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Discussion Starter · #1 ·
Installed a new sending unit in the gas tank (stock tank) of my 48 Chevy p/u. When I fill it completely full gas now leaks out from around the sending unit. I noticed one or two of the screws wouldn't tighten all the way down but was hoping there was enough pressure on the others that it would be okay...nope. I have to take the sending unit back out to adjust the arm some and was wondering the best way to be able to secure it so it won't leak. Obviously don't want to be drilling and retapping with fuel around and was hoping someone here knew of quick/easy way of doing this. I appreciate any help. Thanks in advance.
 

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silicone will not work for any length of time with fuel.
are the threads buggered in the tank or is it because the screws bottom out in the hole,or do the holes go right through the tank flange? there is a new gasket under the sending unit right? maybe a thicker gasket would help. you will need to use all the screws that the factory put in though. maybe a regular sheet metal screw would get a bite and work, (assuming they were machine screws that were factory). are there broken off screws? do the threads in the holes just need to be cleaned up with a tap? does the new sending unit have the same thickness of flange where the screws go through? if it is thinner then that could be why the screws are bottoming out before they get tight. that would just mean a few washers under the screw heads.
usually when i work on a tank, i take it out of the vehicle for ease of working and inspection. no use fixing a rusty bottomed tank. i usually fill it completely with water, to displace any fuel vapour, and then do whatever work is required. when all done it can easily be pressure tested. I usually drain the water and let it sit for a bit so water droplets have a chance to find their way to the drain, i then plug the outlet line and dump in a gallon or so of varsol, to get rid of remaining water droplets. the tank can be rolled around to ensure the varsol gets everywhere, then stand it up and let it sit for a minute or two, so the contents can settle out (varsol is lighter than water so it floats on top, but needs a minute to settle out) then open the outlet and drain all the varsol/water. allow to sit for a few minutes, then flush with some methyl hydrate to ensure all the water is out. (methyl hydrate is the same as gas line antifreeze, it breaks down the surface tension of a water droplet so it will mix with the fuel so it can make it's way through an orifice-like a jet in a carb. in this circumstance it will mix with the water droplets and help them to find their way out of the tank). i usually install a new fuel filter after a bit of running. that way anything that got loosened up has had a chance to get caught in the old filter.
good luck.
 

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Discussion Starter · #6 ·
I think I'm going to try and combine some of your ideas. The silicone I was thinking about trying is the gray auto silicone, I think it will hold up okay. Trucknut I was thinking what you suggested, although I was considering a little bit larger screw, sheet metal screw or self tapping. Thanks to everyone for the ideas....I'll let you know how it turns out.
 

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i think you will have problems with silcone. it may last a little while, but it isn't made to be in fuel all the time. maybe the gasket eliminator would be a better choice, but not sure if it is made for fuel either. look on the permatex site for more info maybe.
 
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