01 24v dead in the water....

[Tractorman]

I believe you are correct.

 

I was being a bit facetious in my previous reply.

 

- John

[Basranabread]

8 minutes ago, Tractorman said:

I believe you are correct.

 

I was being a bit facetious in my previous reply.

 

- John

Gotcha haha, at this point I am just throwing anything I can think of at this truck so maybe I'll swap the pins in the plug tomorrow just because 

[LorenS]

On 2/11/2023 at 9:44 PM, Tractorman said:

AirDog | R1SBU371 | Raptor Pump – Universal 150 GPH

Well there you go! Had no idea this pump exists. Seems like a terrible pump choice for a mostly stock, street driven truck. Just churning that fuel in circles, getting hotter and hotter with each pass through the pump without even a chance to cool off in the tank.

[Basranabread]

So I gathered the appropriate fittings today and removed the quick connect fittings on the suction side tonight. I also rigged up the fuel gauge into the cab of the truck to monitor and took the truck for another test drive. Exact same results. Pressure remained steady on the gauge and all seemed well for the first little bit of getting heat into the truck. Once warm I did a full throttle pull and it actually seemed to act as it should. Pressure stayed steady and truck seemed to have good power. After about another 5 minutes I tried this again and pressure dropped off slowly with throttle application. I pulled over to see if it would recover and it did, very slowly. The needle on the gauge was jumping slightly indicating air ingress or churning and the pump became noisy once again. I shut the truck off and primed the pump a few times and it became quiet. I then started it and drove again, hard throttle acceleration and pressure drops off with a noisy pump. It got so bad on the way home that basically any amount of throttle application and the pressure would fall off slowly so I would pull over to let it recover. As I have gone through everything and mitigated any potential causes of air leaks on the suction side, I don't think I have anything else to blame besides a faulty o ring or something else  with the pump.

[Tractorman]

You could have a faulty lift  pump or you could have a random very restrictive blockage between the fuel tank and the inlet of the lift pump.  I don't think it is air getting into the suction lines. 

 

I am leaning toward the blockage.  There is a fixed displacement vane pump inside the VP44.   With the engine idling, that pump is returning fuel at about 18 gph to the fuel tank via the overflow valve.  Under full rpm the vane pump will return fuel at about 30 gph to the fuel tank.   With the engine off and the lift pump running, very little fuel is returned to the fuel tank because the fuel is being forced around the very small clearances of the vanes in the non-rotating vane pump inside the VP44.

 

I don't think you need to drive the truck to make the symptoms happen.  Try this:  Bring the engine to 2500 rpm and hold it there.  See if the fuel pressure begins to drop like it did on your test drive.  If it does, then perform the following test:

 

*  Run a fuel line from a 5 gallon container filled with clean diesel.  Connect the fuel line directly to the inlet of the lift pump. 

*  Start the engine and let it idle to let the fuel pressure stabilize. 

*  Bring the engine to 2500 rpm and hold it there

 

If the fuel pressure drops slightly, but remains steady at 2500 rpm, then you know you have a suction problem.  If the fuel pressure at 2500 rpm behaves like it did on your test drive, then you know you have a lift pump problem. 

 

If you can't make the symptoms happen, you may have to secure the 5 gallon fuel container in the bed of the truck and drive the truck to duplicate the symptoms.  Just make sure you are being safe.

 

When the lift pump is operating normal, what is the fuel pressure?

 

- John

[Mopar1973Man]

Any pump without a 3rd line for return is going to create cavitation issues. This is why I like the AirDog series. Any air is returned to the tank also the pump is never ran dead head being the pump has a return and can always flow to the tank.

[Tractorman]

4 hours ago, Mopar1973Man said:

Any pump without a 3rd line for return is going to create cavitation issues.

 

A lift pump without a dedicated return line flows 100% of its displacement from its internal discharge location.  What fuel doesn't leave the pump outlet to the VP44 gets returned to its own inlet internally.  There is no cavitation.

 

A lift pump with a dedicated return line also flows 100% of its displacement from its internal discharge location.  What doesn't leave the pump outlet to the VP44 gets returned to the fuel tank.  There is no cavitation.

 

Cavitation only occurs when when the pressure on the inlet side of the lift pump falls so far below atmospheric pressure (usually greater than 15"HG vacuum) that some of the fuel will vaporize (changing from a liquid state to a vapor state) and expand before it enters the lift pump inlet.  When that fuel vapor passes to the pressure side of the lift pump, the fuel vapor will suddenly collapse as it condenses to a liquid state.  That sudden collapse (always in the same location) causes an implosion that is so severe that pieces of metal can be removed repeatedly at the surface of where the implosion occurs.  Any pump can suffer from cavitation if there is a severe restriction on the inlet side of the pump.

 

4 hours ago, Mopar1973Man said:

This is why I like the AirDog series. Any air is returned to the tank also the pump is never ran dead head being the pump has a return and can always flow to the tank.

 

Neither type lift pump is truly deadheaded, even if you block the discharge port - one has an external dedicated return line, the other returns fuel to the inlet internally, but BOTH will flow the same volume fuel over the regulating valve if they are equal displacement pumps.  As far as I know, Air Dog, FASS, and Carter lift pumps are all positive displacement pumps.  They cannot be truly deadheaded- if they are truly deadheaded, the pump will be forced to stop rotating, or a fuse will blow, or something is going to break.

 

And, yes, there are benefits to having a lift pump with a dedicated fuel return line, but cavitation is not one of them.

 

- John

 

 

 

Edited February 14, 2023 by Tractorman

[JAG1]

On 6/20/2022 at 8:44 AM, Basranabread said:

Okay, will do. Not sure if this info gives any indication but the only thing strange I noticed with the truck prior to this was the alarm randomly went off twice with no trigger. Would sound and then would turn itself off after about 30 seconds. This happened two times that I know of in the week prior to my current issue. Just made me wonder about wiring gremlins.

my 01 sometimes goes thru a period when the alarm goes on almost every time I unlock with the key. If I turn the key twice,  so as to unlocking both doors, then the alarm does not go off. Have to remember to do this all the time. Then other times it never gives a problem and everything is back to normal. Sometimes I have to grab the key FOB kept in the door handle and lock and unlock the truck while sitting inside and then it will shut off and allow me to start the truck. Other gremlins is when the overhead will suddenly show 'CCD' but, always goes away on it's own without driveability problems. The W-T ground reference was done to both my 2nd gens and reduced the level of damaging AC ripple in both electrical systems.

 

When I bought my 01 with 190 k it had the intank screens that were approx 2/3rds clogged with dirt. Both trucks have a primary filter before the lift pump on the frame, no screens anywhere but, both have the factory filter. It's a rare condition that sometimes the fuel tank vent can also get clogged and only once did my advice on checking for this proved me correct. Does not hurt to check by simply loosening the fuel cap when you get it running again but, this is most likely an ineffective idea compared to the issues I am hearing.

 

I do not think you have an electrical problem unless it is inside the VP, I think it's fuel related. The frame mounted lift pumps come with a screen placed in the inlet side, unless they stopped doing that, I would remove it with needle nose, remove the in tank screens and install a primary filter that allows changing every 15-30 k miles keeping the system clear and unclogged. You need to do this prior to getting a new VP. the nice thing is not only possibly finding your problem but you've been given the chance to do the best for your fuel system.

 

I did not drive either of my 2 second gen trucks until the screens were removed inside the tank and the inlet screens on the lift pumps. The Raptor 100 served me well until about 60 k miles started to show signs of weakness. By then I bought my O1 and install 150's to each truck. Both lift pumps are seemingly stronger pumps so far. By this time however, I have learned about Tractorman's return flow tests with fuel pressure with his introduction showing lower pressures are okay as long as there is pressure to the VP and having a minimum of positive flow of around 4-5 pounds. I mention this to not get off track but, to include his findings for another day of discussion. Right now your truck is more important.

 

I have only seen one other situation of a no running condition from clogged screens. Owner was surprised when he removed the tank and found it clogged. My 01 was on its way to clogging eventually.

Edited February 14, 2023 by JAG1

[Mopar1973Man]

1 hour ago, Tractorman said:

A lift pump without a dedicated return line flows 100% of its displacement from its internal discharge location.  What fuel doesn't leave the pump outlet to the VP44 gets returned to its own inlet internally.  There is no cavitation.

 

This was proved in video form years ago with a stock Carter lift pumps is you dead head the pump the will cavitate being there is no return. This is due to the recirculation of fuel in the pump body.  Which I wish the video was still up be yes it was creating foam in the fuel. 

 

 

[Tractorman]

I have seen that video.  As I recall, the video does not replicate what is going on in the VP44 fuel system.  In the video I believe the pump outlet is completely blocked forcing all fuel to flow over the regulating valve and return to the lift pump's inlet.  With this condition sustained, I can understand the continuous heat generation will begin to vaporize some of the fuel and cavitation could occur at the inlet.  But, this is not the real life condition that the lift pump is operating in.

 

In the VP44 fuel system, there is always a minimum of 18 gph returning from the VP44 injection pump to the fuel tank and that minimum flow occurs at engine idle.  The internal fixed displacement vane determines that volume.  This means there is always a minimum of 18 gph leaving the outlet of the lift pump on an idling engine.  The fuel that is recirculated within the lift pump housing (over the regulating valve and back to the inlet) is mixed with incoming fuel which will quickly stabilize heat buildup inside the lift pump.  In normal designed operation the heat will not rise to the point of vaporizing fuel, so conditions for cavitation will not occur.  As engine throttle is increased, more fuel will return to the fuel tank, thus more fuel will be leaving outlet of the lift pump, consequently less fuel will be recirculating inside the lift pump housing. 

 

The point that I am trying to make is that the OP has installed a new lift pump that does not use a dedicated return line.  If his lift pump is cavitating, it because there is a restricted suction -  whether it be in the lines, tank, or inside the lift pump - not because there isn't a dedicated return line.

 

The link below gives a good explanation of cavitation vs. aeration.  Only need to view the first couple of minutes for the explanation.

 

https://www.google.com/search?client=firefox-b-1-d&q=airdog+caviatation+video#fpstate=ive&vld=cid:72664d2a,vid:hWeQUDyDEnY

 

- John

 

 

Edited February 14, 2023 by Tractorman
content

[W-T]

These lift pumps we are referring to, are all mechanical Cavity Gear pumps. Most all of us, are familiar with this design and the history in the automotive industry exceeds 50 years or more. Yes, as John @Tractorman has pointed out these are positive displacement pumps and by design they are modest in their ability to manipulate liquid material in a closed environment.  

 

This environment has restrictive characteristics at both inlet (feed point) and outlet (discharge) aspects, that in design, these pumps can over come these resistive road blocks and deliver diesel fuel reasonably well.  However ; the term "reasonably well" has limits due to the modest nature of these Cavity Gear pumps.

These little pumps are great for the purpose they were designed for but....do not expect them to operate in a poorly designed or maintained transfer system. 

 

The ability to draw liquid diesel fuel with these wimpy little pumps requires a clean low restriction feed method,...meaning NO Oatmeal in the screen basket within the fuel tank.

I know...everyone knows this...but, if you can't see your wetted-feed point within the tank, I would suggest inspecting that aspect.

 

Any minor air leak that may not be evident in a cold environment may very well become apparent once the environment changes thermally. Usually fittings with a mated surface for point to point surface contact will prevent liquid seepage but, this same fitting could suck-air and hinder pump operation once the thermal threshold has been met and exacerbates the expansion/contraction coefficient of  the metal components in service.  Air is easier to suck through a straw compared to a milkshake so, the effort to find an elusive air-leak that is so incredibly tiny is a challenge.

 

Avoid the "just tighten the crap out of the fitting" method. Always apply light lubrication to the "mated fitting's" surfaces, prior to mating them and avoid galling the jeweled surfaces.

 

15 hours ago, Basranabread said:

Once warm I did a full throttle pull and it actually seemed to act as it should. 

 

After about another 5 minutes I tried this again and pressure dropped off slowly with throttle application.

 

I pulled over to see if it would recover and it did, very slowly.

 

The needle on the gauge was jumping slightly indicating air ingress or churning and the pump became noisy once again.

 

I shut the truck off and primed the pump a few times and it became quiet.

 

I then started it and drove again, hard throttle acceleration and pressure drops off with a noisy pump.

 

I don't think I have anything else to blame (besides a faulty o ring) or something else  with the pump. What o-ring?

 

@Basranabread I'm only trying for a simple solution, and I appreciate your diligence along with excellent commentary and it is your information that leads me back to the primary observations. It causes me to suspect an air leak. The condition within your fuel tank that can't be seen for verification would be a resistive element.

 

Going back to the modest design of these pumps and how small errors will lead to faulty performance, it is just the nature of this particular design. The system design is providing liquid pressure maximums of 15 to 20 PSI and these characteristics place this style of pump into the "Peanut Whistle" category where very small leakage errors cripple the performance drastically.

 

Your observation of "noisy pump" and once re-primed....goes quiet....tells me it's sucking air.

 

Oh...yeah, what O-ring?....you're scaring me when you placed that into the "what if " equation.

 

Respectfully,

W-T   

[Tractorman]

2 hours ago, W-T said:

I'm only trying for a simple solution, and I appreciate your diligence along with excellent commentary and it is your information that leads me back to the primary observations. It causes me to suspect an air leak. The condition within your fuel tank that can't be seen for verification would be a resistive element.

 

I very much agree with everything you stated.  But, in this case I don't think his symptom is caused by an air leak.  Here is why. 

 

He performed the free flow test into a five gallon bucket.  He reported that the bucket filled to about halfway in one minute.  That volume of fuel coincides with the 150 gph rated flow specification for that particular lift pump.  An air leak would have certainly showed during this test because this would have been the time for air to have been drawn in because this is the only time the lift pump can flow maximum fuel through the suction line, hence the largest pressure drop.  He did not report a stream of air saturated fuel.  And, if the fuel would have been saturated with air,  I don't think the bucket would have been as full.

 

Once the lift pump is reconnected to the fuel system to perform as a normally operating lift pump, it will never flow 150 gph again.  The maximum flow from the fuel tank to the inlet of the lift pump would be less than 50 gph on a stock or mild tune, even if the engine is placed under a demanding load.  This is because even with injectors at max fuel flow and engine at max rpm, the sum of injector fuel consumption (approximately 10 gph) and the return flow from the VP44 (approximately 30 gph) via the internal vane pump would be less than 50 gph. 

 

Also, if enough air is entrained in the fuel to cause loss of engine performance under a load, the engine would likely die when the throttle is released to idle.  At best, the engine would not restart without bleeding some injectors.

 

One more thing to add - in my experience I have always seen lift pump pressure even when there is a fair amount of air in the fuel system.  The lift pump will pump fuel entrained with air quite easily.  It is the fuel injection pump that can't deal with the compressible solution.   @Basranabreadreported a few times that fuel pressure was at "0" psi.  To me, a "0" psi reading is indicative of a restriction on the inlet side of the lift pump, not entrained air.

 

Now, of course, if it turns that his problem is air getting into the fuel system, you can just disregard everything I have posted - consider it as "buffoonery".   I know I will.

 

- John

 

 

Edited February 15, 2023 by Tractorman

[Great work!]

I have to step in here. We have all overlooked a mechanical issue within the pump and jumped into the fluid dynamics. 

The drive mechanism could simply be slipping or partly stripped out. Splines gears, motor shaft , even armature poles slipping could be at fault.

Pumping into a bucket is an easy task, but doing so at a high pressure times volume requires much more work [torque].

Slipping can cause noise and localized heating which can cause the parts to temporarily seize together so it works sometimes. 

 

I found an image online. Different model but probably similar. It has mini rubber isolated coupler as well as splines in the gear rotor.

 

https://lincolndieselspecialties.com/i-23848567-airdog-ii-4g-df-165-lift-pump-2011-2014.html

Edited February 15, 2023 by Great work!
Link to pic.

[Tractorman]

17 hours ago, Tractorman said:

You could have a faulty lift  pump or you could have a random very restrictive blockage between the fuel tank and the inlet of the lift pump.

 

17 hours ago, Tractorman said:

I don't think you need to drive the truck to make the symptoms happen.  Try this:  Bring the engine to 2500 rpm and hold it there.  See if the fuel pressure begins to drop like it did on your test drive.  If it does, then perform the following test:

 

*  Run a fuel line from a 5 gallon container filled with clean diesel.  Connect the fuel line directly to the inlet of the lift pump. 

*  Start the engine and let it idle to let the fuel pressure stabilize. 

*  Bring the engine to 2500 rpm and hold it there

 

If the fuel pressure drops slightly, but remains steady at 2500 rpm, then you know you have a suction problem.  If the fuel pressure at 2500 rpm behaves like it did on your test drive, then you know you have a lift pump problem.

 

@Great work!, you make a good point here.  I did mention a possible lift pump problem in my previous posts.  But, what you say about a poor mechanical connection could certainly match the symptoms.  Good observation on your part.

 

- John

[LorenS]

Does the OP have a means to view fuel temperature? I have a FASS 90-100 GPH pump mounted similarly to the frame and have seen fuel temps over 160 ⁰F on 90⁰ days, just cruising down the interstate for hours at 2000 RPM. The spin on filter ahead of the pump was nowhere near that hot. At 1/3 gallon per minute flow, I can't imagine the stock filter housing transmitted that much heat, so it either came from the VP44 (in which case Mopar1973man would have similar fuel temps and he doesn't) or it comes from the lift pump churning the fuel.

[Tractorman]

@LorenS, I have a similar setup - a frame mounted FASS without a dedicated return line.  Not sure of the volume because it is a used pump, but I think it is about 65 gph.  I know it does heat the fuel some.  I modified my VP44 fuel return line by installing a directional valve to allow fuel to return into the fuel basket during the winter months and to allow the fuel to return into the fuel tank filler neck during the summer months.  I have no way to monitor fuel temperature other than to place my hand onto the lift pump body.  I can definitely tell the difference when I switch the fuel return valve, though.

 

I am fairly certain that Mopar1973Man's lift pump dedicated fuel return line and his VP44 fuel return line return fuel well away from the fuel basket, consequently he runs low fuel temperatures.

 

- John

[Mopar1973Man]

7 minutes ago, Tractorman said:

I am fairly certain that Mopar1973Man's lift pump dedicated fuel return line and his VP44 fuel return line return fuel well away from the fuel basket, consequently he runs low fuel temperatures.

True. My Airdog has the return into the fuel tank filler neck. Injectors and VP44 returns to the sender basket. My draw straw is installed forward of the sender basket and away from both returns. Fuel temp super rare to exceed 140°F.

[LorenS]

I understand the issue of returning to the basket, but I also know that the fuel coming through my strainer on the suction side of my pump is nowhere near 160.

[Tractorman]

There is no doubt that recirculating the fuel inside the lift pump generates heat, but how much heat is only a guess - mainly because we don't get any real specifications for these lift pumps which leave too many variables.  Then we have the fixed displacement vane pump (inside the VP44) with its own regulating valve that returns fuel back to its own inlet - so more heat generation.   I am fairly sure that vane pump doesn't recirculate as much fuel as the lift pump without a dedicated return, but it does recirculate the fuel at a much higher pressure - somewhere between 100 psi to 300 psi.  So, heat will be generated there as well.  Again, how much? 

 

The heat generated from recirculation in both pumps could be approximately calculated IF we had information providing how much fuel was being recirculated at a given pressure in the respective pumps. 

 

The formula I used when I was in the hydraulic industry was gpm x psi / 1714 = hp.  Horsepower would then be converted to watts to represent heat.  Of course, these calculations were done using hydraulic oil, but there still should be some similarities. 

 

So, let's pretend there is 60 gph at 15 psi recirculating inside the lift pump.  Another 20 gph is flowing out the lift pump and through the VP44 and returning to the fuel tank on this idling VP44 engine.     In this example, 60 gph would be 1 gpm, hence 1 gpm x 15 psi / 1714 = .009 hp or 6.5 watts.  That would be 6.5 watts of continuous heat being added to the recirculating fuel inside the lift pump.  But some of that fuel would be mixing with the incoming and outgoing fuel at the rate of 20 gph, consequently carrying some of that heat away.  As engine load and engine rpm increase, more fuel will be demanded by the VP44 internal vane pump and injectors, so lift pump pressure will fall, and less fuel will be recirculated inside the lift pump, which in turn will reduce heat being added to the recirculating fuel.

 

I have no idea how accurate these calculations are, but I think it should at least give some idea as to what is going on.

 

Feel free to punch lots of holes in this line of thinking.

 

- John

[Basranabread]

I have finally had a diagnostic breakthrough this evening! I was preparing to run the truck out of some 5 gallon pails and in doing so I decided to use the lift pump to fill my pails. I removed the outlet line from my filter housing and ran it down to a pail. While running the pump like this it remained noisy and I observed an insufficient amount of fuel coming out. I still wanted to bypass my suction side components to rule out an air leak so continued to use this method to fill the pail enough to use for fuel feed. I then ran an about 24" line from this pail to the suction of the pump and left the discharge line in a second empty pail. I ran the pump for a minute and it only filled the pail a generous 1/4 full. It also remained noisy the entire time during this. The results of this tells me that the pump is faulty. During my test drives I would always follow the same route and drive the truck in the same manor during the drives. Each time I would experience my symptoms in generally the same location. My speculation is that the pump would generate some heat and cause either an oring or seal in the pump assembly to leak air or an already damaged pump to act up. I did also talk to an airdog rep yesterday and he mentioned that the regulator being loose initially could have prematurely damaged the pump and agreed to send me a replacement. I believe after my last test drive the damage to the pump became great enough to cause it to have these issues cold or hot. This would explain why it passed my previous bucket test. So I have a new pump on the way, I will bolt check it and swap them out. Once this is done I will report back either good news or bad but I am very hopeful this will resolve my issues.