Testing Aux Fuel Pump Operation

[glcaines]

Is the draw tube clean and clear? Is the line from the aux pump to the tank clear? Could there be a stuck check valve? Are you able to bench test the old/new pump using short hoses?

Draw tube is clean and clear and the line to the tank is clear. I did bench test both the old and new pumps. Both work fine with short hoses although suction is not a high as I would have thought. Both behave identically. I can blow through the line to the tank with the solenoid valve open.

 

[Daybreak]

Howdy,
Of Note: How long did you operate the aux pump? With all fittings tight, and no leak, it does take a little time to make vacuum to lift and suck fuel.

 

[glcaines]

Howdy,
Of Note: How long did you operate the aux pump? With all fittings tight, and no leak, it does take a little time to make vacuum to lift and suck fuel.

I've let it run as much as one hour.

 

[CapePrep]

It appears you have really put in effort to eliminate all possible reasons for this. But, there is something still missing. There is no way it should take that long. I literally waited maybe 30 seconds for mine to prime and pump. I wish I had an answer for you. Have you checked the voltage to the pump when running? Pump not running at proper speed? This is quite the dilemma, I hope we can find the reason so that we can help others in the future.

I've let it run as much as one hour.

 

[Chainbreaker]

There's gotta be a reason we are somehow overlooking. So, lets try a different angle looking at this issue. What about the output line? Any chance its restricted making it that much harder with the longer suction line to push diesel through outlet aux output feed line to fuel tank?

 

[Chainbreaker]

Just trying to think out of the box again... What is the pump mfg # of both the old and new aux pump as compared to OEM pump # in TM? Any chance the wrong pump was installed before you got it and when you replaced it you copied the mistake? I know there are various pump models that look the same but don't have the correct PSI spec's as what is called for. Not knowing the history of your unit, could it be that someone before you may have replaced it with one that looked the same but was a lower psi model and thus priced cheaper so they bought it?

Edit: I believe this is the most current available fuel pump for MEP-002a/-003a: https://www.pegasusautoracing.com/productdetails.asp?RecID=8850

FYI- Here is how you locate/identify the P/N on these series Facet pumps, although very hard to see if painted or rusted: https://www.pegasusautoracing.com/document.asp?DocID=TECH00023

 

[glcaines]

It appears you have really put in effort to eliminate all possible reasons for this. But, there is something still missing. There is no way it should take that long. I literally waited maybe 30 seconds for mine to prime and pump. I wish I had an answer for you. Have you checked the voltage to the pump when running? Pump not running at proper speed? This is quite the dilemma, I hope we can find the reason so that we can help others in the future.

Definitely has proper voltage at pump when running and also when I jumpered the pump directly to the batteries.

 

[glcaines]

Just trying to think out of the box again... What is the pump mfg # of both the old and new aux pump as compared to OEM pump # in TM? Any chance the wrong pump was installed before you got it and when you replaced it you copied the mistake? I know there are various pump models that look the same but don't have the correct PSI spec's as what is called for. Not knowing the history of your unit, could it be that someone before you may have replaced it with one that looked the same but was a lower psi model and thus priced cheaper so they bought it?
Edit: I believe this is the most current available fuel pump for MEP-002a/-003a: https://www.pegasusautoracing.com/productdetails.asp?RecID=8850
FYI- Here is how you locate/identify the P/N on these series Facet pumps, although very hard to see if painted or rusted: https://www.pegasusautoracing.com/document.asp?DocID=TECH00023

Definitely the correct pump for both original and new. I ordered a new FACET 480517E pump from Yacht Supply Depot as they had the cheapest price I could find. Both pumps produce the specified PSI on the output side when using short input tubing to diesel supply. This hasn't been a significant problem for me since it is quite easy for me to have my secondary diesel supply at the same or higher level. I'm pulling from a John Deere 5520 tank or from one of my deuce fuel tanks. However, there is definitely something wrong that baffles me. I have the ability to fill the aux fuel line, including the dip tube, seal both ends and pressurize to around 25 PSI with a pressure gauge attached. I'll thoroughly wash the exterior with Dawn dish detergent. I'll be able to see if the pressure drops and look for wet areas on the hose and connectors. I've already pressurized the hose with air and looked for bubbles when soapy water was applied to the outside and it passed that test. I'm very stubborn - I intend to find the cause. Below is a list of what I've tried so far.

1. Replaced solenoid valve and determined that the original and new valve were opening and the passage was completely free.
2. Replaced Facet pump with identical new pump and confirmed that both would function well with short inlet hose.
3. Confirmed that the plumbing from the pump to the on-board fuel tank is completely open.
4. Pressurized aux fuel line and looked for bubbles with soapy water to find any leaks. Found no leaks.
5. Removed and re-installed / re-sealed all fittings on inlet side of aux fuel line and on-board connections, filled lines as best I could with diesel, applied air pressure to end of dip tube and and looked for leaks. Found none
6. Removed and inspected filter screens on both pumps and looked for trash / sediment. New pump was spotless and old pump was very clean.
7. Measured voltage powering aux fuel pump with generator running, looking for low voltage / voltage drop. Pump was pumping diesel with short inlet tube so that the pump was actually under load. Test repeated for both old and new pumps. - No problem found.
8. Measured voltage powering aux fuel pump with direct connection to batteries bypassing on-board wiring. Pump was pumping diesel with short inlet tube so that the pump was actually under load. Test repeated for both old and new pumps. No discernible voltage drop when either pump was running.

 

[Guyfang]

This is something simple. I have been thinking for two days about this problem. I have used this same gen set, on Aux fuel setting, with two 25 foot hoses, and never had a problem with fuel. It would seem to me, that the problem has to be on the suction side, as there is no leak someplace on the pressure side. And if there was a problem on the pressure side, the leak would be noticeable. That leaves only the hose, the fuel adapter/pickup on the aux tank. But you have pressure tested the hose. Strange, strange. This is got to be something simple.

 

[glcaines]

This is something simple. I have been thinking for two days about this problem. I have used this same gen set, on Aux fuel setting, with two 25 foot hoses, and never had a problem with fuel. It would seem to me, that the problem has to be on the suction side, as there is no leak someplace on the pressure side. And if there was a problem on the pressure side, the leak would be noticeable. That leaves only the hose, the fuel adapter/pickup on the aux tank. But you have pressure tested the hose. Strange, strange. This is got to be something simple.

I absolutely agree with you. It has to be on the suction side. Perhaps there are multiple pinholes in the hose that are small enough that I didn't see any bubbles with the soapy water when I pressurized with air but between all of them enough air gets in to kill the suction of diesel fuel. Or perhaps the holes only open up in the hose when there is suction and not pressure? I intend to find out the cause. I'll post the cure once I find it.

 

[Bmxenbrett]

I would try replacing the suction hose. Or add a section of clear hose directly to the suction side of the pump.

 

[pjwest03]

I would probably try plugging both ends, having a schrader valve on one end. Then pressurize it and submerge the whole thing.

 

[Guyfang]

The way I used to test hoses, (and tubing) was to hook them up to a pressure source and submerge them in water. The 25 foot hose is a fine thing, and tough as can be. But when exposed to sunlight for decades, developed leeks. The steel mesh in them tends to rust also. For a while, in the 70's, we could not get short hoses for the 60 KW's. the book had them coded, (and still does) as manufacture by unit. I could not get hose, so I found an aviation unit NCO with a hunger for Huppendorfer beer. I had nice aircraft grade lines, that never need to be looked at again!! I know the steel braided lines are expensive, but if you buy an old set, and feel like the hoses are questionable, steel braided lines will be a one time buy. They never go bad.

 

[glcaines]

The way I used to test hoses, (and tubing) was to hook them up to a pressure source and submerge them in water. The 25 foot hose is a fine thing, and tough as can be. But when exposed to sunlight for decades, developed leeks. The steel mesh in them tends to rust also. For a while, in the 70's, we could not get short hoses for the 60 KW's. the book had them coded, (and still does) as manufacture by unit. I could not get hose, so I found an aviation unit NCO with a hunger for Huppendorfer beer. I had nice aircraft grade lines, that never need to be looked at again!! I know the steel braided lines are expensive, but if you buy an old set, and feel like the hoses are questionable, steel braided lines will be a one time buy. They never go bad.

I pressurized the hose to 25 PSI and used soapy water out of a spray bottle. I'll take your suggestion and repeat the test and submerge the aux fuel hose in water. This is very easy to do.

 

[uniquify]

Another random thought from way out in left field... when you were running the aux pump with the full length hose and draw tube, is there any chance the draw tube was vertical and suction sealing itself tight against the bottom of the barrel/bucket/container?

 

[glcaines]

Another random thought from way out in left field... when you were running the aux pump with the full length hose and draw tube, is there any chance the draw tube was vertical and suction sealing itself tight against the bottom of the barrel/bucket/container?

That was a good thought, but no, that wasn't the case.

 

[Farmitall]

Another random thought from way out in left field... when you were running the aux pump with the full length hose and draw tube, is there any chance the draw tube was vertical and suction sealing itself tight against the bottom of the barrel/bucket/container?

I don't think the pick up tubes go all the way to the bottom of a 55gal drum. That would not be a good thing as it would pick up any water/sediment.
In a 5gal can, it goes in at an angle to the opposite corner of the container so sealing against the bottom is not possible.

 

[uniquify]

I don't think the pick up tubes go all the way to the bottom of a 55gal drum. That would not be a good thing as it would pick up any water/sediment.
In a 5gal can, it goes in at an angle to the opposite corner of the container so sealing against the bottom is not possible.

Agreed, that is the case when using a bung adapter, but I thought I'd read the the OP was connecting the hose direct to the draw tube. So in my mind, all bets were off.

This is turning out to be a tough puzzle to solve. I'll be very interested to see what the root cause is once once this is resolved.

 

[Light in the Dark]

Now I am not saying I have insider knowledge... but with Russia-phobia running at full tilt right now, it begs the question: was there any intervention?

 

[glcaines]

Now I am not saying I have insider knowledge... but with Russia-phobia running at full tilt right now, it begs the question: was there any intervention?

View attachment 723512

That might explain a lot!