How important are the extra fuel pumps? MEP003a

[North Maine]

I've been slowly getting my new-to-me MEP003a working and i just finally tracked down a "fish-biting" issue I thought was plugged fuel filters but was actually a dead fuel lift pump. At some point in the machines past the aux-transfer pump disappeared so my unit had only two fuel pumps, and they were plumbed inline feeding the filters. The downstream lift pump is/was dead and I guess they don't "flow-thru" very well because I could barely fill the filters while priming after changing the filters out. Once I plumbed the system to one single lift pump pulling from the tank and discharging to the filters I got good fast flow and about 10PSI fuel pressure to the Injector Pump... no more fish biting. Now to the title question:

Is it important to have 2 fuel pumps inline? Is there a pressure requirement for the Injector pump not met by a single pump?

On a side note I have the hose and bung adapter for an aux tank... but now I guess I need to get a transfer pump to operate "as-designed" for an aux tank.

 

[Light in the Dark]

You only need 1 primary pump for it to work... two are there for survive-ability/redundancy in theater.

 

[cuad4u]

If someone installed the wrong Facet fuel pump, the two pumps in series will not work. The proper Facet fuel pumps will "pump through" even is one of the two pumps fails.

 

[Guyfang]

Sadly, because the pumps all have FACET printed on the front, people think they are all the same.

 

[Philratcliffe]

I’ve run my 002s for years on a single pump and then raised my 55 gallon fuel pump high enough to gravity feed the injector pump.

 

[North Maine]

Thanks guys. I couldn't imaging that the original design was not flow-thru- it defeated the point of it being redundant! My set has seen a fair amount of tinkering I'm afraid, so I'm not surprised to find out it has a non-original fuel pump.

 

[Buttweet]

Didn't realize the 3 pumps on mep003a were not all the same P/n. Can these pumps be disassembled, cleaned and be expected to work again. I'm not hearing the fast clicking and it will not start. Thx for any info on these pumps.

 

[Ray70]

The pumps are very simple to open up, clean and reassemble.
All that's in there are 2 check balls, top and bottom and a magnetic plunger that vibrates back and forth to move the fuel.
Most likely yours are just stuck from gum buildup.
Take off the base with a 5/8" wrench, remove the strainer basket and you will see a wire clip that is holding everything together.
Take it apart and clean everything and reassemble.

 

[Guyfang]

Didn't realize the 3 pumps on mep003a were not all the same P/n. Can these pumps be disassembled, cleaned and be expected to work again. I'm not hearing the fast clicking and it will not start. Thx for any info on these pumps.

I beg to differ. All three electric ful pumps are the same. There has of course, been a number of pumps bought by the milatary over the years, and some do have different part #'s, but they are all compatible. Also, there are a number of pumps that LOOK just like the "Right" pump, but are not. The main difference is that all the "Right" pumps must be able to let fuel flow through them, if they fail. That's why there are two pumps for fuel delivery to the IP. If one fails, the set is supposed to continue to run. Also the addition of the RFI filter on the newer pumps.

If you open TM 9-6115-584-24P, to PDF reader page # 72 and 74 states that all three pumps are the same. The attachment is an exploded picture that shows the pump parts that Ray told you of. This picture came from another TM. Rarely did anyone in the Army ever take one apart and clean it. It was easier to just order another.

 

[NY Tom]

One of my pumps died and for whatever reason the second one could not pull thru it. Pulled it apart and cleaned it. Moves easily back and forth inside. Put it in doesn't click.

Thoughts? It has power since by swapping the wires the good one still works. Could it be electrical in between whatever that round tube thing is?

Not finding in the TM anything on fixing the pump so far. Can you pull the wire off where it enters the pump? Seems awfully tight on there.

Anyone have a pump they want to get rid of? Reasonable place to find one?

 

[Chainbreaker]

One of my pumps died and for whatever reason the second one could not pull thru it. Pulled it apart and cleaned it. Moves easily back and forth inside. Put it in doesn't click.

Thoughts? It has power since by swapping the wires the good one still works. Could it be electrical in between whatever that round tube thing is?

Not finding in the TM anything on fixing the pump so far. Can you pull the wire off where it enters the pump? Seems awfully tight on there.

Anyone have a pump they want to get rid of? Reasonable place to find one?

A common issue is failure of the inline RF Filter making the pump inoperable. They are inline with the pump and are a round, or square, thingy depending on pump vintage...round were later superseded by square form factor. Just cut it out and butt splice the 24V wire back together.

Unless you have sensitive 2 way radio gear nearby (think Military) there is no need for the RF filters for civilian use, unless perhaps your a Ham Radio operator.

EDIT: Also the correct flow-through pump is Facet P/N 480517E (P/N is stamped on mtg flange). All 3 pumps should be that number for interchangeability.
If you don't use an Aux fuel source hookup you can think of the Aux pump as a spare pump and thus it should be the same model for redundancy/flow through.

 

[Light in the Dark]

Sorry to hear you are having issues with the pumps. The RF/EMI filters can definitely be a PITA. Cut them out, and get the cannon plug wired back up to the raw wire and see if they go (make sure you put back together in the most water tight way you are capable). I got in an 002 years ago fresh out of reset, and all 3 pumps were DOA (but looked brand new). Never can tell.

 

[NY Tom]

Thanks guys.
12V Facet flow thru pumps are available for under $100. P/N FAC-480534
Has anyone tried a 24v to 12v dc converter to step down the fuel pump circuits?
Seems in my head that this could be done fairly easily without changing actual OEM wiring. 20A converter IP68 rated for $18 on Amazon.

Two pumps and converter for less than one new original pump...

 

[Light in the Dark]

Dont spend a penny until you cut the EMI filters out.

 

[NY Tom]

Yes will do that of course thanks.

 

[glcaines]

Thanks guys.
12V Facet flow thru pumps are available for under $100. P/N FAC-480534
Has anyone tried a 24v to 12v dc converter to step down the fuel pump circuits?
Seems in my head that this could be done fairly easily without changing actual OEM wiring. 20A converter IP68 rated for $18 on Amazon.

Two pumps and converter for less than one new original pump...

I would keep it simple and use the 24 VDC pump.

 

[Chainbreaker]

I would keep it simple and use the 24 VDC pump.

I would tend to agree. If one were to introduce a 24 VDC to 12 VDC converter on the platform, that could introduce another potential failure point. When power is out and your running off genset, reliability is paramount.

 

[Guyfang]

If it works, don't fool with it. KISS.

 

[NY Tom]

Looks like the wire to the pump was damaged close to the pump. Got that little cap off. Going to solder on a new wire and it should be ok. Tested and the pump does run.

 

[Light in the Dark]

Even though they are expensive and the problem has been addressed and fixed, it might behoove you to put up (1) of the proper OEM pumps on your parts shelf for the future.