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Our 1995 Cadillac Fleetwood Brougham unfortunately suffered disuse for several years.

It would now start when fed starter fluid spray, but would not continue running, so the fuel pump and/or relay were suspect.

After removal of the plastic gas tank, with plan to replace the in-tank fuel pump and filter,

flushing yielded gummy gel, as well as other odd-colored crap and water.

My guess is that acid dip would damage ther plastic tank,

and I'm concerned for the condition of in-tank baffles.


I don't know of anyone who cleans this type of tank.


Can anyone advise a proper way to clean and treat the tank,

since a new one is not available, and would be extremely costly if it were.

Another used one from a junkyard would probably be no better than what I have.

By the way, over the past nearly 10 years, I've only used non-ethanol gas in all our modern and vintage cars

exept if inavailable during cross-country travel.


I appreciate any advise and suggestions as far as how to do a good job of cleaning the tank,

and what materials would do a safe and thorough job. 

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My best suggestion is visit your nearest farm animal vet and get yourself one of those wonderful rubber gloves that that goes all the way up your arm to the shoulder then follow these instructions https://www.youtube.com/watch?v=Liiewkf1UIA 


Don't have any southern state gummy jell experience, so I don't know how long gas lasts in the warm verses the cold, but in my chilly part of the world gas tank goo usually means new injectors, purge valve and at least one vacuum check valve.  Hopefully a clean tank with new pump will give you trouble free down the road driving. 

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Watch the tip you use, as you don't want to cut through the plastic. 😲


But I think that is a good suggestion, pressure wash with detergent feed. At least the in tank pump tanks I have seen are large enough in the opening to get your hand in there and clean the sump area.

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Plastic gas tanks are a multilayer laminate to prevent evaporation and have gasoline resistance on the inner layer.  The majority of the tank is polyethylene, but the inner layer probably isn't, and is more polar like maybe sulfonated polyethylene. 


Start with water-based materials and a lot of mechanical character to the cleaning.  The detergent wash is a good idea - use warm water to improve solubility.  In general, most olefinic plastics are more easily damaged by hydrocarbon solvents than by aqueous acids and bases.  If you have to use a hydrocarbon to get the goop out, I'd use gasoline since the tank was designed to hold it.  An acid is likely to leave both the tank and the goop unimpressed, but bugger any metal it can find.


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