Fuel vent

crbnunit · Post by **crbnunit** » Fri Feb 27, 2009 10:30 am

I thought about that after I posted but if we can't fill the tanks to the top, don't we effectively loose those gallons anyway? I thought about the tube routing as well and will check as soon as I get back into town.

Duane · Post by **Duane** » Fri Feb 27, 2009 11:35 am

One thought here, pushing the vent line up is a good idea, however, make sure it wont rub on the wing skin.

crbnunit · Post by **crbnunit** » Thu Mar 12, 2009 1:13 pm

OK, just to add fuel to the fire... Hopefully not!!! I looked in the Maule maint. nanual at the tank installation/removal section. The vent line on the exploded view has a note attached to it; "In aircraft without vented caps". The same exploded picture has periscope caps shown. I interpret this to mean you do not need vented caps if you have vent lines installed.

I have been out of the state so I have not had the time to work on this problem but I went out yesterday and pulled the temporary plug on the vent. It started leaking immediately in a 1/4" stream. I attached a hose to the vent line and blew air to clear the line of fuel and break the siphon. It leaked faster... Didn't occur to me until later if it does not have vented caps, I just presurized the tank! I'll go back out, remove the caps and try again. This time I'll go prepared with a gas can and let it drain until it stops.

This is kind of bogus. If you can't fill your tanks all the way up, how do you know how much fuel you have onboard? Not like the fuel gauges are anywhere near accurate enough to make estimates.

I'm up for an annual. Any good Maule mechs in the Merrill field area?

aero101 · Post by **aero101** » Thu Mar 12, 2009 6:09 pm

Be careful putting pressurized air into the vent system, easy to blow a seam in the tank.... I would suggest fill your tank, attach a hose to vent into a gas can and measure how much you actually lose before it stops. Probably not nearly as much as you think unless your fuel tank dented or otherwise collapsed in area of the vent fitting at tank? Might be worth popping off the tank cover and taking a look?

crbnunit · Post by **crbnunit** » Thu Mar 12, 2009 6:30 pm

No worries. I don't think my lungs can generate that kind of pressure!

No way I would use compressed air. I saw a buddy blow up a motorcycle tank trying to get a dent out. Would have been funny had it not been a very rare bike.

It has probably drained for a good 3-4 minutes so far. I'll see how much longer it drains and measure. It HAS to be getting close!!!

crbnunit · Post by **crbnunit** » Mon Mar 16, 2009 10:35 am

Well, I finally got back over to work on it this weekend. As much as I hate to admit it, you guys were right. I put a hose on it and let it drain into a can. It took 5min. 10 sec to finnish draining and only put about 1/2 gallon into the can. The rate was much slower than I thought. Im guessing I lost about 2gal total. Not nice, but better than I thought.

Thanks for all the replies and advice.

Post by **andy** » Mon Mar 16, 2009 11:20 am

I fill my MX-7-180 tanks to about 1" below the filler necks to avoid siphoning. Way back in time I measured roughly how much less fuel that represents by switching the fuel selector, filling up one tank and draining it down to approximately 1" below the viller neck. It's about 1 gallon less per tank. The aux tanks are smaller than the main tanks so it's not quite as much for them, but close enough. Now I use a value of 38 gallons of fuel for "full" main tanks and 28 gallons for "full" aux tanks.

Andy

Fuel vent

Who is online