D

dspender

Well Known Member
Patron
I have an RV 10 and dual G3 X touch screens. I did the fuel calibration on both tanks last night and that went flawlessly. However when I drain the tanks the indication is that I still have 30 gallons in each tank even though both are empty. Each addition of fuel lowered the displayed input voltage giving a nice graph. However now with the tanks empty the screen indicates 30 gallons yet in each tank and the input voltage is lower then I saw at any point last evening. my fuel sender's gave appropriate ohms readings before I install them in the tank and both tapped the upper or lower portion of the tank when I inverted the tanks indicating the senders were moving appropriately. why would the indicated input voltage be reading lower than the lowest reading I received last evening at the 30 gallon mark. Obviously that is why the screen is indicating full tanks even though they're empty.
 
Sounds too familiar. The RV-9A gauges are wonderfully accurate when they are. And when they aren't, they're awful. I've made friends with the fuel totalizer page... (it's the tab at the top right of the engine display page).

Ed
 
I changed sending units (using the ceiscorp.net magnetic senders). One on the upper side of the dihedral, one in the stock Van's position (same setup both tanks). I receive indications through the entire fuel range (top senders send signal to lower, then lower senders work when fuel gets to their working level). No more "guessing" for the first couple hours of flight. Incredibly accurate - no false indications - no electronics in the tanks! All coupled to a G3x dual screen system.

I am glad to have changed from the stock sending units and will do it on my next a/c as well!
 
I have a god calibration curve. With each gallon added the indicated voltage dropped slightly as expected. On its own the voltage is now a little lower indicating I still have fuel in the tanks even though they are empty.
 
One thought I have had; the baseplate that screws into the inbd wing rib is not grounded to the airframe. The rubber gasket keeps it from the rib and I used washers with a built in gasket to assure no fuel would leak through the screw holes. I am wondering if I placed a grounding strap on the baseplate to frame or used a plain washer under at least one the attach screw if that would allow a ground to the baseplate and make a difference.
 
FYI all, the domain is ciescorp.net. The one Layne posted is typo'd. More importantly, Layne, which sender did you use? The universal magnetic one, or which one off their aircraft sender page? Looks like you really just to contact them in order to figure out what sender is applicable and how to buy. Interesting nonetheless.
 
Dennis, lack of a good ground is a common problem. I had one sender that misbehaved, and inserting a star head washer under a single mounting screw solved the problem. I used proseal to seal the sender, and understand that the rubber seals can give you problems down the road.

Andy
 
Scott - Scott from Cies set the system parts list up for me - we had to use a combination of what he makes to complete the install on the -10. I then had to do the fuel calcs (I used 2 gal increments), record them, then Scott mapped and flashed the senders electronics. Then I installed the newly flashed electronics cards back in the senders (all this can be done while tanks installed). I then had to again do the fuel calcs for the G3x set up. Scott now has the information to flash any other -10 and knows what parts are needed to complete an install - a great benefit to the next user!

I'm flying the 40 off, and am impressed with the systems accuracy - absolutely no fluctuation (of fuel qty.) and complete fuel count from full to empty. I highly recommend this fuel measurement system.
 
Grounding was the issue. Originally I used proseal. Then I realized with the first iteration of calibration I had built the sender wrong. I neglected to place the 90 degree bend at the sender in the float rod. I was getting now voltage variations with added fuel because the float and rod we just spinning in place. I needed to remove the tanks to get the sender unit off because of the stubborn proseal. Purchased new senders because I needed a new rod and decided to use the run gasket next time. Since I was using the rubber gaskets, my A and P suggested I use rubber gasket washers for the 5 screws so fuel would not leak through the screw holes. Second iteration of calibration gave me goofy results as well. Then I realized the base had no ground because of the rubber gasket around the washers. I removed one of those washers and installed a usual AN960-10 washer and now had a good ground on the base of the sender. Calibration worked. No voltage reading change after 24 or 26 gallons though as the float in the sender evidently can not elevate any further due to the dihedral of the wing. However when the G3X indicates 0 gals, only 1/4 to 3/4 of a gallon remains in either tank.
 
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