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RV-14 QB Blocked Fuel Tank Vent

M

Meat

Active Member
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Hello All,

Has anyone encountered a blocked fuel vent line in a QB tank? I was going through Section 18 on my tanks ensuring all work was done to plans and completing any unfinished items. Page 18-06 says to "double check that the vent line is clear and has not become blocked with sealant." The left tank was fine. I could easily blow through the external fitting. The right tank seems to be completely blocked. I can neither blow nor suck any air through the fitting. Now what? A possible solution to me is blowing compressed air through the fitting in an attempt to remove the blockage which I assume is tank sealant. Not sure that would even work since cured sealant is pretty sticky, tough stuff. But in keeping with the "First, Do No Harm" mantra, I wanted to see if anyone else had any thoughts or has encountered this issue. Frustrated this wasn't caught by Van's first.

I appreciate everyone's time.
 
Faulty AN832 fitting

Further investigation revealed the blockage is not due to Pro Seal. Rather the external blue AN832-4D fitting was not drilled through. A #30 drill bit inserted in the fitting end stops approximately 1" inside. I can view through the end and see blue metal when it should be a clear pass through. The other tank fitting is fine. Clearly a faulty fitting. Grrrr...... I'm pondering now whether I can carefully drill a hole through it without removing the entire fitting and disturbing the Pro Seal there. Maybe use a drill bushing inserted inside the fitting hole with a drill bit inside that.
Thoughts?

Cheers,

Scott
 
Before you do anything else I would really recommend using a borescope or remote camera through the fuel cap fitting to inspect the bulkhead fitting from inside the tank. The chance of a defective fitting is low. What you may be seeing is a cap on the inside of the tank. In other words the vent line was not attached to the fitting at final tank assembly and a shipping cap was left on instead.

Looking at the drawing now I see it would probably be easier to insert the camera through the fuel line fitting. It should be large enough to insert a small diameter camera. Remove the VA-261 filter fitting first.
 
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Thanks for the reply. I can easily view the vent line through the fuel tank filler opening using a light and mirror. The vent line is definitely attached to the external AN832 fitting. The blockage occurs 1.03 inches from the external long end of the fitting. So well inside either end of the fitting. I don't think it's a cap. The blockage appears to be the same blue aluminum color and it feels metallic when tapped. What I don't know is how thick the blockage is. A manufacturing defect and it wasn't drilled all the way through originally? I'm pondering if I can carefully drill through it. A #30 drill bit fits well in the end. Maybe use a drill bushing inside the hole. Just need to keep the drill square and proceed slowly. Replacing the fitting looks nearly impossible with the limited access. And it's already been prosealed into place.

Cheers,
Scott
 
Meat said:
Thanks for the reply. I can easily view the vent line through the fuel tank filler opening using a light and mirror. The vent line is definitely attached to the external AN832 fitting. The blockage occurs 1.03 inches from the external long end of the fitting. So well inside either end of the fitting. I don't think it's a cap. The blockage appears to be the same blue aluminum color and it feels metallic when tapped. What I don't know is how thick the blockage is. A manufacturing defect and it wasn't drilled all the way through originally? I'm pondering if I can carefully drill through it. A #30 drill bit fits well in the end. Maybe use a drill bushing inside the hole. Just need to keep the drill square and proceed slowly. Replacing the fitting looks nearly impossible with the limited access. And it's already been prosealed into place.

Cheers,
Scott
Click to expand...
If it is a defective fitting, which it looks to be that way, it seems the only option is to drill thru it. The only realistic way to deal with this is to open the back baffle to gain access which would be the last resort. Of course you can always ask VANS and see f they will replace the tank but then you may have to wait for some time to get things back.
 
Thanks very much for forwarding me that info. I ended up drilling out the blockage using a 5/32 OD brass tube as a drill bushing and a #31 bit inside the bushing. Then I upsized the opening to #21. The thickness of the material causing the blockage was about .150. Then I carefully cleaned out any chips. Everything seems good now so building on....

I appreciate everyone's response.

Regards,
Scott
 
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