Fuel Tank: Testing and Inspection

IMPORTANT: Before attempting the Fuel Tank Leak Check place a dry chemical, Class B, fire extinguisher near the work area.

1. Install the J41415-40 fill tank cap adaptor.
2. Connect the J41413 [1][2]EVAP pressure/purge diagnostic station to the fill tank cap adaptor.
3. With a scan tool, seal the EVAP system.
4. Raise the vehicle on a hoist. Refer to Vehicle Lifting Caution in Service Precautions.
5. With the [1][2]EVAP diagnostic station, maintain 15 in. Hg (3.75 kPa) within the fuel tank.

IMPORTANT: It may be necessary to partially lower the fuel tank to inspect the top of the fuel tank and fuel sender assembly O-ring. Refer to Fuel Tank Replacement.

6. With the J41416 ultrasonic leak detector, test for leaks in the fuel tank and [1][2]EVAP pipes.
7. Visually inspect for fuel leaking from the fuel tank.
8. If a leak is detected in one of the following components, refer to the appropriate procedure:
^ For a fuel tank leak, refer to Fuel Tank Replacement.
^ For a fuel sender O-ring or fuel sender leak, refer to Fuel Sender Assembly Replacement
^ For a fuel or [1][2]EVAP pipe leak, refer to Fuel Hose/Pipes Replacement (Chassis).

ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS
Alcohol concentrations more than 10 percent in fuel can be detrimental to fuel system components and may cause driveability problems such as hesitation, lack of power, stall, no start, etc.

The problems may be due to fuel system corrosion and subsequent fuel filter plugging, deterioration of rubber components, and/or air-fuel mixture leaning.

Various types and concentrations of alcohol are used in commercial fuel. Some alcohol is more detrimental to fuel system components than others If an excessive amount of alcohol in the fuel is suspected as the cause of a driveability condition, the following procedure may be used to detect the presence of alcohol in the fuel.

TESTING PROCEDURE
The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear. If the sample appears cloudy, or contaminated with water, as indicated by a water layer at the bottom of the sample, this procedure should not be used, and the fuel system should be cleaned.
1. Using a 100 ml specified cylinder with 1 ml graduation marks, fill the cylinder with fuel to the 90 ml mark.
2. Add 10 ml of water in order to bring the total fluid volume to 100 ml and install a stopper.
3. Shake the cylinder vigorously for 10-15 seconds.
4. Carefully loosen the stopper in order to release the pressure.
5. Re-install the stopper and shake the cylinder vigorously again for 10-15 seconds.
6. Put the cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid separation.

If alcohol is present in the fuel, the volume of the lower layer, which would now contain both alcohol and water, will be more than 10 ml. For example, if the volume of the lower layer is increased to 15 ml, this indicates at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat higher because this procedure does not extract all of the alcohol from the fuel.