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Thread: MEP-803a : AirTex fuel pump substitution

  1. #1
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    Default MEP-803a : AirTex fuel pump substitution

    My 803 had a Facet 40193 primary fuel pump installed in it. I was having problems with it dragging down and shutting off after brief periods of load testing. I could not find the recommended AirTex E1074 anywhere. Replacement Facet pumps were over $200, that didn't seem like a good choice given that they replaced it with an AirTex pump. I found that AirTex has a technical support line and they do answer their phones. They recommended an E8131, I got one on Amazon along with a small fuel filter element.

    I also ordered a fuel pressure gauge and used a t-fitting to put it in line with one of my injectors so I could see what was going on before and after the replacement.

    pressure setup.jpg

    Here's my original pump:

    pump before.jpg

    Here's the pressure with the pump running, but not the engine:

    pressure before.jpg

    I had about 3.5 psi with fuel flowing through the filters and back to the fuel tank through the return line. When I pinched the return line the dead head pressure was 5.5 psi. I tried running the engine to see what effect it had on the pressure and found that the injector pump action causes the needle to fluctuate from 0.5 psi to 3.5 psi. This is probably not good for the gauge, a damped one might be better, but seeing all the fluctuation was interesting, too. Seems like there's not much fuel pressure margin when the injector pump is running (low pressure close to zero), if things aren't working just right and there's a little more demand the injectors aren't getting what they need.

    I swapped out the Facet for the AirTex:

    pump after.jpg

    Repeated pressure testing:

    pressure after.jpg

    I had a bit less than 7 psi with fuel still flowing back to the fuel tank through the return line. When I pinched the return line the dead head pressure was 9 psi. I tried running the engine to see what effect it had on the pressure and found that the injector pump action causes the needle to fluctuate from 3.5 psi to 6.5 psi.

    The unit performed well under load testing. I gave it ten minutes at 50%, 85%, 95%, and 115% with no problems. I'm calling the replacement a tentative success, time will tell how it holds up.

    -- Carl

    P.S. One thing I learned from this effort: when there's a big hurricane headed your direction, no one complains about time spent working on your generator. Stay safe, guys!

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    Great post Carl!!

    Information and pictures. Nothing better.

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    I will bump this back to the top since the subject comes up in almost every troubleshooting thread we see.

    From all I've read it seems the Facet 40193 pump was unreliable and very expensive. The Airtex E1074 seen on most newer units is not available nor are the specs.

    I think the important thing to remember is the mechanical pump on the engine does the actual work. The supply pump just needs to maintain a steady supply of fuel to the mechanical pump.

    My Airtex E1074 delivers 15 GPH and has a dead head pressure of 6 PSI. A better reference would be the operating pressure teed into the system but I didn't do that. For future reference I would like to see several known good working systems tested. If I get time before someone else does I will try to figure what fittings are needed to tee into the system for testing. Carl may already know this since he did it so a share would be helpful there. If we all know what the operating pressure and volume on good working units are we can all eliminate the fuel delivery pump when troubleshooting a problem unit.

    What we know so far is Carl's unit ran okay with a pump delivering just under 7 PSI. My unit performs as it should with a pump that dead heads at 6 PSI so we can assume it makes less pressure in free flow in the system. My pump delivers 15 GPH which I believe to be the critical factor. The original Facet pump was rated to deliver 10 GPH and since it ran units okay when new I would assume that value to be adequate.

    At the end of the day it looks like ANY 24 volt pump that can do 6 PSI at 10-15 GPH should run these units fine.
    MEP-803A

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    Quote Originally Posted by csheath View Post
    If I get time before someone else does I will try to figure what fittings are needed to tee into the system for testing. Carl may already know this since he did it so a share would be helpful there.
    Search for "Anderson Metals Brass Hose Fitting, Tee, 1/4" x 1/4" x 1/4" Barb". I pulled the hose from one of the injectors and tied in there with some fuel line from the local generator parts... err... that is... auto parts place.

    My Mr. Gasket 1561 Fuel Pressure Gauge began leaking fuel after running 40 hours or so. Could be that it wasn't designed to get hammered constantly by the pressure variation from the injection pump. At any rate, suggest thinking of this as temporary instrumentation. You don't want to wake up to silence in the middle of the night because your leaking pressure gauge sprayed most of a tank of diesel around the inside of your generator. Been there, done that, wasn't fun...



    -- Carl
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    Quote Originally Posted by m32825 View Post
    My Mr. Gasket 1561 Fuel Pressure Gauge began leaking fuel after running 40 hours or so. Could be that it wasn't designed to get hammered constantly by the pressure variation from the injection pump. At any rate, suggest thinking of this as temporary instrumentation.
    So what you are saying is you took a standard gauge, let it fill with a fluid so it becomes one of those premium liquid filled gauges? See, I have problems with my gauges losing fluid, not gaining... We should trade.

    I do like the red tint though.

    I do apologize for not adding anything useful in this thread. I couldnt resist, going back to my cave.
    It's not that I have too many generators, it's that I don't have enough room.

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    4 Star General Light in the Dark's Avatar
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    Care to share the info on the small fuel filter that goes on these sets?
    Non Semper Erit Aestas

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    Quote Originally Posted by Light in the Dark View Post
    Care to share the info on the small fuel filter that goes on these sets?
    Airtex G-17 filter.

    -- Carl

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    4 Star General Light in the Dark's Avatar
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    Thank you Carl
    Non Semper Erit Aestas

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    Quote Originally Posted by Light in the Dark View Post
    Care to share the info on the small fuel filter that goes on these sets?
    MEP-8xx Fuel pump and small filter
    ~~Later Mike

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    Has anyone cut appart one of these small filters? I would assume it is just a strainer to keep large stuff out of the pump.

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