I've answered many questions recently about older vehicles (pre-2005) having fuel system issues. As a car collector, I have encountered fuel system issues myself, almost all of which stem from the use of ethanol blend fuels, such as E10.
Whereas vehicles manufactured in the past ten years are specifically designed to accommodate a broad variety of fuels (especially "Flex Fuel" vehicles), ethanol poses a special problem to older vehicles.
- Many vehicles manufactured more than a decade ago use fuel tanks that will rust in the presence of moisture. Ethanol fuels, when allowed to sit for extended periods in conditions where heat and humidity are high, catalyze moisture to condense at the top of the gas tank, eventually collecting on the sides and bottom of the gas tank when the temperature again falls, causing rust spots to develop throughout the tank.
- Most engine computer controls that are over a decade old are not equipped to deal with the peculiar sensor readings caused by ethanol blend fuels, causing the fuel mixture to be made richer than necessary, and retarding the timing to avoid pinging. This notably lowers performance and fuel economy.
- Carbureted engines with older carburetors may experience a gelatinous buildup in the float bowl, which may eventually clog the metering jets. This gelatine-like buildup is residue from water combining with other contaminants in the fuel system, and isn't permanently harmful, but can cause misfiring and loss of performance.
- Use of ethanol blend gasoline in older cars can cause permanent harm to components of the fuel system, including the fuel pressure regulator and the fuel injectors.
- Change your fuel filter regularly, and be certain that your fuel pickup strainer does not become clogged with rust particles. (If your variable speed fuel pump is constantly operating at high speed, this is a good indication that your pickup strainer is clogged);
- If your fuel has been sitting in the tank for more than one year without being used or added to, GET RID OF IT and replace it with fresh fuel. NOTE: If you buy a car that shows evidence of sitting idle for an extended period, even on a used car lot, expect to replace the fuel, first thing.
- Use a FUEL INJECTOR CLEANER additive with every two or three fill-ups. Use with every fill-up if your vehicle sits for longer than a month at a time.
- Use a FUEL SYSTEM WATER REMOVER (sometimes called "FUEL SYSTEM MOISTURE REMOVER") at least four times per year. (WARNING: This may cause the above-described gelatinous slime to develop if you have water in your fuel system. Fear not, if you have a fuel-injected engine, the gelatinous gunk will pass through the system eventually, to be burned in the cylinders or ultimately expelled from the exhaust);
- IF POSSIBLE, USE NON-ETHANOL FUEL IN ALL OLDER VEHICLES. It costs more and, in some areas, is not available. In this case, the introduction of a METHANOL-BASED fuel additive may help, and fuel system water remover additives are essential.