Test Procedure
WARNING: This page is about a different variant/trim than selected.
- Turn ON the J 44175 Fuel Composition Tester. See Special Tools .
- Verify the fuel composition tester is operational by measuring the AC frequency output with a DMM. Refer to Measuring Frequency . A frequency without a fuel sample in the test cell indicates that the tester is working correctly.
- Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal .
- Close the bleed valve on the fuel pressure gage.
- Place the bleed hose (1) of the fuel pressure gage into the 100 ml beaker (2).
- Command the fuel pump ON with a scan tool.
- Slowly open the bleed valve on the fuel pressure gage until an adequate fuel sample is obtained.
- If water appears in the fuel sample, replace the fuel in the vehicle. Refer to Fuel System Cleaning .
- Pour the fuel sample from the beaker (1) into the J 44175 until the level of the fuel is at the top of each fuel test port (2). See Special Tools .
- Observe the diagnostic LEDs on the fuel composition tester. If the red fuel diagnostic LED is illuminated, a fuel contamination condition exists. Refer to Fuel System Cleaning .
- Measure the output frequency of the fuel composition tester.
- Subtract 50 from the reading on the DMM to obtain the percentage of alcohol in the fuel sample. Refer to the examples in the following table.
- If the fuel sample contains more than 10 percent ethanol, replace the fuel in the vehicle.
IMPORTANT:
Bleed the fuel pressure gage a few times in order to obtain an accurate fuel sample.
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 a misdiagnosis.
Fuel Composition Test Examples
| - | Frequency (Hz) | Subtract 50 | Ethanol Percent |
|---|---|---|---|
| Example A | 50 Hz | -50 | 0% |
| Example B | 65 Hz | -50 | 15% |
| Example C | 129 Hz | -50 | 79% |