorized Dealer or Distributor

Service Provider. For assistance in locating a Service Provider, feel free to

use Cummins North America Dealer Locator, which can be found on Cummins website:



http://wsl.cummins.com/ServiceLocator/jsp/controller.jsp?action=servicelocator



Please let us know if you have other questions and if away from your computer

or have a time-critical request that needs more urgent attention, feel free to

call us toll-free (from North America) at 1-800-DIESELS (343-7357).



Email direct: -- email address removed --



Regards,

--

Powermaster

Customer Assistance Center

Cummins, Inc.

Columbus, Indiana, USA





Free QuickServe Online for Consumers http://quickserve.cummins.com

 

[MKinner]

Too bad they don't get a little more in detail about each part, #ad
I too am concerned about my fuel pressures now that I have my gauges installed. 11-12 psi at idle, 6 wot. Now for my next quest... 15-17 psi at idle AND wot. Wouldn't that be the perfect setup? Especially if it didn't matter how much HP you are running? I think so. If the setup I am going to install on my truck works, it will be very, very sweet.

 

[BBliss]

the answer in my opinion is to have adequate fuel pressure so that you can be assurred the their is enough flow to the injection pump under full throttle and full load. that is why a gauge or at the least a low pressure light is neccessary to determine if you have enough flow at wot and full load. it is a simple matter of needing at least 5-7 psi under these conditions. the question of pressure verses flow is not applicable. if you have enough pressure at idle so that you have enough flow to end up with postive pressure at wot and full load then you have a good set up. this is done in drag racing all the time with electric fuel pumps. if you need x number of gallons per hour flow at a certain pressure to ensure that you get enough fuel then that is what is takes. 30 psi is not neccessarily better than 15 psi as long as you have 5-7 at max load conditions. the answer seems to be around 17 psi at idle with lines and a pump with enough volume to support 5-7 psi at max load. due the math more hp requires more fuel. oh and guess what even with sufficient fuel the pumps still wear out and fail, it is just that they fail sooner when they are starved.

 

[rweis]

MKinner - RASP. The more rpm (the more fuel needed) the more fuel pumped. Mine idles at 14# and goes to 17# at 2400rpm, the bypass is set to 17# and bypasses a BUNCH of fuel. IF the engine could use it, it is there.



BrettWilliams - Your information that there are fuel passages around the PSG leans toward the idea of fuel coolers PRE VP44 to cool the PSG. That helps clarify if the fuel coolers should be pre or post VP44.



Can anyone else name (describe) some of the parts? What is it? looking from which end? and what does it do?



Bob Weis

 

[MKinner]

MKinner - RASP. The more rpm (the more fuel needed) the more fuel pumped. Mine idles at 14# and goes to 17# at 2400rpm, the bypass is set to 17# and bypasses a BUNCH of fuel. IF the engine could use it, it is there.

BrettWilliams - Your information that there are fuel passages around the PSG leans toward the idea of fuel coolers PRE VP44 to cool the PSG. That helps clarify if the fuel coolers should be pre or post VP44.

Can anyone else name (describe) some of the parts? What is it? looking from which end? and what does it do?

Bob Weis

Bob, I like your thinking! So when do you want to get together and burn a few burgers? I have a slight variation of that in mind... What kind of beer do you drink? #ad
Damn the lift pump... .

 

[rweis]

School is just getting started (I'm the network admin). I would say toward the end of Jan. Let's meet at your place, I'll bring the torch and the fittings I have left over. To build the thing the key is to have the parts ready to go. I built mine in the garage one night between 0100 - 0400.



Measure 2 cut 1. I used pipe "M" thick copper, "L" is thinner. Then there is the soft copper.



Email me your ideas on variation, probably better than mine.



Budweiser Oo. AFTER assembly



Bob Weis

 

[MKinner]

Sent you a PM.