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Home >> GMC >> 2003 >> Jimmy 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing - 4.3L >> Fuel Systems >> Alcohol/Contaminants In Fuel Diagnosis Without Special Tool >> Test Description

Test Description

Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no-start, or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel injection system and cause a misfire in that cylinder. If fuel system is contaminated with water, inspect fuel system components for rust or deterioration.

Alcohol concentrations of 10 percent or more in the fuel can be detrimental to fuel system components. Alcohol contamination may cause fuel system corrosion, deterioration of rubber components, and subsequent fuel filter restriction. Some types of alcohol are more detrimental to fuel system components than others. Ethanol is commonly used in gasoline, but in concentrations of no more than 10 percent. Some fuels, such as E85, contain a very high percentage of ethanol. Fuel with more than 10 percent ethanol may cause driveability conditions such as hesitation, lack of power, stalling, or no-start.