C 1500 Yukon 2WD V8-5.3L VIN T (2002)
Fuel: Testing and Inspection
Alcohol/Contaminants-In-Fuel Diagnosis (W/ Special Tool)
TEST DESCRIPTION
Fuel quality can effect vehicle performance. Gasoline and gasoline blends that are contaminated or contain excessive amounts of alcohol can effect
vehicle driveability, fuel economy, fuel system components and emissions. Excessive alcohol in the fuel 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 percent
of ethanol. Fuel with more than 15 percent ethanol may cause driveability conditions in vehicles such as hesitation, lack of power, stalling, or no start.
If excessive alcohol in the fuel is suspected, then use the following procedure to test the fuel quality.
TEST PROCEDURE
CAUTION: Refer to Fuel Gage Leak Caution in Service Precautions.
1. Turn ON the J 44175 Fuel Composition Tester.
2. Verify the fuel composition tester is operational by measuring the IAC frequency output with a DMM. Refer to Measuring Frequency in
Diagnostic Aids. A frequency without a fuel sample in the test cell indicates that the tester is working correctly.
3. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal.
IMPORTANT: You will need to bleed the fuel pressure gage a few times in order to obtain an accurate fuel sample.
4. Close the bleed valve on the fuel pressure gage.
5. Place the bleed hose (1) of the fuel pressure gage into the 100 ml beaker.
6. Command the fuel pump ON with a scan tool.
7. Slowly open the bleed valve on the fuel pressure gage, until an adequate fuel sample is obtained.
8. If water appears in the fuel sample, clean the fuel system and replace the fuel in the vehicle. Refer to Fuel System Cleaning.
IMPORTANT: Do not allow any substances other than gasoline, ethanol/gasoline blends, air, or acetone into the test ports of the fuel composition
tester. Contaminants in the fuel composition tester could result in misdiagnosis.
