Removing fuel sending unit

We sent our leaking fuel tank back to Van's to be repaired. They fixed the leak BUT now the fuel sending unit sticks. It will set at 30 gallons for days then suddenly drop to 12 gallons. It even sticks when filling the tank.

So we bought a new sending unit to replace it. BUT, Van's used fuel tank sealer to seal the sending unit and we cannot get it off. We called them and they said there is a solvent they sell to dissolve the sealer but we would have to remove the tank to use it??? We are not going to remove the tank. (at least not yet) They suggested we come up with some procedure to try to flex the unit and perhaps it would unstick. My feeling is mechanical devices rarely heal themselves.

So guys, you have come thru so many times in the past, you got a solution for this one?

Sealant

Yeah use the goop they sell the break down the sealant. Polygone. Be sure to tape off around the root rib and only get this stuff around the sender screws. Use a scrapper to get it there. The big danger is stripping the screws if you don't take the tank off. You should be able to get away with using new bits and firm direct pressure on the screws. Would also be beneficial to get anything out of your way such as fuel lines.

Bite the Bullet ...

JackinMichigan said:

We sent our leaking fuel tank back to Van's to be repaired. They fixed the leak BUT now the fuel sending unit sticks. It will set at 30 gallons for days then suddenly drop to 12 gallons. It even sticks when filling the tank.

So we bought a new sending unit to replace it. BUT, Van's used fuel tank sealer to seal the sending unit and we cannot get it off. We called them and they said there is a solvent they sell to dissolve the sealer but we would have to remove the tank to use it??? We are not going to remove the tank. (at least not yet) They suggested we come up with some procedure to try to flex the unit and perhaps it would unstick. My feeling is mechanical devices rarely heal themselves.

So guys, you have come thru so many times in the past, you got a solution for this one?

Click to expand...

Bite that bullet hard and R&R the tank ... faster/safer/sure fix ... rarely in my life does it pay to short cut the steps, and the question is whether an attempt at work-around will just lead to multiplying the problems or complications you don't foresee.

My experience is that removing enough stuff to do the job takes a fixed amount of time. Then fix the sender and replace it. How much time will you save by a work-around before you still have to do the R&R? After an hour or two, you'll still have the basic R&R, but might have other issues from the attempt. The work-around will add unnecessary time that won't shorten the job to be done, IF it fails to work. If you get that solvent on the tank seams will that cause leaks later?

I'm assuming the basic talent is there, and knowledge to R&R the tank. Builder? or 2nd owner? May be a factor. Drain the fuel? (filter it, and consider whether to simply add to the other tank). Fly tank to near empty to minimize excess fuel.

I suspect the SB on anti-rotation bracket for the A/C is not a question? (check and fix it while tank is off). You'll be able to invert the tank/new sender to test free range of motion, and maybe want to pressure chk for leaks before re-installing it?

Whatever - don't over rotate/torque the screw on the new sender wire. Cautionary note on that one. It can damage the sender.

(RV-6A builder and RV-10's may be different in details).

The screws are removed

From your reply I think you assumed that we could not get the screws out.

The screws are out, and the sender flange just sets there only attached by sealant. Should be easy, right?? Won't budge..

I ordered a bottle of polygone to goop on it.. hope that loosens it up...

A little heat with a heat gun and a stiff 1" wide putty knife with a sharpened edge works very well. I popped mine off with very little effort extending my fuel tank capacity on my -9 quick build wings. Aircraft paint stripper works great to clean up the remainder. There is no need to purchase the expensive stuff when a can of this stuff works as good, or better. https://www.amazon.com/Klean-Strip-...861&sr=8-4&keywords=klean+strip+paint+remover
[/url]DSC02040 by David C, on Flickr[/IMG]

Sticking fuel sender

I just constructed my tanks. When bending the sending units I needed to bend the float to clear both the J channel and vent tube. Slightly forward or aft the float would stick against one of the two.

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Perhaps you don't need a new unit, just a slight adjustment of the bend. I agree, a little careful heat from a heat gun should soften the sealant.

Safety wire garrote. Slice the sealant between the parts.

JackinMichigan said:

We sent our leaking fuel tank back to Van's to be repaired. They fixed the leak BUT now the fuel sending unit sticks. It will set at 30 gallons for days then suddenly drop to 12 gallons. It even sticks when filling the tank.

Click to expand...

Wait a minute, Vans's will fix leaking fuel tanks? I had no idea! I'll give them a call.

-Marc

They fixed mine on warranty

I had purchased QB wings, so the leaky tank was their responsibility. It cost me $300 to ship the thing, but they fixed it and shipped it back at no cost. If you do not have the QB wings, I am sure they will do it for a fee.

Some one mentioned the sending unit getting hung up on internal parts. This jogged my memory. After installing the sending unit, I checked it by connecting an ohm meter and turning the wing over. I had an issue on at least one wing with the sending unit getting hung up an had to remove it and bend the float wire. This may be what is causing the hang up now.

Thanks guys, you are great.

When I built my first set of tanks, I missed the step in the drawings that require a very small bend in the portion of the float arm that goes into the portion of the sender that rotates. When calibrating the tank I found my floats would flop all around, thus had to take them off to redo it.

It's a bit of work, but it's a lot faster than removing the tanks completely. As noted before, you should be able to remove the screws and then use a putty knife sharpened and some elbow grease to let you pry off the sender.

In my case, in putting the sender back in on one of the wings I got a small dab of proseal on the cork (and didn't realize it), and after a few days found my float was stuck to the bottom of the inside of the tank. Dreading doing the whole thing over again, I was able to rig a long piece of hinge pin with a little bit of flare to the end to get in via the fuel drain and be able to push up and down on the float arm, and eventually dislodge it. If yours is "sticking", you may be able to do something similar as well.