She's dead. And I'm done with it.

Ravewolf · September 26, 2023

Well, pretty sure my truck ate it's last injection pump. Left me stranded in my home town. Parked it at my dads house so it's safe, but I'm done with the vp44. And the truck in general. I hated the tan interior on it, and the fact I couldn't find anything other than dash parts for it.

I have a lock on an 86 square body with a junk 350 and axles. As soon as I can get that pile of crap dodge back home, it's getting ripped apart, and parts are going on that Chevy, minus the electric crap.

I'm so over the wires and stuff, just want to p-pump it and never have to worry about it again. And having a truck which I can pretty much build out of a magazine. I always wanted another square, and a cummins one at that. And hopefully the new job I'm getting will make all that possible.

So what's the going rate on a used quadzilla? And a good rebuilt engine pcm? Just had it rebuilt last April at the price of $700. I'm hoping thoroughbred diesel will take a dead vp as a core because they want $1k for a core on top of the $1300 for a mechanical pump.

I'm also selling the transmission and transfer case in lieu of a 4r100 and an np205. With dodge axles. Transmission was rebuilt in 2019 by Super Stick transmission and I babied it because I didn't want to blow it up.

Mopar1973Man · September 27, 2023

Personally I wouldn't do a p-pump on any 24V. I've seen too many trucks converted that end getting parked. Several members here have converted and end up parking the truck. So many things you'll lose and other problems you'll never really over come.

Ravewolf · September 27, 2023

1 hour ago, Mopar1973Man said:

Personally I wouldn't do a p-pump on any 24V. I've seen too many trucks converted that end getting parked. Several members here have converted and end up parking the truck. So many things you'll lose and other problems you'll never really over come.

I'm doing it because I refuse to buy a new vp44 and have to worry about it taking a crap and not getting it warrantied because of the programmer. And what problems? I've been studying this for a while now, and it doesn't seem like it's that hard to do other than tuning,time,and money. Crazy Carl sells a complete kit minus the pump. The vp44 is a giant pile of crap and I'll never run one again. This truck has failed me twice because of it. I also refuse to leave it in that pos dodge body because everything is falling apart on it.

JAG1 · September 27, 2023

9 hours ago, Ravewolf said:

I'm doing it because I refuse to buy a new vp44 and have to worry about it taking a crap and not getting it warrantied because of the programmer. And what problems? I've been studying this for a while now, and it doesn't seem like it's that hard to do other than tuning,time,and money. Crazy Carl sells a complete kit minus the pump. The vp44 is a giant pile of crap and I'll never run one again. This truck has failed me twice because of it. I also refuse to leave it in that pos dodge body because everything is falling apart on it.

Do you know for a fact that these failed VP44's you bought came from a Bosch certified rebuilder? I'm thinking that's your problem as many rebuilders do not follow bosch requirements. One is The clean room and hepa filter system cost millions to build a proper building and set it up. Another is to always replace the computer board on top.

Many of us are not having problems at all with a certified rebuilt VP.

Ravewolf · September 27, 2023

1 hour ago, JAG1 said:

Do you know for a fact that these failed VP44's you bought came from a Bosch certified rebuilder? I'm thinking that's your problem as many rebuilders do not follow bosch requirements. One is The clean room and hepa filter system cost millions to build a proper building and set it up. Another is to always replace the computer board on top.

Many of us are not having problems at all with a certified rebuilt VP.

Well, it's hard to swap a 24v cummins into a Chevy (which I'm hell bent to do) and keep the wiring and such. The simpler the better, unless someone makes a standalone harness, or knows how to make one.

JAG1 · September 28, 2023

8 hours ago, Ravewolf said:

Well, it's hard to swap a 24v cummins into a Chevy (which I'm hell bent to do) and keep the wiring and such. The simpler the better, unless someone makes a standalone harness, or knows how to make one.

A certified rebuilder has to have a 250,000 dollar test stand and run the rebuilt units for, I believe 3 hours, and only the ones functioning perfectly are sold to the public.

Mopar1973Man · September 30, 2023

For the most part correct. The Bosch 815 test stand is about $600k dollars for one stand which does take 3 hours to test and calibrate the New PSG unit on top.

If a vendor will not tell you where your pump was rebuilt and if the rebuilder is a Bosch Certified I would not buy a pump from them no matter how cheap they can make the price. I still see a lot of this going on where places are selling super cheap pumps that seem like they are good rebuilds but fail shortly after warranty. This is why I ask any vendor I deal with...

"Where is the pump rebuild with what company?"

"Is this shop a certified Bosch Rebuilder with a test stand in the shop?"

I can say since I ask questions and only buy a quality pump that has been on the test stand I've seen my pumps last like OE was barely 48k miles. The second Pump I got from the warranty of the Dodge dealer lasted another 243k miles after the AirDog 150 fuel pump. Now I bought a 3rd pump from Diesel Auto Power some time ago during my Mom's medical problems. I'm still on that pump to this day. I'm now at 470k miles and getting ready to land on earth after a trip to the moon and back. (Total distance is 476k)

VP44 is rock solid pump only if you take care of the things below that could kill a VP44...

1. Good fuel pressure and volume - 14 PSI to 20 PSI to keep the overflow valve open to keep the VP44 PSG electronics cooled and the mechanical stuff lubed up with fresh cooled fuel. Make sure you not pulling fuel from inside the sender basket it tends to be much hotter than the rest of the fuel being the sender has all the heater fuel from the head.

2. Good Filters or double stacking - Like myself, I've got an AirDog 150 and got a 3-micron filter on the AirDog, and running a 7-micron NAPA filter in the stock fuel filter can. This catches more debris than anything. Being I'm not pumping from the sender basket my filter last much longer at close to 60k to 70k miles on a filter change.

3. Good Lubricity - This is where the 2 Cycle Oil Theory got started being the LSD diesel was being replaced by ULSD diesel which the lubricity dropped to as low as 636 HFRR and Bosch requires <460 HFRR to be non-damaging. The US made the standard ~520 HFRR which is still too low. If you add a 128:1 ratio of 2 cycle oil to the fuel you'll reduce pump wear. 2 cycle oil was tested and came out at roughly 380 to 400 HFRR in the score. So this passes even Bosch requirements. Please do not use solvent-styled additives (Xylene which is a common Pour Point Depressant) like cetane boosters or anti-gel products. These tend to reduce the lubricity and I highly do not suggest blending cetane boosters or anti-gel with 2-cycle oil. After 22 years of living in Idaho with temperatures as low as -40*F, I've never used anti-gel products ever. Never needed cetane boosters either.

4. Clean Power - Yes if you have not done the W-T ground wire mod I highly suggest you do. AC noise will eat PSG and the ECM fairly quickly. Doing this mod will certainly reduce the chances of the PSG failing on the VP44. Anything over a 0.05 AC volt signal is sign of concern!

Ravewolf · September 30, 2023

1 hour ago, Mopar1973Man said:

For the most part correct. The Bosch 815 test stand is about $600k dollars for one stand which does take 3 hours to test and calibrate the New PSG unit on top.

If a vendor will not tell you where your pump was rebuilt and if the rebuilder is a Bosch Certified I would not buy a pump from them no matter how cheap they can make the price. I still see a lot of this going on where places are selling super cheap pumps that seem like they are good rebuilds but fail shortly after warranty. This is why I ask any vendor I deal with...

"Where is the pump rebuild with what company?"

"Is this shop a certified Bosch Rebuilder with a test stand in the shop?"

I can say since I ask questions and only buy a quality pump that has been on the test stand I've seen my pumps last like OE was barely 48k miles. The second Pump I got from the warranty of the Dodge dealer lasted another 243k miles after the AirDog 150 fuel pump. Now I bought a 3rd pump from Diesel Auto Power some time ago during my Mom's medical problems. I'm still on that pump to this day. I'm now at 470k miles and getting ready to land on earth after a trip to the moon and back. (Total distance is 476k)

VP44 is rock solid pump only if you take care of the things below that could kill a VP44...

1. Good fuel pressure and volume - 14 PSI to 20 PSI to keep the overflow valve open to keep the VP44 PSG electronics cooled and the mechanical stuff lubed up with fresh cooled fuel. Make sure you not pulling fuel from inside the sender basket it tends to be much hotter than the rest of the fuel being the sender has all the heater fuel from the head.

2. Good Filters or double stacking - Like myself, I've got an AirDog 150 and got a 3-micron filter on the AirDog, and running a 7-micron NAPA filter in the stock fuel filter can. This catches more debris than anything. Being I'm not pumping from the sender basket my filter last much longer at close to 60k to 70k miles on a filter change.

3. Good Lubricity - This is where the 2 Cycle Oil Theory got started being the LSD diesel was being replaced by ULSD diesel which the lubricity dropped to as low as 636 HFRR and Bosch requires <460 HFRR to be non-damaging. The US made the standard ~520 HFRR which is still too low. If you add a 128:1 ratio of 2 cycle oil to the fuel you'll reduce pump wear. 2 cycle oil was tested and came out at roughly 380 to 400 HFRR in the score. So this passes even Bosch requirements. Please do not use solvent-styled additives (Xylene which is a common Pour Point Depressant) like cetane boosters or anti-gel products. These tend to reduce the lubricity and I highly do not suggest blending cetane boosters or anti-gel with 2-cycle oil. After 22 years of living in Idaho with temperatures as low as -40*F, I've never used anti-gel products ever. Never needed cetane boosters either.

4. Clean Power - Yes if you have not done the W-T ground wire mod I highly suggest you do. AC noise will eat PSG and the ECM fairly quickly. Doing this mod will certainly reduce the chances of the PSG failing on the VP44. Anything over a 0.05 AC volt signal is sign of concern!

I have a FASS and a ½" fuel line from the pump to the vp44, and I use marvels mystery oil whenever I fill the tank. But since it's the cheaper and easier option, I'll replace the injection pump and I guess put in another filter like you did. What are your thoughts on Blue Chip Diesel? They're super expensive but I'd rather pay a chunk for a unit that'll last the life of the truck. I really want big power though. Not sure if it's feasible with a vp44 unless I spent $4k on a bigger pump.

Like I said I'm fixing to tear the entire truck apart and scrap the body because it's pretty much junk and I don't like it anymore. So I got time to gather parts.

JAG1 · September 30, 2023

I say stay away from Blue Chip they have had problems and reading others concerns/ posts about them I have never heard where they are rebuilt, i.e. from a Bosch certified rebuilder. They are expensive and if you read the reviews and forum talk about them they aren't worth the price. Buy one from Diesel Auto Power, they are good guys and have helped many people that had problems in the past also with a very prompt customer service. I bought newly rebuilt VP44's for both my trucks because the PO did not have good filtration, did not put any two stroke oil in the fuel during break in and may have bought a fake rebuilt unit. No way of knowing but, I bought both mine from Pacific Fuel Injection simply cause they are close to me and are Bosch certified. Both VP's have been flawless. You need to move the draw straw so your not sucking hot fuel back into the VP. Or you move the fuel return to dump down the fill neck as I have done. Eliminate the in tank screens that clog and put on a good pre filter system. I use water seperating pre filters so that any water droplets cannot get emulsified into the fuel by the lift pump, which makes it impossible for the water/fuel separation process by the secondary factory filter.

Don't even think about installing a new rebuilt VP until you have a good W/F separator before the lift pump. This is important!

Edited September 30, 2023 by JAG1

Mopar1973Man · September 30, 2023

57 minutes ago, Ravewolf said:

I use marvels mystery oil whenever I fill the tank.

Bad product. Marvel Mystery Oil Rated at 678 HFRR score which is not an improvement at all.

1 hour ago, Ravewolf said:

What are your thoughts on Blue Chip Diesel?

I'm on the side of I don't trust Blue Chip being he does sell used PSG units. A certified rebuilder can't sell a used PSG.

Andyba20 · September 30, 2023

5 hours ago, Mopar1973Man said:

- 14 PSI to 20 PSI to keep the overflow valve open

Mike, I thought this was debunked by @Tractorman a while back. Meaning lift pump pressure has no say in when the overflow valve is open.

Mopar1973Man · September 30, 2023

It does because of volume of the bigger pumps like AirDog or FASS. Remember you only burn rough between 0 and 10 GPH. The rest of the volume of fuel is return as long as there is 14 PSI or more behind the overflow valve. I'm running 14 to 20 PSI. AirDog 150 base with a AirDog 165 pump (4G). Big part of the return happens at the AirDog but since fuel is making multiple passes the fuel gets polished in the 3micron filter on my AirDog.

Typical VP44 will last about 250k to 350k miles.

Tractorman · October 1, 2023

3 hours ago, Andyba20 said:

Mike, I thought this was debunked by @Tractorman a while back. Meaning lift pump pressure has no say in when the overflow valve is open.

"The lift pump has no say in when the overflow valve is open." I stand behind that statement.

Rarely, does anyone talk about the role of the internal vane pump inside the VP44. Its role is far more important than the role of the lift pump. The only job required of the lift is to always provide a positive pressure at the VP44 injection pump inlet under all operating conditions. The role of the internal vane pump is to supply a flow of fuel (based on engine rpm) to all internal injection pump working components, to the injectors, and to the fuel tank via flowing fuel through the 14 psi overflow valve. The minimum pressure for the internal vane pump regulating valve is 120 psi.

The internal vane pump is a fixed displacement pump. When a fixed displacement pump is operating, it is ALWAYS displacing the SAME volume of liquid at a specific rpm, regardless of whether its inlet is being charged with a lift pump, or it is drawing directly from a fuel tank. This volume cannot be changed without changing the rpm of the engine. It's physically impossible. All fuel must pass through the internal vane pump; there is no path around it. The rpm of the vane pump determines the volume of fuel flow.

As soon as the engine starts and idles, fuel immediately begins to flow at about 18 gph through the 14 psi overflow valve, regardless of lift pump pressure. As engine rpm is increased, fuel flow through the overflow valve increases immediately.

1 hour ago, Mopar1973Man said:

It does because of volume of the bigger pumps like AirDog or FASS. Remember you only burn rough between 0 and 10 GPH. The rest of the volume of fuel is return as long as there is 14 PSI or more behind the overflow valve.

I disagree.

If an engine at idle is sending 18 gph through the overflow valve (returning to tank) and the injectors are consuming 1 gph, then 19 gph are entering the inlet of the VP44's internal vane pump, regardless of lift pump pressure. If a 100 gph lift pump is providing fuel to the VP44 inlet, this means that 81 gph are being returned to the inlet of the lift pump (or to the fuel tank from the lift pump, if a dedicated return line is being used), and the other 19 gph are flowing into the VP44 injection pump.

If a 150 gph lift pump is being used, then 131 gph are being returned from the lift pump and the same 19 gph are flowing into the VP44 injection pump. In both cases , fuel volume flowing into the VP44, fuel volume consumed by the injectors, and fuel volume returning to the fuel tank via the overflow valve remain unchanged.

Back in April of 2001, some members of the TDR performed some extensive testing with the use of a flow meter in the fuel return line circuit from the VP44. Many tests were done - all tests were done at engine idle, cruising speed, and wide open throttle. Tests were done with different lift pumps and different tuning levels. EVERY test showed the same results - 18 gph at idle, 24 gph at cruising speed, 30 gph at wide open throttle. One of the tests even had 0 psi lift pump pressure at wide open throttle, but the fuel return flow remained unchanged. By the way, the maximum lift pump pressure recorded for ALL of the testing was 11 psi - and that was at idle.

Three years ago I performed some fuel return flow tests on my truck. I didn't have access to a flow meter, so I used a container that showed graduated volume measurements.

At idle ....... lift pump pressure 12 psi, return flow from VP44 - 19 gph

A 2000 rpm.... lift pump pressure 8 psi, return flow from VP44 - 28 gph

I repeated the tesst with VP44 pulling directly from the fuel tank (no lift pump). Fuel return flows were exactly the same. I even drove a 28 mile round trip to town without the lift pump in operation. No performance issues whatsoever.

My replacement VP44 has now logged just over 294,000 miles - all of the miles with 12 psi or less lift pump pressure. Most of the miles with less than 6 psi. So, yes, I stand behind what I am saying here.

I don't expect others to accept this information at face value. But, so far, I have yet to hear of any documentation that shows that lift pump pressure must always be over 14 psi in order for fuel to return to the tank from the VP44.

- John

JAG1 · October 1, 2023

@Tractorman who did you buy your VP44 from, since it's such a good one? Also what filters are you using? Thank you in advance. :thumb1:

**Max Tune** · October 1, 2023

Does anyone know why there is a 14 lb valve? What is its purpose? I completely agree with what you're saying, as long as there is positive pressure to the VP, it will have no problems. Positive pressure guarantees no suction or cavitation problems. What I don't understand is why only a 14 lb valve. That fact makes what moparman says understandable. If, with the VP not turning, anything over 14 lbs would cause a return flow to the tank through the pump and anything less would just be pressure against the pump, then I would see the logic behind fuel flow to cool the pump. If no fuel will flow through the 14 lb valve unless the pump is running, then what tractorman says makes sense, but doesn't explain the 14 lb valve if the minimum internal valve is 120 lbs. Both sides make total sense, but which one is actually right?

Tractorman · October 1, 2023

33 minutes ago, JAG1 said:

who did you buy your VP44 from, since it's such a good one? Also what filters are you using? Thank you in advance

I will never know. The VP44 was replaced in June of 2005 (at 87,000 miles) under warranty. At that time I didn't know much about the VP44 fuel system, so I never asked any questions about the pump. Ironically, initially I was disappointed that it was a re-manufactured pump. I wanted a new one. However, over the next few months I learned a lot about the VP44 pump and about some of the inferior components inside the pump. It was then I was glad to have received a re-manufactured pump, mainly because of the many improvements done as time went on.

As far as filter, I just use the stock filter housing and usually a Napa filter. I have added a 140 micron strainer at the suction of the frame-mounted lift pump.

- John

Tractorman · October 1, 2023

@Max Tune, I really appreciate your response. You ask many good questions. The VP44 fuel system is made up of several series and parallel circuits, especially inside the VP44. That's where the complexity begins. Over the years many observations and decisions about how the VP44 works and how it is cooled have been based upon the only two pressures readings available - lift pump pressure and overflow valve pressure (14 psi). Nothing has been based on flow, mainly because no one really seems to know what the flow is in the various parts of the circuit.

10 hours ago, Max Tune said:

Does anyone know why there is a 14 lb valve? What is its purpose?

The 14 psi overflow valve ensures an even distribution of charge pressure to the fill chamber of the high pressure pump (radial piston design) when the fuel solenoid valve is de-energized. The 14 psi is also a low enough pressure that it easily accommodates returning fuel back to the tank without adding excessive heat to the fuel.

10 hours ago, Max Tune said:

If, with the VP not turning, anything over 14 lbs would cause a return flow to the tank through the pump and anything less would just be pressure against the pump, then I would see the logic behind fuel flow to cool the pump.

This is where some of the confusion lies. The workings of the inside of the VP44 are no different than a sophisticated hydraulic system. All hydraulic systems have calibrated internal leakage for lubrication for every component used inside the system.

The inside of the VP44 is no different - it just uses fuel instead of hydraulic oil. Some of those internal components are: positive displacement vane pump, timing piston, timing piston control valve, high pressure injection pump, etc. All of those components are designed with a specific amount of internal leakage for lubrication.

With that said, if the VP44 pump is not turning and lift pump pressure is applied, flow will eventually get to the overflow valve. BUT, the overflow valve will not open. The fuel will exit through the tiny orifice just below the overflow valve, acting as a vent. There will only be a continuous dribble. The dribble will be smaller if there is only 10 psi lift pump pressure. It will be larger if there is 20 psi lift pump pressure, BUT, AGAIN, the overflow valve will not open. The most important thing to note here is, the fuel is NOT being pushed through the internal vane pump. It is leaking through all of the internal components at the calibrated leakage rate. The total leakage rate flow is what will be passing through the orifice vent. Knowing how this works will help in understanding how air is vented from the VP44 after a fuel filter change.

10 hours ago, Max Tune said:

If no fuel will flow through the 14 lb valve unless the pump is running, then what tractorman says makes sense, but doesn't explain the 14 lb valve if the minimum internal valve is 120 lbs.

This part is the hardest part for me to explain, partly because I don't fully understand it myself and partly because it is complex. Refer to the photo below as I try to get through this.

You will note that when the fuel first enters the VP44, it goes right to the inlet of the internal vane pump (Bosch calls this pump the "feed pump"). Note that the fuel leaving the feed pump has three paths to take. All of these path see the regulated pressure.

1. directly to the feed pump pressure regulator (120 psi approximately)

2. to the accumulator (to the far right (rectangle symbol shown with spring)

3. to the timing piston control valve and timing piston (to the right and down)

Now focus on the path after the fuel leaves the accumulator. Here's is where things get complicated. The following is my interpretation of how this system works. The fuel has to pass through the rotor shaft (a small passageway) in order to get to the fill chamber of the high pressure pump. This restriction is why the feed pump pressure falls considerably at this location and the fuel will be subjected to the 14 psi overflow valve pressure as the fuel enters the fill chamber when the fuel solenoid is de-energized. As soon as the fuel solenoid valve energizes, the fill chamber and overflow valve will be isolated from the feed pump / accumulator circuit. When the fuel solenoid de-energizes, the accumulator will absorb the energy left over from high pressure injection and the 14 psi overflow valve will ensure a uniform fill pressure for the next event.

Feel free to pick this apart.

- John

Edited October 1, 2023 by Tractorman
minor content change

**Max Tune** · October 1, 2023

Nothing to pick apart. Thank you for the very thorough explanation. It makes better sense to me now. Thanks again.

**wil440** · October 1, 2023

19 hours ago, Tractorman said:

"The lift pump has no say in when the overflow valve is open." I stand behind that statement.

Rarely, does anyone talk about the role of the internal vane pump inside the VP44. Its role is far more important than the role of the lift pump. The only job required of the lift is to always provide a positive pressure at the VP44 injection pump inlet under all operating conditions. The role of the internal vane pump is to supply a flow of fuel (based on engine rpm) to all internal injection pump working components, to the injectors, and to the fuel tank via flowing fuel through the 14 psi overflow valve. The minimum pressure for the internal vane pump regulating valve is 120 psi.

The internal vane pump is a fixed displacement pump. When a fixed displacement pump is operating, it is ALWAYS displacing the SAME volume of liquid at a specific rpm, regardless of whether its inlet is being charged with a lift pump, or it is drawing directly from a fuel tank.   This volume cannot be changed without changing the rpm of the engine. It's physically impossible. All fuel must pass through the internal vane pump; there is no path around it. The rpm of the vane pump determines the volume of fuel flow.

As soon as the engine starts and idles, fuel immediately begins to flow at about 18 gph through the 14 psi overflow valve, regardless of lift pump pressure. As engine rpm is increased, fuel flow through the overflow valve increases immediately.

I disagree.

If an engine at idle is sending 18 gph through the overflow valve (returning to tank) and the injectors are consuming 1 gph, then 19 gph are entering the inlet of the VP44's internal vane pump, regardless of lift pump pressure. If a 100 gph lift pump is providing fuel to the VP44 inlet, this means that 81 gph are being returned to the inlet of the lift pump (or to the fuel tank from the lift pump, if a dedicated return line is being used), and the other 19 gph are flowing into the VP44 injection pump.

If a 150 gph lift pump is being used, then 131 gph are being returned from the lift pump and the same 19 gph are flowing into the VP44 injection pump. In both cases , fuel volume flowing into the VP44, fuel volume consumed by the injectors, and fuel volume returning to the fuel tank via the overflow valve remain unchanged.

Back in April of 2001, some members of the TDR performed some extensive testing with the use of a flow meter in the fuel return line circuit from the VP44. Many tests were done - all tests were done at engine idle, cruising speed, and wide open throttle. Tests were done with different lift pumps and different tuning levels. EVERY test showed the same results - 18 gph at idle, 24 gph at cruising speed, 30 gph at wide open throttle. One of the tests even had 0 psi lift pump pressure at wide open throttle, but the fuel return flow remained unchanged. By the way, the maximum lift pump pressure recorded for ALL of the testing was 11 psi - and that was at idle.

Three years ago I performed some fuel return flow tests on my truck. I didn't have access to a flow meter, so I used a container that showed graduated volume measurements.

At idle ....... lift pump pressure 12 psi, return flow from VP44 - 19 gph

A 2000 rpm.... lift pump pressure 8 psi, return flow from VP44 - 28 gph

I repeated the tesst with VP44 pulling directly from the fuel tank (no lift pump). Fuel return flows were exactly the same. I even drove a 28 mile round trip to town without the lift pump in operation. No performance issues whatsoever.

My replacement VP44 has now logged just over 294,000 miles - all of the miles with 12 psi or less lift pump pressure. Most of the miles with less than 6 psi.   So, yes, I stand behind what I am saying here.

I don't expect others to accept this information at face value. But, so far, I have yet to hear of any documentation that shows that lift pump pressure must always be over 14 psi in order for fuel to return to the tank from the VP44.

- John

I have a crank driven mechanical lift pump, 6 psi at idle and around 20psi at anything over 2000rpm fuel goes back to basket, not checked the GPM as not got a flow meter but it's LOTS even at idle to the point of what is going back is stirring whats in the tank that much that I don't ever have a problem with hot fuel, worst it gets is pretty close to air temp, maybe a few degrees higher I've even got the filler neck return all made but never bothered to fit it, and not even 1/2" lines.

I've been stuck in traffic after a long drive where the engine is hot and idling for a long time at 6 psi FP and the fuel temp does not increase much at all

I was at first rather concerned about 6psi at idle when I fitted my LP but I don't bother at all now since I checked the return and if I restrict the return which I did once for a VERY short time I got well over 40psi so I believe fuel PSI is just measuring the restriction in the system, fuel flow is the important bit

And don't forget over here in the UK and Europe the VP has a long history and isn't that bad at all, the main vphere is a 4 cylinder but the pump is basically the same, more knowledge of the 4 cyl vp here, pretty sure all fuel inj shops here would have the equip to build them but maybe not so much the 6cyl pump, I've asked at the fuel shop I use and they said no problem so if mine ever fails I'll drop it into them

Andyba20 · October 1, 2023

This site is the premier 2nd Gen site for specific knowledge and content related to these trucks, so it’s important to have updated best practices, especially when we have evidence that changes long held help beliefs. I feel the same way about greasing the wheel bearings through the abs port. It shouldn’t even be a debate anymore…

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