The fuel quality hydrometer provides a general indication of fuel quality and should not be considered to be scientifically accurate.

1. Drain the fuel filter housing by following the steps below:

•	Stop the engine.

•	Place a container under the water drain valve exit hose at the left front side of the engine.

•	Open the drain valve.

•	Command the fuel lift pump ON with a scan tool.

•	Fill a 1 liter (0.946 quart) container with a sample of fuel.

•	Close the drain valve.

2. Fill a J 38641-B Diesel Fuel Quality Tester hydrometer with the fuel sample by doing the following:

•	Squeeze the hydrometer bulb.

•	Submerse the hydrometer tip into the sample.

•	Release the bulb, allowing fuel to enter the glass tube until the fluid completely floats the ball inside the tube.

•	Gently spin the hydrometer in order to relieve the surface tension of the fuel sample.

3. Read the scale on the glass tube at the point where the top of the fuel sample makes contact.

•	Reading this value will indicate an approximate fuel oil specific gravity. Refer to tool instructions on how to determine API Gravity.

•	Refer to Fuel Oil Specific Gravity Requirements table.

4. If the correct fuel is being used in the conditions listed in Fuel Quality and meets the number 1-Diesel or the number 2-Diesel fuel oil specific gravity requirements, the fuel may be OK. If not, the fuel should be replaced.