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Fuel leak at cabin-fire wall fitting.

Dwillows

Member
Several posts mention very difficult access to fix leakage at the top of the flared aluminum fuel line where it connects to a tapered firewall fitting.

You can inspect the blue B nut and fuel line tubing on that fitting for leakage without removing anything and no awkward gymnastics.

Get a USB Endosope ($19.99, Amazon). It is idiot-proof, I checked it. Tape the camera cable to a ~16”long, ~1/8” dia rod with 2-4” of flexible cable extending the camera cable beyond the rod-end so you can fine tune a bend there later.
Standing alongside the plane, slide the scope/rod/camera thru the existing hole in the panel F-01217-L. Move the camera end forward, upward and to the right blindly until you see the fitting at the top of that fuel line on your phone screen.

Turn on a fuel pump. If there is a leak, you will see it, trust me. If you want to fix it, you can turn the B nut 1-2 flats at a time. Here’s one way to access it.

Get a 11/16 “ crow’s foot (if needed, reduce its girth with a grinder), and a Coobeast Offset Extention wrench (about $29 Amazon).

To make space for the crow’s foot wrench access, remove the F-01244-L and R tunnel side covers to slide the extension wrench forward, under and then up onto the B nut. This last step is athletic but the endoscope helps.

To make space for the extension wrench access you can also remove the two AN3-21A center rudder pedal block bolts and drop down the bottom half block supporting the rudder/brake assembly… Just the 2 bolts, washers and the lower 1/2 block, NOT the whole assembly. The Coobeast with a 3/8” socket helps here too.

You can then tighten the B nut as needed and check for leaks.
 
Several posts mention very difficult access to fix leakage at the top of the flared aluminum fuel line where it connects to a tapered firewall fitting.

You can inspect the blue B nut and fuel line tubing on that fitting for leakage without removing anything and no awkward gymnastics.

Get a USB Endosope ($19.99, Amazon). It is idiot-proof, I checked it. Tape the camera cable to a ~16”long, ~1/8” dia rod with 2-4” of flexible cable extending the camera cable beyond the rod-end so you can fine tune a bend there later.
Standing alongside the plane, slide the scope/rod/camera thru the existing hole in the panel F-01217-L. Move the camera end forward, upward and to the right blindly until you see the fitting at the top of that fuel line on your phone screen.

Turn on a fuel pump. If there is a leak, you will see it, trust me. If you want to fix it, you can turn the B nut 1-2 flats at a time. Here’s one way to access it.

Get a 11/16 “ crow’s foot (if needed, reduce its girth with a grinder), and a Coobeast Offset Extention wrench (about $29 Amazon).

To make space for the crow’s foot wrench access, remove the F-01244-L and R tunnel side covers to slide the extension wrench forward, under and then up onto the B nut. This last step is athletic but the endoscope helps.

To make space for the extension wrench access you can also remove the two AN3-21A center rudder pedal block bolts and drop down the bottom half block supporting the rudder/brake assembly… Just the 2 bolts, washers and the lower 1/2 block, NOT the whole assembly. The Coobeast with a 3/8” socket helps here too.

You can then tighten the B nut as needed and check for leaks.
Thanks for sharing, I just placed my order for a coobeast extension.
 
Thanks for sharing, I just placed my order for a coobeast extension.
If you need to tighten the B nut, slip a wrench onto the tapered fitting in the engine compartment and wedge/hold it so the fitting cannot turn. Access here too is limited, so you might need to attach temporarily a curved extension onto the wrench handle to maneuver then wedge it in place.
Good luck!
 
If you need to tighten the B nut, slip a wrench onto the tapered fitting in the engine compartment and wedge/hold it so the fitting cannot turn. Access here too is limited, so you might need to attach temporarily a curved extension onto the wrench handle to maneuver then wedge it in place.
Good luck!
Luckily I don't have a leak and I just like new cool tools.
 
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