Fuel pressure 5psi. 0 at WOT

[ColoradoColt]

Like title says, I have about 4-5 psi at idle and 0 at WOT. I used a gauge that I connected at the VP44. Does this mean new lift pump? Injection pump? 

[Mopar1973Man]

Lift pump is dead time to replace. AirDog, Fass, mechanical belt driven, etc

 

[dripley]

If it is connected right at the VP with no snubber and or a needle valve to protect either it could the gauge. I beat my first mechanical gauge to death that way.

[ColoradoColt]

This is what I used to check right at VP. Connected it just as it looks in picture. I guess that explains my surging and what seems like dead pedal even after timbo apps

[dripley]

If you are just hooking a test up forma short test then it is most likely the lift pump as @Mopar1973Man is saying. The gauge I blew was the one mounted in the cab. That pressure reading has nothing to do with the VP. Unless you feed it that way until it dies.

[Mopar1973Man]

Here is what I'm using is a Vulcan Performance fuel pressure tester. 0 to 30 PSI gauge. This is much more accurate than a 0 to 100 PSI gauge. This is 1/2 pound tick marks in the red.

 

 

I even got all the fittings for all types of fuel systems. 



[ColoradoColt]

Okay so am I okay to drive home like this you think? I’m not sure how long it’s been this bad. Just today my truck seemed to lose all power randomly for two or three seconds while I was accelerating up a steep hill. I have about a 20 mile drive home

Does anyone have a preferred or recommended  Electric lift pump? 

[Mopar1973Man]

You can drive it home but longer you drive it the way it is the more damage is being done to the VP44. The VP44 injection pump needs to have return fuel flow at 14 PSI to 20 PSI so there is cooling fuel present and excess fuel to lube the pump. Being that your below 14 PSI the return valve is CLOSED there is no cooling and no extra lubing for the pump. 

 

 

 

[Tractorman]

2 hours ago, Mopar1973Man said:

You can drive it home but longer you drive it the way it is the more damage is being done to the VP44. The VP44 injection pump needs to have return fuel flow at 14 PSI to 20 PSI so there is cooling fuel present and excess fuel to lube the pump. Being that your below 14 PSI the return valve is CLOSED there is no cooling and no extra lubing for the pump. 

 

The 14 psi overflow valve inside the VP44 provides the path for fuel return flow for cooling the VP44.  There is a fixed displacement internal gear pump ( a vane pump) with a relief setting of over 100 psi that by design provides more flow than can be consumed by the injectors and operating parts inside the VP44 with plenty of fuel flow left over to operate the 14 psi overflow valve and return fuel to the tank under all operating conditions.  

 

The lift pump flows directly to the inlet of the fixed displacement internal vane pump.  No lift pump can make the internal vane pump deliver more fuel.  A high volume lift pump that flows more fuel than the internal vane pump can flow just raises the VP44 inlet pressure, but DOES NOT flow more fuel through the internal vane pump.  It can't because the internal vane pump is fixed displacement.

 

The concept of using a lift pump is to provide a positive pressure to the VP44 inlet.  If an engine is at wide open throttle and the inlet pressure of the VP44 is only 3 psi, all is well.  3 psi means that the inlet of the VP44 is charged so the internal gear pump will take care of the rest.

 

I am posting this information because I truly believe that there were so many problems with VP44 trucks when they first came out that it generated a paranoia that can't seemed to be dropped.  The paranoia was centered around lift pump pressure early on.  However, Bosch fixed a lot of those VP44 problems without fanfare and a quality rebuilt VP44 is now pretty reliable - regardless of lift pump pressure.

 

My replacement remanufactured VP44 (timing piston failure on the original) and lift pump conversion to tank was performed under warranty at 87,000 miles in 2005.  The original lift pump never missed a beat.  The converted in-tank lift pump operated at 6 psi at idle and 3 psi at wide open throttle.  I drove it that way for over 150,000 miles with a Smarty tuner added.  I replaced the in-tank lift pump with a frame mounted used FASS pump (a low volume one) at 250,000 miles on the truck.  I did this only because I wanted an easy roadside repair in case the lift pump failed.  The FASS lift pump operates at 12 psi at idle and 5 psi wide open throttle.  That lift pump has been operating for over 4 years and 90,000 miles.  I now have over 250,000 miles logged on the rebuilt VP44.  I expect that I can have a VP44 pump failure at any time now, but I will not complain about the service life and I will not blame it on the lift pump.

 

 

- John

 

 

 

Edited June 22, 2020 by Tractorman
forgot something, as usual

[Royal Squire]

1 hour ago, Tractorman said:

 

The 14 psi overflow valve inside the VP44 provides the path for fuel return flow for cooling the VP44.  There is a fixed displacement internal gear pump ( a vane pump) with a relief setting of over 100 psi that by design provides more flow than can be consumed by the injectors and operating parts inside the VP44 with plenty of fuel flow left over to operate the 14 psi overflow valve and return fuel to the tank under all operating conditions.  

 

The lift pump flows directly to the inlet of the fixed displacement internal vane pump.  No lift pump can make the internal vane pump deliver more fuel.  A high volume lift pump that flows more fuel than the internal vane pump can flow just raises the VP44 inlet pressure, but DOES NOT flow more fuel through the internal vane pump.  It can't because the internal vane pump is fixed displacement.

 

The concept of using a lift pump is to provide a positive pressure to the VP44 inlet.  If an engine is at wide open throttle and the inlet pressure of the VP44 is only 3 psi, all is well.  3 psi means that the inlet of the VP44 is charged so the internal gear pump will take care of the rest.

 

I am posting this information because I truly believe that there were so many problems with VP44 trucks when they first came out that it generated a paranoia that can't seemed to be dropped.  The paranoia was centered around lift pump pressure early on.  However, Bosch fixed a lot of those VP44 problems without fanfare and a quality rebuilt VP44 is now pretty reliable - regardless of lift pump pressure.

 

My replacement remanufactured VP44 (timing piston failure on the original) and lift pump conversion to tank was performed under warranty at 87,000 miles in 2005.  The original lift pump never missed a beat.  The converted in-tank lift pump operated at 6 psi at idle and 3 psi at wide open throttle.  I drove it that way for over 150,000 miles with a Smarty tuner added.  I replaced the in-tank lift pump with a frame mounted used FASS pump (a low volume one) at 250,000 miles on the truck.  I did this only because I wanted an easy roadside repair in case the lift pump failed.  The FASS lift pump operates at 12 psi at idle and 5 psi wide open throttle.  That lift pump has been operating for over 4 years and 90,000 miles.  I now have over 250,000 miles logged on the rebuilt VP44.  I expect that I can have a VP44 pump failure at any time now, but I will not complain about the service life and I will not blame it on the lift pump.

 

 

- John

 

 

 

For some reason not all vp44s will operate without a lift pump. Don’t know why but without lift pump my truck starts to run rough and dies. 

[Tractorman]

28 minutes ago, Royal Squire said:

For some reason not all vp44s will operate without a lift pump.

 

I made no mention of running a VP44 without a lift pump.  But since you mentioned it, some VP44 engines will continue to run normally even if the lift pump fails.  For that to happen, the lift pump must have a free flow check valve internally and the failure must not block any flow.  If the conditions are right, the internal vane pump in the VP44 continues to draw fuel from the tank.

 

If the failed lift pump does not have an internal free flow check valve or the failure blocks fuel flow or introduces air, the engine will likely stumble or not run at all.

 

- John

[ColoradoColt]

Just ordered this morning. Anyone have any problems with these? I was reading that it replaces the factory fuel filter housing? 

[Joe_Pool]

Disregard this response, I missed that you already ordered a pump. Another option FASS Titanium 95gph.

 

Edited June 22, 2020 by Joe_Pool
To add information

[Mopar1973Man]

Like myself I've had a long conversation with Michael Fabian (Facebook member) the conversation gone on for over 3 hours discussing about VP44 and fuel system design and how to improve. We both agree that fuel pressure is optimal for 99% of people here for 14 to 20 PSI. There is nothing to gain above this. There is lots to lose for fuel pressure below 14 PSI. I know several have mention how they ran 5 to 10 PSI without any problems but the life span typically end up being shorten from low pressure. 

 

Being I've actually check that when the pressure is below 14 PSI the overflow starts to close and then its completely closed at 10 PSI. The extra cooling and lubing will end at 10 PSI. The 10 to 14 PSI may vary from valve to valve a bit but the cooling and lubing does slow way down in the range and stops for the most part at 10 PSI.

[01cummins4ever]

3 hours ago, ColoradoColt said:

Just ordered this morning. Anyone have any problems with these? I was reading that it replaces the factory fuel filter housing? 

If you have the factory fuel heater in the factory canister,  you can run it in conjunction with the new fass, If you live in the cold winter country it might be worth keeping, 

[dripley]

I run my AD in conjunction with the stock filter also. If go this route you will need to get a big line kit formberween the filter and the VP. The oe banjo fittings are quite restrictive.

 

On the truck running after lift pump failure, my oe went out and shut the truck down. It would not fire off. When original AD pump and with the second AD pump failed it was not noticeable while driving. I dont know how long I drove it either time with a failed pump. Out of necessity I had to drive the truck during failures until a replacement arrived and I could install it. While I babied it you could tell no difference in how the motor ran. I was however not babying the the truck until I noticed 0 fuel pressure.

 

About year after Dodge installed an in tank pump on my truck I started havis dead pedal issues. Took to a local shop and the only they found low fuel pressure. 5psi at idle and near 0 at WOT. I installed a booster pump on the frame rails that brought the pressure up and the isuue was gone for a long time. I also dont know how much it brought it up because I had no FP gauge.  Just did not know much about it then. 

[CUMMINSDIESELPWR]

if you get a mechanical, go fuel boss, cant go wrong and about the same price or so as the electrical ones. im not up to speed on the electrical lift pumps so others can chime in. both have their pros and cons.

[ColoradoColt]

12 hours ago, CUMMINSDIESELPWR said:

if you get a mechanical, go fuel boss, cant go wrong and about the same price or so as the electrical ones. im not up to speed on the electrical lift pumps so others can chime in. both have their pros and cons.

I had already ordered a new pump which should be here today, but I looked up fuel boss pumps and this is the message I keep finding....”Note on Fuel Boss availability: At this time we do not have an ETA on the Fuel Boss kits. Unfortunately the pump manufacturer closed due to the pandemic and we don't know when (or even if) they will be reopening.”

[Bullet]

14 hours ago, CUMMINSDIESELPWR said:

if you get a mechanical, go fuel boss, cant go wrong and about the same price or so as the electrical ones. im not up to speed on the electrical lift pumps so others can chime in. both have their pros and cons.

I mostly agree with this except for the very last part.  I have yet to discover a con of the mechanical pump.  But there's really no contest between the two.  I can't believe they are the same price...the electric would have to be 1/3 the price of the mechanical for me to even consider it...and that's the only way I would consider it. 

 

I have the Fuel Boss and it is awesome but DAP has the Assassin pump on sale for $525 and Powerdriven Diesel sells a nice mechanical also.

 

The unavoidable fact is that at some time in the future your $580 electric pump will fail again and risk taking your VP with it.  Their warranty is great about replacing their pump failure but doesn't do anything to help your VP if it gets taken out at the same time.  That's on your nickel.  Once you get a new replacement pump you will have some time elapse before the problem happens again and again...no thanks.  The mechanical pump is more of a permanent solution. 

[wil440]

7 minutes ago, Bullet said:

DAP has the Assassin pump on sale for $525

Assassin on my truck.... no problems with it or the install