D

DJR

Active Member
I have the standard resistance type fuel level sensors in my tanks. Today, I put fuel in both of them for the first time and calibrated with the G3X.
The Left tank calibration went fine, but as I added fuel to the right tank, no change in resistance would occur until I tapped on the fuel sender access backing plate between the wing root and fuse(fairly firm tapping with a dead blow hammer).
Every time I added fuel (2 gallon increments), the resistance would not change until I did some more tapping. After tapping the resistance reading would stabilize and indicate closely to the same readings as the left tank. I had to do this at every 2 gallon increment until a full tank.
I really don't want to open that tank up, but i wanted to ask if anyone might have any ideas.
I put these senders in about 3 years ago. The sticky float assembly could be damaged or perhaps somehow proseal got n the wrong place, but seems strange how the tapping makes it move.
I am curious if anyone else has seen this.
Any thoughts would be appreciated.

Thanks
 
DJR,

I have a similar situation with my RV-8 left fuel tank sender. I had to rock the wings every few gallons to get the float to move in order to calibrate my tanks. Not an uncommon issue. Speculation is that that the leg of the fuel arm float is creating just enough friction on the sender unit to prevent it from freely moving.

Yes, it would be a PIA to fix, but if it doesn't free up I plan to remove and replace this summer. This can be accomplished without removing the tank.
 
I've been where you are (suspect fuel sender), and as much as I tried to rationalize it away, the bottom line was... we were going to have a brand new airplane with a bad fuel sender forever - until we bit the bullet , opened it up, and troubleshot the problem. In the end, it took about 3 hours, and that was on an RV-3 with much LESS access room than an -8....

(Of course, you can always hope that the vibration of the engine running might just negate the stiction, and it will operate fine.....or not....)

Paul
 
Ironflight said:
(Of course, you can always hope that the vibration of the engine running might just negate the stiction, and it will operate fine.....or not....)

Paul
Click to expand...
Perfect timing of this thread as I'm flight testing a friend's RV-8A and the right fuel sender is "sticky". Have to rock the wings to get the float to come down. After refilling the tank, it takes a minute or so for the level to indicate full. So it's clearly sticking UP and DOWN.
 
I had same problem

When my RV-8 was new and I was calibrating the sensors, I had the same problem. I spent the unpleasant hour taking the sender out, looking at it, fiddling with it, and putting it back.
I had suspected some wayward proseal, but no. The wiper in the reostat just seemed to be a bit more friction than normal. I tried adjusting the contact pressure of the wiper, oiled the pivot, tweked the float arm bends, a few other things. It seemed to work better, so I put it back in.
200 hrs later, it is still a little sticky, not like it was. But when flying I'll kick the rudder to make the fuel slosh to be sure I am getting a reliable reading.

Ultimately, the EMS fuel totalizer is so accurate that I only use the float gages for a backup sanity check. If there is ever a big discrepancy, I'll err on the cautious side and assume the lower reading until I can refuel. So it is not a huge deal to live with the sticky gage.
 
Same problem

I had an issue calibrating my right tank just last week. No change in level at all as I added fuel. As it turned out, I had a couple minor leaks, so I had to remove the tank to fix the sender and the leaks. The problem with the sender was the small rectangular "circuit card" that has the resistive segments on it had shifted off center. After re-centering the card, I glue it in place with CA glue (being careful not to get any on the resistive segments). Works great now. Leaks are fixed and the tank is ready to go back on. Hope to run the engine in a week or so, and have the A/W inspection soon afterward.
 
Ok, guess I'm not alone

Thanks for the replies. I am gong to fly it for a while and see if it improves, but will rely on "time flown" and the fuel flow readings as my primary fuel usage.
I appreciate the feed back.
 
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