Spoiled Gas Residue
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After ~5 years, gasoline sours and eventually turns to this foul tar-like residue, destroying the pump, FDM, level sender, & usually the float - if not the tank itself.

A tank can often be salvaged by adding fresh gas (87 octane - never premium) and solvents like Berryman's B12 pour-in, and cleaners like Techron. Especially for 4.9L engines (which are more-sensitive to fuel varnish than others), it's also a good idea to add some top-end lube like Marvel Mystery Oil (MMO) and lead substitute. Filter replacement should be done more-frequently until the tank is clean.

If the varnish has dried, it can often be removed by pressure-washing, followed by vacuuming (with brushing if necessary). Water is very easy to remove when it's the only thing in the tank because the tank can be heated; either by sunlight, incandescent shop-light (drop light), or any type of heater. A steady flow of air into the tank (as by shop vac blowing into the filler neck) speeds drying.

If the tank must be replaced, avoid Spectra & Airtex, which are the worst garbage brands of fuel system parts. Dorman may cost slightly more, but it usually has LLT warranty.

Owner caption July 2024 · Photo 0 of 5000