Fuel Specific Gravity Testing

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

1. Drain the fuel filter housing by following the steps below:
   1. Stop the engine.
   2. Place a container under the water drain valve on the bottom of the fuel filter.
   3. Open the drain valve.
   4. Fill a 1 l (0.95 quart) container with a sample of fuel.
   5. Close the drain valve.
2. Obtain a J 38641-B  Diesel Fuel Quality Tester.
3. Fill the hydrometer with the fuel sample by doing the following:
   1. Squeeze the hydrometer bulb.
   2. Submerse the hydrometer tip into the sample.
   3. Release the bulb, allowing fuel to enter the glass tube until the fuel completely floats the glass bulb inside the tube.
   4. Gently spin the hydrometer to relieve the surface tension of the fuel sample. Read the scale on the glass bulb at the point where the top of the fuel sample contacts the scale. By reading this value, the value will give an approximate fuel oil specific gravity. Refer to tool instructions on how to determine API Gravity.
4. Refer to the Fuel Oil Specific Gravity Requirements table. If the correct fuel is being used in the conditions listed in Fuel Quality, and meets number 1-Diesel or number 2-Diesel fuel oil specific gravity requirements, fuel is OK. If not, the fuel should be replaced.