fuel transfer pump

cj8vet · Post by **cj8vet** » Mon Aug 06, 2007 6:18 am

My left pump has begun making a loud noise when operating. Is it dead?dieing? where is it and how big a deal is it to change?/rebuild?
thanks
mark
mxt180

mikemike · Post by **mikemike** » Mon Aug 06, 2007 8:02 am

Mark, I'm guessing that you are hearing it with the engine off. They make a pretty good racket. Check to see that it is secure. If its tied down, I wouldn't worry about it. If you can hear it with the engine running, something is wrong. Maybe others have had a difference experience. YMMV. It is located out on the wing where there is about a two inch diameter hole in the lower wing. With the pump running, you can go out under the wing and identify the location by sound and feeling where the greatest vibration is coming from. IIRC the pump has a hexagonal piece barely extending below the wing. - Mike

a64pilot · Post by **a64pilot** » Mon Aug 06, 2007 9:43 am

They rattle like heck when they suck air, like when the tank is empty. It could be dead or maybe just sucking air from a loose line or something. Is it transfering fuel?

Green Hornet · Post by **Green Hornet** » Mon Aug 06, 2007 1:54 pm

I can confirm that mine make a quite a racket when the engine is off. Although with engine running and with ENC head gearI have to make sure to check gauges in order not to over fill.

maules.com · Post by **maules.com** » Sat Aug 11, 2007 5:28 am

Loud rattle noise when not getting fuel. Loud thumping noise when pumping fuel. Engine off. Cannot be heard with engine on.

W.A.T. · Post by **W.A.T.** » Tue Aug 14, 2007 9:02 pm

For what it’s worth…I have had many Maule’s come in for Annual with transfer pumps rusted on the inside from lack of cleaning and water collecting from condensation. It works just like the gascolator on the firewall. It has a screen that must be cleaned at each Annual. Not every mechanic seems to know this. Recommend checking yours just to see. It is very easy; you only need one tool to access it. Older pumps will require a 5/8 box end wrench newer pumps require a 7/8 box end wrench. Recommend having the tip tank empty, but not required. A bucket will be required to catch a small amount of fuel. Have a friend hold the bucket under the fuel pump while you loosen the large nut on the bottom of the pump (1/4 turn only). If he is not a good friend maybe let him loosen the nut as fuel will tend to fun down your elbow. If the tank is full, fuel will continue to slowly run out until you replace the nut, (bottom of the pump). After the nut has been loosened ¼ turn remove the bottom of the pump, there is a screen inside, clean it with low pressure compressed air. You will find a magnet and gasket inside the bottom of the nut that was just removed, clean those parts as well. Inspect inside the pump body and nut for rust. If rust is found I recommend pump replacement. If no rust is present lubricate the gasket with engine oil and reinstall. Always test the pumps before starting the engine at each preflight. Do not run the pumps dry for more that a second or two.

Hope someone finds this helpful…checks can be made out to the address below.

mikemike · Post by **mikemike** » Wed Aug 15, 2007 3:48 am

Appreciate your insight, David.

cj8vet · Post by **cj8vet** » Thu Aug 16, 2007 6:06 am

Thanks for the replies guys, I just ordered a new pump from maule-150$
They said they last about 10yrs and sell 4-5 /month-it is a stock pump they get in and modify.???somehow
mark

a64pilot · Post by **a64pilot** » Thu Aug 16, 2007 8:43 am

cj8vet wrote:Thanks for the replies guys, I just ordered a new pump from maule-150$
They said they last about 10yrs and sell 4-5 /month-it is a stock pump they get in and modify.???somehow
mark

They probably modify it with a PMA stamp

210TC · Post by **210TC** » Thu Aug 16, 2007 11:07 am

LOL...................

akloon · Post by **akloon** » Sun Aug 19, 2007 11:31 pm

Don't let them run dry for more than a second or two? How the hell can you tell if they're really dry with the stock fuel gauges we've got? Mine have probably run for 10 minutes dry when I'm trying to get all the gas out of them!

yellowbelly · Post by **yellowbelly** » Mon Aug 20, 2007 2:01 am

Guilty as charged...
I like to land with as much of my fuel moved to the mains as possible. Once (OK, maybe MORE than once) I found myself taxiing in wondering what the heck all that racket was. This always happend after I got distracted during the approach and landing. Now I stick a yellow Note It in the middle of the panel any time I turn the transfer pumps on.

BTW: someone at the factory told my they can run wet or dry. Was I lied to? IIRC, his last name was Maule...

a64pilot · Post by **a64pilot** » Mon Aug 20, 2007 5:33 am

Oh, I'm sure they will run dry. I think it may shorten their life to do so. I run them until the gauge reds E. On mine that leaves a couple of gallons in each tank. For some reason my right one pumps a lot faster than the left one.
Very similar transfer pump system on a Beechcraft has the pump pumping through a restricted orifice. There is a pressure switch between the pump and the orifice. When the switch is thrown the pump runs on a timer for X number of seconds, in order for the pump relay to remain latched the pressure switch must be closed. There must be pressure to close the switch of course so the pump runs until fuel is exhausted, pressure drops, switch opens and pump relay opens removing power to the pump even though the switch is on.
If it does not hurt the pump to run dry, then someone sure went to a lot of trouble for nothing.

210TC · Post by **210TC** » Mon Aug 20, 2007 7:05 am

Guilty also,
Mine are 26 years old (no log book entries show replacement) and I have run them dry a zillion times and they keep on tickin.
We have had this same pump on equipment owned in the past at our farms. Sometimes the operators would leave the fuel caps off after refueling and dirt the trash along with a little rust would clog the pumps to the point the engine would stop. I recall having to dig out the round filter, after cleaning and reinstalling the filter presto we got back to work. GREAT pump. I prefer it over any other pump.

Green Hornet · Post by **Green Hornet** » Mon Aug 20, 2007 9:11 am

I had mine looked at this annual and the filters needed some cleaning otherwise looked good.

fuel transfer pump

fuel transfer pump

Pump Noise

Fuel Transfer Pump

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