The Cessna 120-140 Association Forum

My engine has been running just a little bit off recently and after describing the operation to my IA he thinks I may have a little bit of water in my carburetor bowl. I see on the diagrams there is a drain plug held on by 25-30 in-lb of torque.

At first blush it would seem draining any water would be as simple as turning the fuel off, taking the plug off, letting it drain, then reinstalling the plug. With that, some questions:

Is it safe to do this with the air box and everything still attached?
Can I remove and install the plug by hand (the torque spec is barely finger tight)?
Do I need thread lube for the plug?
Is there any procedure to refill the bowl after I get done draining it before I start the engine next?

Not to say your A&P is not correct, but check this link. I was having poor idle and cutoff problems.......turned out the primer was leaking so allowing fuel to be sucked in thru the primer line.


https://msacarbs.com/carburetor-troubleshooting/

8451 wrote: ↑Tue Sep 03, 2019 1:13 pm Is it safe to do this with the air box and everything still attached?

Moderately. There isn't much gas in there, but then, it doesn't take much gas to start a fire, especially if it's all over your hands. Run the engine with the fuel valve (not the mixture) shut off to get as much out as possible, first.

Can I remove and install the plug by hand (the torque spec is barely finger tight)?

Everyone over estimates the strength of their fingers. Also, it usually takes more torque to break a fastener loose that it does to tighten it.

Do I need thread lube for the plug?

If it has a gasket, no. If it is a pipe plug, put some Fuel-lub (now E-Z-turn) on the threads.

Is there any procedure to refill the bowl after I get done draining it before I start the engine next?

It's a gravity feed system. Turn the fuel on and the bowl will refill. Keep an eye on it in case the float sticks.

It's a gravity feed system. Turn the fuel on and the bowl will refill. Keep an eye on it in case the float sticks.

What would the float sticking look like?

Gas pouring out of the carburetor or air box...