Update to the much discussed Fuel Sender installation/sealing.
Van's provides the Float Wire Bending Diagram that gives you most of the information you need. Note the various dimensions for different aircraft:
https://drive.google.com/file/d/1teW...ew?usp=sharing
Senders: Stewart Warner F-385B (Left) and the F-385C (Right). I found that the cheapest and easiest place to get these is Summit Racing ($35 in 2020). If you have a retail store nearby, they are probably in stock. Currently, they are being supplied with a black rubberish gasket. 240 - 32 Ohms.
Gasket: DISCARD!! The Van's document says to discard and use sealant. I just replaced my 11 year old senders, and I was shocked to find the builder only used the rubber gasket. It was not leaking, but the gasket fell apart as I removed the sender. It was cracked throughout. Just a matter of time before I had big problems. The only good part is the gasket came off easily and prep for the proseal was a piece of cake (no sealant to clean up!).
https://drive.google.com/file/d/1JnY...ew?usp=sharing
The paint on the gasket is only a few months old, and not a cause for the cracking.
90 Degree Bend: This diagram clearly illustrates the dreaded 90degree bend that locks the float into place. Some will proseal the wire into the sending unit. I would not recommend this practice as the proseal will easily flake off the nylon sender, and provided little retention. If this is a concern, use a small amount of epoxy, but do not to allow it to interfere with float movement.
Float orientation: The floats easily pop in and out of the wire. Van's diagram is a bit confusing. On my RV6 I had to reverse the orientation of the RIGHT float as it made contact with the stiffener in the tank. So the RIGHT float has the long part to the AFT. The LEFT float has the long part FWD.
Float security: I used safety wire to secure the floats into the wire. This also put a bit more tension on the float to prevent them from rattling around.
https://drive.google.com/file/d/1lEb...ew?usp=sharing
Screws: I replaced the #8 pan head phillips screws with #8 X 3/4" socket pan heads. This allowed removal and install to be much easier.
Remove Tank?: Removing the tank makes the fuel sender part of the job, easier. You can more easily check range of motion of the sensor (turning the tank upside down and listening for contact with the skin), and less mess with the sealant. However, keeping the tank on, and replacing the senders at the wing root is not too big of a deal. Remove the fairing, and approach the sensor from underneath as you have more room with which to work.
Sender grounding: I haven't heard this discussed, but the resistance used is measured from the electrical post, through the variable resistor, and them to ground on the mounting plate. As so much sealant is used on the plate and the screws, I decided to improve the ground. After protecting the nylon pieces of the sender with an aluminum heat shield, I soldered a wire to the outside face of the mounting flange. I will take this to a good aircraft grounding point.
I hope this thread consolidates some of the Fuel sender information spread throughout the forums.
Fly Safe,
Jimmy
Stewart Warner Fuel Senders/Replacement/Sealing
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