When you need to seal a fuel gauge sending unit...

Question:

My question pertains to a 1987 Dodge Dakota truck’s fuel tank. When removing the gas gauge sending unit out of the fuel tank there is a material that is used by the factory to seal the top (the exposed side of the unit). The substance is, or reminds me of, packing material of a heavy anaerobic nature.

In my hometown I questioned auto paint stores, body shops, and the dealership. Everybody knows about the substance however nobody knows the correct replacement material to use. Can you help?

Answer:

I don’t know exactly what material was used to seal the fuel gauge sending unit in your truck but can offer some general advice regarding how to seal the units. A common mistake people make is using a silicone-based product to seal sending units because silicone will be broken down by contact with gasoline. All of the major sealant products companies make sealants that are designed specifically for contact with gasoline. Two good examples of gasoline compatible materials that will work with your sending unit are Form-AGasket and MotoSeal #29132, both of which are from Permatex (permatex.com).