Engine/Transmission (1998.5 - 2002) lift pump pressure???

[DonMann]

Hi Guys. Newbie here. Been reading for a while, just joined up. Great source of info. My 01 is new to me and I see the OE lift pump has been removed and the "dealer upgraded intank pump" has been installed. I confirmed this with the dealer where I bought the truck. I hooked up our shop fuel pressure guage to the schrade valve today and noted 8psi at idle and 6psi at 3000rpm with no load. I understand the idiot light for low pressure trips at 5psi. I have a stewart/warner gauge I am going to instal pre filter. My question is this. Is the 8psi at idle and 6psi at 3000rpm correct and will it be adequate for the vp44 when hauling a moderate load (camper and small trailer). No other upgrades to this baby at this time. Thanks for your time.



Don

 

[dmhollister]

That sounds like what I am getting out of my intank lift pump. I was able to pull down to 3psi when pulling jeep to moab this year up over vail pass at 70MPH, backed down to 55 MPH and pressure back up over 5psi. Should be OK by some on this forum, But others insist on have constant 15psi at pump. It is your overall choice to follow who you want.

 

[SnoKing]

DC knows some kind of magic to get fuel to flow without any pressure behind it. "Magic, pure xxxxing magic!" SNOKING

 

[Texas Diesel]

Not magic, just physics.



(back) pressure occurs when you try and move more volume then will flow through a given orfice. Max FLOW accurs when the load (VP) and lines can handle the FREE flow from the lift pump. Pressure is not your friend.



Think of it like this, a pump producing 1 GPM (assuming an ideal and constant viscosity) flowing a fluid though a pipe capable of flowing 1GPM will move 1 GPM. Easy enough! But, install a 2 GPM pump on the same 1 GPM line and you have (back)pressure of X PSI. And the flow will be = or < 1 GPM. Pressure is a measure of mismatch.



The same holds true for radio theory, a VSWR (RF equivalent of PSI) of 1. 1:1 is the same as 0PSI as measure AFTER the pumping device. A VSWR of 2:1 indicates BACK flowing voltage (think higher PSI) from the load (antenna).



If you dont belive this, do a search for "pumps, lines and what not". The man demonstrated that max FLOW occurs at 0 PSI back pressure measured after the pump.



DC knows what they are doing, FLOW FLOW FLOW is what the VP needs, not "Tim Allen" style of manly back pressure!!!



The inlet vane pump on the VP is a positive displacement pump, meaning that the vanes and decreasing area under the vanes will determine the fuel quantity of FLOW through the pump. If I remember correctly there is a pressure relief valve to bypass VP to keep pressure down.



Have a little fun (I did this little experiment), take the return line to the tank and run it into a container. Note how small the quantity is. Then unplug the LP (dont let it stop in a fuel obstruction position!!!!, check for a negative pressure (suction) at the VP!!!) and watch the return fuel. No detectable difference :-laf But some will argue that the "extra" fuel/pressure somehow magically "cools" the VP :-laf Those that hold to this myth dont bother with, they wont listen.



If you want to lower your VP temps add fiber washers (4) under the FF bracket, that will drop the inlet fuel temp about 30F. Then go Bobs route and add a fuel cooler between the filter and the VP.



My VP runs about 130F max on a hot tow. (yea yea, heat soak, whatever... I am not installing bilge blowers, NO ONE has given any evidence that a fan cools the VP INTERNALS!!, the closest was Tim? at City Diesel but he had a temp probe installed in the potting material only)



The real test would be a gauge that could read suction at the VP. 0 PSI is cool, suction is wayyyyyyyyyyy bad!

 

[16919]

Say what you want about physics this and that or DC knowing how to fix it etc. BOSCH... ... . BOSCH the makers of the pump, say that you need a minimum if 5psi to completely fill the pump for use. I don't care what anyone else tries to say. I will go off of what the manufacturer says. I am not trying to offend anyone just stating the facts.

 

[Texas Diesel]

No offence taken!



But, can you post a link to where Bosch says that? I've read, 5, 8, & 10PSI as Bosch numbers and no one has been able to document.



If you have factual data I'd like to read it. Most often it is just hear say stuff.



No offence intended either



If Bosch indeed said "5 PSI minimum" then I would like to read it.

 

[DJW]

TD the hardest thing is to try and explain the difference between Flow and Pressure, (may never the twain will meet) many can't grasp the difference, they think they go hand in hand, whereas it's not always the case, as for some "The More the Better," whereas in many, but not all cases, too much pressure and lack of volume is the cause of the problem. On checking at a Bosh injection shop, I was told that one should not see under 8 lbs. pressure, granted pressure is much easier to verify, without having to explain and go into details, by seeing less than 8 lbs. with the factory setup, lines, hoses etc. assuming clean fuel filter, full Wattage to fuel pump fuel tank not starved for air, (and many other details too numerous to mention) As a thought, I wonder if an easy (cheap?) device could be built to enable to check the Lift Pump, meaning that the lift pump would be taken off the engine, correct Wattage applied, a gallon or so container hooked up one side and likewise the other, and pumping to the same height as the vp44, if desired a pressure gauge attached to the pump, that way one would be checking the pump and not the whole system. Perhaps Bosh could also give information regarding Flow and Pressure. Officially

 

[SnoKing]

Not magic, just physics.



(back) pressure occurs when you try and move more volume then will flow through a given orfice. Max FLOW accurs when the load (VP) and lines can handle the FREE flow from the lift pump. Pressure is not your friend.



Think of it like this, a pump producing 1 GPM (assuming an ideal and constant viscosity) flowing a fluid though a pipe capable of flowing 1GPM will move 1 GPM. Easy enough! But, install a 2 GPM pump on the same 1 GPM line and you have (back)pressure of X PSI. And the flow will be = or < 1 GPM. Pressure is a measure of mismatch.



The same holds true for radio theory, a VSWR (RF equivalent of PSI) of 1. 1:1 is the same as 0PSI as measure AFTER the pumping device. A VSWR of 2:1 indicates BACK flowing voltage (think higher PSI) from the load (antenna).



If you dont belive this, do a search for "pumps, lines and what not". The man demonstrated that max FLOW occurs at 0 PSI back pressure measured after the pump.



DC knows what they are doing, FLOW FLOW FLOW is what the VP needs, not "Tim Allen" style of manly back pressure!!!



The inlet vane pump on the VP is a positive displacement pump, meaning that the vanes and decreasing area under the vanes will determine the fuel quantity of FLOW through the pump. If I remember correctly there is a pressure relief valve to bypass VP to keep pressure down.



Have a little fun (I did this little experiment), take the return line to the tank and run it into a container. Note how small the quantity is. Then unplug the LP (dont let it stop in a fuel obstruction position!!!!, check for a negative pressure (suction) at the VP!!!) and watch the return fuel. No detectable difference :-laf But some will argue that the "extra" fuel/pressure somehow magically "cools" the VP :-laf Those that hold to this myth dont bother with, they wont listen.



If you want to lower your VP temps add fiber washers (4) under the FF bracket, that will drop the inlet fuel temp about 30F. Then go Bobs route and add a fuel cooler between the filter and the VP.



My VP runs about 130F max on a hot tow. (yea yea, heat soak, whatever... I am not installing bilge blowers, NO ONE has given any evidence that a fan cools the VP INTERNALS!!, the closest was Tim? at City Diesel but he had a temp probe installed in the potting material only)



The real test would be a gauge that could read suction at the VP. 0 PSI is cool, suction is wayyyyyyyyyyy bad!

Go read this site info:

Info: Pump Head vs Flow Rate - Overclock.net - Overclocking.net



Now get your fuel filter plugged up a bit with junk and see how the intank pump at 5- lbs does. At 12-15 lbs a filter plugged up and dropping output of the filter by 5 or 6 lbs and you still have pressure to spare. Now do the same thing with the intank pump.



SNOKING

 

[JKinney]

Hi Guys. I have a stewart/warner gauge I am going to instal pre filter.



Don

If I were to install only one guage, I would install post filter. Install the guage, new fuel filter get some base readings and run from there. You will never know when your fuel filter is plugged pre filter. I just changed out a filter on my rig that had intermitently 4 psi under load. That filter had three thousand miles on it. I now idle 17 15. 5 under load.

 

[Texas Diesel]

Pressure does not equate to flow. Some just cant grasp that.



Does anyone have a link to the "pumps lines and what not" thread from 2001? The guys $6000 flow meter tells all...



DJW, well said!



JamesThomas, I gather you dont have any links to where Bosch "said" that the VP requires 5PSI. Like I said, there are many rumors about 5,8,10 PSI being "required by Bosch" but everytime I ask where that came from there is never an answer. The VP in tractor applications doesnt even have a lift pump. And the VE pump (non computerized version of the VP) has only a priming pump.

 

[Texas Diesel]

Say what you want about physics this and that or DC knowing how to fix it etc. BOSCH... ... . BOSCH the makers of the pump, say that you need a minimum if 5psi to completely fill the pump for use. I don't care what anyone else tries to say. I will go off of what the manufacturer says. I am not trying to offend anyone just stating the facts.

I would still like to read this from Bosch.

 

[Texas Diesel]

As a matter of fact, in the book "Diesel-Engine Management" written by Bosch, on page 162, there is a cut away drawing of the VP-44. Figure 3 shows the "vane supply pump" for fuel INDUCTION (to the VP-44) and the pressure control valve loacated AFTER the vane pump.



( I have read the entire book on Bosch Diesel engine management, I suggest you might want to get a copy and read it too)



Next is the high pressure pump with distributor head.



Even with JUST THE built in vane pump, Bosch wants to limit the pressure fed to the high pressure injection pump side. Can the built in pressure regulator handle all the fuel pressure you are feeding the VP?



No mention is made in the entire book about a seperate lift pump. It would seem the LP is a Dodge item.



Nor is any mention made about requiring the VP to be pressure fed.



Sounds like the 5PSI (or 8 or 10) is just another myth. Unless you can indicate where Bosch said "8 PSI minimum" this sounds just like another rumor.

 

[Texas Diesel]

More:

Page 214,



"The low pressure stage delivers sufficient fuel for the high-pressure stage and generates the pressure for the high pressure timing device... The purpose of the vane-type supply pump (fig 1) is to draw in a sufficient quantity of fuel and to generate the required internal pressure"



If you feed in more fuel via inlet pressure you may over-ride the built in fuel pressure regulator and effect the timing control circuit. Perhaps this is why Chrysler runs the lift pump at 50% duty cycle during cranking.



If BOSCH says the low pressure vane supply pump is sufficient, I find it difficult to beleive that Bosch would say "5 PSI minimum" at the inlet to the VP44

 

[Texas Diesel]

Correction:



Pg 82 refers to a seperate "pre-supply" pump that may be added to passenger cars. There is some interesting dialogue about installation and fuel pre and after cooling and regulators. But the chapter on the VP44 makes no mention of a seperate "pre-supply" pump.



Pg 98 refers to the presupply pump providing extra fuel to absorb heat from the VP via the overflow valve. There are about 10 pages total on presupply pumps. The reason given for the presuppply pump is fuel height difference and high pressure pump cooling.

 

[SnoKing]

Pg 98 - Well Duh! What have we been saying for the last few years. SNOKING

 

[BTighe]

so would adding bigger fuel supply lines to increase flow of fuel cool the pump in the same manner as added pressure?

also, i like the idea of getting the FP reading post filter. is there a kit or something i can buy to pick up my reading there? thanks

 

[DJW]

Regarding troubles found in manufactured goods, most consumers want products built Down to a Price, and Not Up to an Ideal, a manufacture's greatest dilemma, The Engineer knows what is wanted in a product, the Comptroller and the Stylists knows what the Public will accept. Cheap, Cheap, Cheap, and not even a bona fide Chicken Ranch. It's what the public accepts, somone once said,"No company ever went broke underestimating the intelligence of the public. " In the 50s I worked at a Farm and Heavy machinery repair shop. The successful ranchers would bring in Brand New Machinery to go over every weld, reinforce this and that, alter something else, in fact everything they had trouble before, then during Harvest time they went through the whole season without bringing anything in for repair. Forewarned, Forearmed.

 

[Texas Diesel]

You neglect one thing, the VP has a positive displacement vane pump built in already. Since the vane pump is positive displacement, no extra fuel can flow through.



This is why the VP can be used in a stand alone (no presupply pump) configuration in other applications.



This is why I made this statement:

"Page 214,



"The low pressure stage delivers sufficient fuel for the high-pressure stage and generates the pressure for the high pressure timing device... The purpose of the vane-type supply pump (fig 1) is to draw in a sufficient quantity of fuel and to generate the required internal pressure"



If you feed in more fuel via inlet pressure you may over-ride the built in fuel pressure regulator and effect the timing control circuit. Perhaps this is why Chrysler runs the lift pump at 50% duty cycle during cranking.



If BOSCH says the low pressure vane supply pump is sufficient, I find it difficult to beleive that Bosch would say "5 PSI minimum" at the inlet to the VP44"



The presupply pumps are mentioned on about page 90, the VP specifically is addressed on page 208-235 as well as the VP30, VP29, VP36, VP37, & VP15. None of the VP series of injection pumps makes any reference to the "need" for a presupply pump.



In case you missed it: The low pressure stage delivers sufficient fuel for the high-pressure stage and generates the pressure for the high pressure timing device... The purpose of the vane-type supply pump (fig 1) is to draw in a sufficient quantity of fuel and to generate the required internal pressure"



I'm not sure if you are after the real truth of the matter or just fishing for things to backup your opinion.



The statement on pg 98 about extra fuel being used to cool the pump via the overflow (not overpressure) valve IMO pertains to the injection pumps that dont include a built in supply pump. The VP may be excluded because the VP has a vane pump built in that Bosch says produces "sufficient" fuel pressure and fuel quantity.



Go measure the fuel return quantity with and with out your LP. You will be surprised how close they are.



Lubricity and fuel temp are being neglected as you focus on Tim Allen LP pressure :-laf

 

[Texas Diesel]

so would adding bigger fuel supply lines to increase flow of fuel cool the pump in the same manner as added pressure?

also, i like the idea of getting the FP reading post filter. is there a kit or something i can buy to pick up my reading there? thanks

Remember back where I quoted how the VP worked and how the overflow valve bypasses the output from the built in vane pump? If you provide more fuel (via pressure) than that valve can safely bypass, you will increase internal prssure and directly advance the injection timing beyond what the control circuits want.



I have 1/2" fuel lines and a tank mounted LP. 15PSI max, I know the overflow valve can handle 15PSI (because I have a stock banjo fitting on the VP as a flow restrictor). I understand the quest for massive VP inlet pressure here and have noted the VP failures inspite of massive LP pressure :-laf



Want your VP to live a happy life? Cool the fuel, add lubricity and keep some limited degree of positive pressure at the VP, or make sure there is never a restriction caused by a stalled LP.



https://www.turbodieselregister.com...on-1998-5-2002/11672-pumps-lines-whatnot.html



Injection Pump Failures



There is a statement about low LP pressure that I will leave alone. Specifically read the paragraph about mechanical failures (lubricity related)



Bosch® VP44 Electronic Diesel Fuel Injection Pump

Neat pictures



http://www.arb.ca.gov/fuels/gasoline/meeting/2003/022003bosch.pdf

READ PAGE 16 This is why I add 2 cycle oil to improve lubricity. When my original VP failed (I bought the truck with 120,000 miles) and the dreaded 216 code came up, I drove it for another month by doubling the amount of 2 cycle oil normally added. My son laughed at the 2 cycle idea until his VP died. Then he started adding 2 cycle oil to the fuel and he drove his truck with the bad VP for several weeks until he had time to have the VP replaced. It is amazing how well even failed (216 code) Vp's respond to lubricity improvements.



https://www.turbodieselregister.com...07/120758-bosch-recomendations-lubricity.html