Fuel sending unit

[rossco]

Having issues with replacement fuel sending unit. (100-4) Have reported problem to supplier. Instructions explicitly stated screws that were supplied go through flange and into the tank. That was not the case with my original tank. My bad, didn't check to see if that was the case. Original screws (shorter) only threaded into flange. The new screws (longer) when driven into the holes separated the flange from the sheet metal of the tank. My dilemma is this; how do I re-attach the flange to the sheet metal? Can I use a cordless drill on an open fuel tank?

 

[Keoke]

I guess it could be done. But I would take the tank to a radiator repair shop and have it reattached like it was originally.-JMOP

 

[steveg]

Seem to recall that the 100-4 had a loose flange that could fall into the tank. If that's the case it could maybe be fished up toward the opening and restrained with a couple of longish pieces of 10-32 threaded rod (unless the threads are different). The sender could be dropped down over these rods and attached with a couple of screws; the rods would then be removed and the other screws attached. Just a guess - the flange on my 100-6 is attached on the inside of the tank.

I've had good success against leaking with hylomar and bonded washers: https://www.pbase.com/stevegerow/image/44018072

 

[Michael Oritt]

If the holes in the flange are threaded the screws are probably making the flange stand off from the tank. Try drilling out the flange holes and that should allow you to pull the flange flush against the tank surface.

I have had best results simply using a fresh cork gasket with no sealant. On one occasion I tried using Hylomar and it wound up in the tank. Luckily it was captured in the inline fuel filter before it got to the fuel pump which probably would have been ruined by the sealant.

 

[steveg]

I have had best results simply using a fresh cork gasket with no sealant. On one occasion I tried using Hylomar and it wound up in the tank. Luckily it was captured in the inline fuel filter before it got to the fuel pump which probably would have been ruined by the sealant.

I should have said - "use hylomar sparingly". Just smear a light coating on either side of the gasket - not enough to drip into the tank. Am also using #8 bonded washers around the screw heads with hylomar as the fuel can weep out through the screw threads.

Was suggesting this because the stock gasket seems to deteriorate as there have been a lot of leakage complaints online over the years. My setup's been leak-free since 2005.

Thinking about this - maybe hylomar or not on the gasket is irrelevant and the real problem is the screws extend into the tank and with the stock setup there's nothing to keep fuel from weeping out the screw heads except the fit of the screw threads going through the gasket.