Scott Hersha
Well Known Member
For those with QB wings and therefore finished fuel tanks, here?s something to check before installing the fuel level sender and large inspection plate opening on the inboard tank rib with pro seal. The B-nut on the inboard end of the tank vent line may not be tight. It?s easy enough to check and exercising due diligence, it should be checked - just like the proper bolt torque on all the Z-bracket bolts. I?ve found these loose, but for some reason I didn?t think to check that B-nut. If you have fuel dripping out of your vent line when the tank if fairly full but the outboard end of the vent line is ?above water?, then your B-nut is probably loose. It shows up when the air in the fuel tank heats up, has no where to go and forces fuel up and over the loop in the vent line. We?ve had 4 of these at our airport all on QB RV wings. I had the joy of removing the tank and then the inspection plate on my right tank to gain access. The nut was barely finger tight. This won?t show up on a tank leak test because the vent bulkhead fitting is capped off on the outside.
Here?s another thing to consider when doing this part of your project. You might want to run a dedicated ground wire to one of the fuel sender mounting screws if you?re pro sealing these in place. My left fuel level sender had an intermittent indication, going from correct reading to empty intermittently, with warnings from the G3X about an empty fuel tank. I removed one of the mounting screws on the sender, cleaned off the pro seal, installed a wire with a ring terminal and a lock washer under the screw and then re-prosealed it. The lock washer insures a good ground connection. This ground wire is grounded under one of the inboard Z-bracket bolts. This is easy to do without removing the tank. I put one on the right tank also, just to be sure, since I had the tank off anyway. Seems I had enough proseal under the sender mounting screws and/or the inspection plate mounting screws to disrupt a smooth pathway to ground. That fixed my indication problem.
Here?s another thing to consider when doing this part of your project. You might want to run a dedicated ground wire to one of the fuel sender mounting screws if you?re pro sealing these in place. My left fuel level sender had an intermittent indication, going from correct reading to empty intermittently, with warnings from the G3X about an empty fuel tank. I removed one of the mounting screws on the sender, cleaned off the pro seal, installed a wire with a ring terminal and a lock washer under the screw and then re-prosealed it. The lock washer insures a good ground connection. This ground wire is grounded under one of the inboard Z-bracket bolts. This is easy to do without removing the tank. I put one on the right tank also, just to be sure, since I had the tank off anyway. Seems I had enough proseal under the sender mounting screws and/or the inspection plate mounting screws to disrupt a smooth pathway to ground. That fixed my indication problem.