So on my way to work this morning I noticed my pedal was for the most part dead. No acceleration and the engine was "missing" for lack of a better term.

 Made it to work, truck idled smooth like any other day but if revved a few times it would begin to miss again.

 Had the OBD scanner in the truck so plugged in and saw the P0216 code. That was the only code present.

 I know this is the VP death code but before I drop big $$$ on a pump, is there anything else I need to look at? I want to properly diagnose this and not just throw money at it. Can't afford that rout right now.

 Thanks in advance......

I get what you are saying. I wonder if there's any benefit to run a pressure bleed off line back to the tank, allowing more flow Like a 'T' fitting to the outlet side of the L/P since I have Raptor 150's. ? That would help the filtering as well.

 To continually filter you would have to go from tank-filter-pressure regulator w/return-vp44. Which would be more work than just installing an airdog that (if I understand it correctly) already does the same thing.

Since the word “cavitation” has been used a few times in this thread, I thought I would clarify the meaning of “cavitation”, specifically “pump cavitation”.

 

When the suction pressure of a pump becomes so low (usually far below atmospheric pressure), a condition can exist in which part of the fluid being pumped will change from a liquid state to a vapor state where the extremely low pressure exists.  When this vapor is carried to the discharge side of the pump, the pressure will instantly rise above atmospheric pressure and the sudden collapse of the fluid from the vapor state to a liquid state will be so severe that an implosion will occur at a precise and repetitive location.   If the cavitation condition continues, then the implosions will continue to hammer the internal pump parts at that specific location and this repetition will likely cause damage to the internal metal surfaces of the pump at that location.

 

@ddmk6posted, “Pre-filters can and will effect flow and possibly cause cavitation.  Just my opinion but something to think about.” 

 

I think his concern is very valid, especially for the lift pump that uses a separate fuel line to return to the fuel tank.  The higher volume of fuel flowing through the suction circuit of this type of lift pump makes it more susceptible to cavitation.

 

The illustration below represents my estimation of how the VP44 lift pump system is working under a specific engine load.  I think it is a reasonable evaluation based on what I have learned and testing I have done over many years.

 

The following is worth noting about two different lift pump circuits that have identical flow rates, but each has a different return flow circuit design, thus making each pump perform differently in the suction side circuit:

 

·        Lift pump A flows28 gph from the fuel tank through the 140 micron strainer to the lift pump inlet.

·        Lift pump B flows 100 gph from the fuel tank through the 140 micron strainer to the lift pump inlet.

 

If both lift pump A and B have a partially plugged strainer, then lift pump B has a higher potential for cavitation than lift pump A, simply because there is almost 4 times the fuel flow through the fuel strainer for the same engine operating conditions.  Also, lift pump A circuit doesn't really need larger suction lines, but lift pump B circuit does need larger suction lines.

 

 

 

 

 

 

 

@Mopar1973Man stated, “Pumps without a return line are very common for cavitation especially when the pump is dead headed.”

 

I am not sure that I agree with this, mainly because I am not sure that “cavitation” is really occurring under this condition.

 

Many times, the word “cavitation” is misused when describing pump operation – even by professionals.  For example, there are many conditions that can cause aeration in the fuel system.  A lift pump that is passing aerated fuel will likely be noisy, but pump cavitation is not occurring.  The air does not change state from a vapor to a liquid.  The air will compress and decompress, but these events will be relatively harmless to the fuel system.

 

Even if cavitation was occurring under conditions @Mopar1973Manstated, the electric lift pump is never deadheaded under normal starting and operating conditions.  The only time it has a chance of being deadheaded is after a fuel filter change and the lift pump is being used to prime the filters.  Even then, the lift pump is operating at a reduced voltage and is still flowing fuel until the filters are full.  

 

If I made any errors with my numbers, please let me know.

 

- John

                                                                               

Edited January 20, 20223 yr by Tractorman
It's a long post and another correction.

I do believe all of the pumps we're discussing here have an internal pressure regulator that will dump fuel back to the suction side of the pump, so they'll never deadhead. That will, however, put heat into the fuel due to being "churned". Theoretically, that heat could raise the temp enough that the suction side of the pump would be below the vapor pressure of the fuel, this causing real cavitation. But, the fuel does eventually get replaced by cooler fuel.

 

@Mopar1973Man's  recommendation to return fuel outside the basket is the best solution I've seen for hot fuel. A thermostatic diverter valve would be best, but $$$$ is all I've found. I have not yet installed my 3-way ball valve.

4 hours ago, Tractorman said:

Since the word “cavitation” has been used a few times in this thread, I thought I would clarify the meaning of “cavitation”, specifically “pump cavitation”.

 

When the suction pressure of a pump becomes so low (usually far below atmospheric pressure), a condition can exist in which part of the fluid being pumped will change from a liquid state to a vapor state where the extremely low pressure exists.  When this vapor is carried to the discharge side of the pump, the pressure will instantly rise above atmospheric pressure and the sudden collapse of the fluid from the vapor state to a liquid state will be so severe that an implosion will occur at a precise and repetitive location.   If the cavitation condition continues, then the implosions will continue to hammer the internal pump parts at that specific location and this repetition will likely cause damage to the internal metal surfaces of the pump at that location.

 

@ddmk6posted, “Pre-filters can and will effect flow and possibly cause cavitation.  Just my opinion but something to think about.” 

 

I think his concern is very valid, especially for the lift pump that uses a separate fuel line to return to the fuel tank.  The higher the volume of this type of lift pump makes it more susceptible to cavitation.

 

The illustration below represents my estimation of how the VP44 lift pump system is working under a specific engine load.  I think it is a reasonable evaluation based on what I have learned and testing I have done over many years.

 

The following is worth noting about two different lift pump circuits that have identical flow rates, but each has a different return flow circuit design, thus making each pump perform differently in the suction side circuit:

 

·        Lift pump A flows28 gph from the fuel tank through the 140 micron strainer to the lift pump inlet.

·        Lift pump B flows 100 gph from the fuel tank through the 140 micron strainer to the lift pump inlet.

 

If both lift pump A and B have a partially plugged strainer, then lift pump B has a higher potential for cavitation than lift pump A, simply because there is almost 4 times the fuel flow through the fuel strainer for the same engine operating conditions.  Also, lift pump A circuit doesn't really need larger suction lines, but lift pump B circuit does need larger suction lines.

 

 

 

 

 

 

 

@Mopar1973Man stated, “Pumps without a return line are very common for cavitation especially when the pump is dead headed.”

 

I am not sure that I agree with this, mainly because I am not sure that “cavitation” is really occurring under this condition.

 

Many times, the word “cavitation” is misused when describing pump operation – even by professionals.  For example, there are many conditions that can cause aeration in the fuel system.  A lift pump that is passing aerated fuel will likely be noisy, but pump cavitation is not occurring.  The air does not change state from a vapor to a liquid.  The air will compress and decompress, but these events will be relatively harmless to the fuel system.

 

Even if cavitation was occurring under conditions @Mopar1973Manstated, the electric lift pump is never deadheaded under normal starting and operating conditions.  The only time it has a chance of being deadheaded is after a fuel filter change and the lift pump is being used to prime the filters.  Even then, the lift pump is operating at a reduced voltage and is still flowing fuel until the filters are full.  

 

If I made any errors with my numbers, please let me know.

 

- John

                                                                               

This is excellent work @Tractorman.  Every bit of it.

As I mentioned previously, and you touched on here as well, deadheading is an entirely separate issue with its own set of problems.  Those problems are wide ranging depending on pump design and application.  A positive displacement pump obviously isn't going to survive deadheading lol.

Really nice write up.

1 hour ago, LorenS said:

Theoretically, that heat could raise the temp enough that the suction side of the pump would be below the vapor pressure of the fuel, this causing real cavitation. 

The fuel will not heat up until its moving through the restriction (friction), i.e., check valve.  It's not constantly recirculating through the pump and check, it's going into the tank where heat will dissipate. If anything you'll see the pressure difference and temp differences downstream of the check valve.

Edited January 20, 20223 yr by ddmk6

25 minutes ago, ddmk6 said:

it's going into the tank where heat will dissipate

Not if it's deadheaded, as people were discussing.

@ddmk6, I very much appreciate your remarks.  

 

Thank you,

- John

21 minutes ago, LorenS said:

Not if it's deadheaded, as people were discussing.

You were describing it going through a check valve and returning to tank.  That's what I quoted and that's what I commented on.

3 minutes ago, ddmk6 said:

You were describing it going through a check valve and returning to tank.

You're wrong again. Raptors and FASS DRP pumps have only two external connections. Their pressure regulator is internal, dumping fuel back to the suction side of the pump, inside the housing - not clear back to the tank.

Edited January 20, 20223 yr by LorenS

3 minutes ago, LorenS said:

You're wrong again.

Ok.  Your truck, do whatever you want.  You might want to re-read your original comment though.  I was merely trying to help you understand.  If you understood more about pump design, you would know that some pumps can actually run dead headed without consequence....others can not.  Some are designed to flow through a relief valve and return to sump where the heat dissipates prior to recirculation. 

 

This could go on forever but I'm done.

This might muddy the water a bit but there is likely no cavitation going on inside the pump, unless the conditions @Tractorman mentioned are present. When a internally regulating/relieving pump is dead headed, it just gets sent back to the inlet of said pump. All that action on the fuel creates heat and it goes into the pump body and the fuel. Only way to remove the heat is to remove the dead head condition. Then flow through the pump will cool things down. 

 

Fire trucks have a pump to tank line for this reason. Imagine a pump capable of about 50-150+ gallons per minute at engine idle with only like 5-15 psi just sitting there churning the water inside the pump case (rough numbers). Its gonna get hot. Easily hot enough to boil the water inside the pump case. Now, if we open the pump to tank line to move water into the 250-3000 gallon tank as a heat sink, you push off the time to get hot immensely.

 

Pumps and pump setups are a very deep and complicated subject. Turbochargers, superchargers, fuel pumps, oil pumps, water pumps, they all fall under this umbrella. Kinda like saying you have a degree in science.. Can you be more specific?

 

Personally, on my truck, I run a GDP fuel boss with a custom fuel system, including a 2 micron filter and a f/w separator and a fuelab return style fuel pressure regulator. I personally feel that a return style fuel system is the better way of having the plumbing routed. It constantly moves fuel to keep things clean and keeps the flow moving through the pump to keep it cool. I'm not saying this as a be all end all, it's my opinion and nothing more.

Are you saying even though I have Raptor pumps, I could install return style fuel pressure regulators? Simple as installing a 'T' on outlet  line with another 'T' on the existing return line?

 

I appreciate everyone's help/ comments they all help to bounce the thoughts around and come to a much better understanding.

 

Edited January 20, 20223 yr by JAG1

Yes to installing them, but they would take the place of a tee fitting. They are omnidirectional straight through and have a return port on the bottom of the regulator.

 

Just remember with multiple regulators that you will only have as much pressure as the lowest set regulator 

 

Also back pressure plays a big role in operation of regulators so tying into another return line might not be a good idea.. But if the pressures are low enough it might not make a difference.

Mine would be okay as I have an increased size, 1/2'' rubber fuel hose return near the sweated nipple on the fill necks. I like it dumping the return fuel there, I can see it when opening the cap and helps mix the two stroke additive.

 

Now to look for return style fuel pressure regulator. I like the benefits it carries.

Edited January 20, 20223 yr by JAG1

So to muddy the water further, suppose that a small leak on the pump intake causes foaming that's not the same as cavitation. In that case a return line prevents a big air pocket from forming down stream.

On 1/19/2022 at 10:20 PM, ddmk6 said:

I was merely trying to help you understand.

Buddy, I do understand.  Typing on a phone I was less verbose than the below, but it is exactly what I said just with more descriptive words.

 

On 1/20/2022 at 7:52 AM, Silverwolf2691 said:

When a internally regulating/relieving pump is dead headed, it just gets sent back to the inlet of said pump. All that action on the fuel creates heat and it goes into the pump body and the fuel. Only way to remove the heat is to remove the dead head condition. Then flow through the pump will cool things down.

 

 Finally on my way to getting this fixed. I called DAP today and ordered my lift pump. I bought the Raptor 150 that comes with the 1/2" fuel line from the oem filter to the vp. Yhe guy I talked to said it would be fine on the oem fuel lines from the tank for now. Once the weather warms up some I will relocate the pump to the frame and drop the tank for a draw straw and full 1/2" line kit with a pre filter. A fuel pressure gauge will be on that list as well so I can keep an eye on it.

 Just wanted to update what was going on.

2 hours ago, Doubletrouble said:

I bought the Raptor 150 that comes with the 1/2" fuel line from the oem filter to the vp.

 

Does this lift pump have a separate return line for fuel not used?

 

- John

No it does not. I don't believe any factory replacement lift pumps have a fuel return line. Maybe the big air dog or fass systems do. I wasn't looking to spend $700 this time around though.

Okay, that makes sense about what the guy from DAP told you regarding staying with OEM fuel line sizes from the tank to the lift pump.  

 

Just wanted to clarify that even though you will now have a 150 gph lift pump and a 1/2" line to the VP44, no more fuel will be flowing through the VP44 and returning to the fuel tank than when you had the lower gph lift pump.  The VP44's internal fixed displacement vane pump and the VP44's internal fuel routing determines how much fuel will return to the fuel tank.

 

- John