Hi, Scott to properly fix fuel contamination issues you must start at the source the "GAS TANK" you will need to buy a gas tank rust remover and metal prep solution system, go online and research the different products available, stay away from rust converters and liquid Kreem liners, I recommend POR15 because it stops rust permanently you will also need some nuts and bolts ball bearings etc. and a service manual.
1. Remove the tank and drain all fuel and let dry.
2. Remove petcock and filter or fuel pump and filter.
3. Seal all openings except the top fuel filler opening with tape, plugs, or rubber *******.
4. Fill the tank with a strong solution of Dawn soap and water, seal the opening and shake vigorously for 1 minute and let sit for 30 minutes, remove the gas cap and pour out contents, rinse with a garden hose or pressure washer and let dry thoroughly.
4. Pour in 1/2 cup of nuts, bolts, ball bearings, etc. and seal the opening, shake vigorously for 2 minutes.
5. Open the gas cap and shake out all nuts and bolts along with dirt and rust, use a flashlight to inspect results and repeat as necessary until all rust is removed.
6. Following the directions of your rust remover product begin the procedure of removing residual rust, remember bare metal when dry will start to rust/oxidize immediately so make your last step a final rinse of solvent or kerosene anything that has a petroleum base, your first tank of fuel will mix with the residual solvent and not damage your fuel system.
7. Properly clean or replace all fuel filters, petcock, and fuel lines.
8. Remove and disassemble carburetor/s and properly clean all parts use a carburetor dip if necessary for the really bad ones.
9. For you injected folks use carb cleaner for the injectors and fuel rails and test with battery jumpers for proper function. If you're not in a hurry I recommend the services of Injectorrx.com
For more information about your issue and valuable "FREE" downloads that you will need for viewing or printing please click on the blue links below. Good luck and have a wonderful day.
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