1965 337 Leaking Gas

Cpt_Kirk · #1 07-24-14, 10:36 PM

I noticed gas coming from an inspection panel underneath the right wing. We pulled the panel revealing the fuel selector. No fuel was leaking from the selector itself.

After troubleshooting a bit, we also noticed that the fuel vent for the Aux. Tank was completely clogged. We tried everything we could to clear it up to no avail.

My question is: Where could gas possibly come from in that area besides the Aux. tank, selector, and appropriate hosing? We can produce a leak on the ground, but can't find the origin.

Does anyone else have any experience with a situation like this?

hharney · #2 07-24-14, 10:58 PM

Could be coming from the tank itself. Maybe a seam or a small crack in the tank at a weld seam. I have seen this before and the fuel finds a path to follow so it may not be obvious where it is coming from. The fuel from the main tanks is routed from the tanks to the boom where there is a small sump then to the fuel selectors. The aux tanks are plumbed directly to the selector and bypass the sump in the boom. Which tank is leaking? Mains or Aux?

Mud daubers and bugs can clog the vents. This should be cleaned but can be a bugger (no pun

. Check the forum for other posts on this issue using the search feature. Also there is a procedure in the service manual on testing and checking the fuel vent system. There are some check valves involved.

You may have to pull the Structural panels on the upper wings to perform the repairs. If you do remove the panels be sure to follow the service manual guidelines to support the boom and the wing. Those panels are Structural to the wing.

Cpt_Kirk · #3 07-25-14, 12:18 PM

We believe it's the right Aux. tank and are beginning to believe it's the tank itself. We, unfortunately, bought it from a piss poor owner/A&P.

I'll take a look at the other threads when I get a chance. Thanks for the help so far.

hharney · #4 07-28-14, 08:48 AM

Not the end of the world to remove the inboard aux tank. The structural screws can be a little fussy to remove if they are all painted in and have not been out before. Take time with a good bit on a drill driver and make sure the paint is cleaned out of the screw head for best contact. I like to tighten the screw just a little first then start the removal. Be careful not to torque to much just enough to break it loose as it tightens then reverse the direction.

photos

http://www.337skymaster.com/messages...?t=2309&page=3It is if you have guys who aren't familiar with the Skymaster. Thanks for the pictures, they help out quite a bit.

I think this thing just needs another true annual.

Cpt_Kirk · #5 07-28-14, 09:10 PM

Quote:

Originally Posted by hharney

Not the end of the world to remove the inboard aux tank. The structural screws can be a little fussy to remove if they are all painted in and have not been out before. Take time with a good bit on a drill driver and make sure the paint is cleaned out of the screw head for best contact. I like to tighten the screw just a little first then start the removal. Be careful not to torque to much just enough to break it loose as it tightens then reverse the direction.

photos

http://www.337skymaster.com/messages...?t=2309&page=3

It is if you have guys who aren't familiar with the Skymaster. Thanks for the pictures, they help out quite a bit.

I think this thing just needs another true annual.

hharney · #6 07-29-14, 09:18 AM

Bring her up to Michigan for a clean inspection at Griswold Aviation. He specializes in Skymasters and owner assist annuals.