Fuel Sender Ground

[cajunwings]

In the home stretch of my 9 rebuild. Opened up the fuel tanks to have a look around and found this unusual configuration for the sender ground. Never mind the nutplates are on the outside of the rib and the sender was mounted on the inside ?? But the builder went to some trouble to run the ground wire through the cover plate. It’s insulated from the cover plate as well by the block of UHMW which seems redundant if it was probably going to be grounded somewhere anyway. Maybe the plan was to run the ground all the way back to the gauge? Anybody ever see anything like this or wire their senders this way. Mystified in La. Fabbed up a new cover plate per the plans and soldered the wire back on the sender where it belongs and with a meter it seems to be working normally.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

 

[clarenceoveur]

In the home stretch of my 9 rebuild. Opened up the fuel tanks to have a look around and found this unusual configuration for the sender ground. Never mind the nutplates are on the outside of the rib and the sender was mounted on the inside ?? But the builder went to some trouble to run the ground wire through the cover plate. It’s insulated from the cover plate as well by the block of UHMW which seems redundant if it was probably going to be grounded somewhere anyway. Maybe the plan was to run the ground all the way back to the gauge? Anybody ever see anything like this or wire their senders this way. Mystified in La. Fabbed up a new cover plate per the plans and soldered the wire back on the sender where it belongs and with a meter it seems to be working normally.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

Wow, thats crazy!

 

[Richard Connell]

It’s possible that the original builder may have planned for a second outboard sender in series with the inboard sender in order to measure the fuel the inboard sender alone misses.
This is how you would achieve that.

 

[airguy]

No reason to have that, unless as pointed out above, there was a plan for two senders in series.

The single sender in the root cannot sense any fuel in the tanks above about 3/4 full - because the float is at the maximum extension at that point and can't go any further. The solution is to put another sender in the farthest bay and wire them in series - which means the ground of one sender is attached to the power input of the other. Then both floats are moving in response to fuel and you can more accurately gauge the total amount, from empty to full.

I did this on my RV10 wings, but I ran that wire inside the fuel bays rather than take it externally. Any wire penetration through the tank runs the risk of eventually having fuel seep out through the miniscule gaps between the wire strands themselves, unless steps are taken to seal the ends of the wire with proseal.