GMC 1994 Yukon Owner's Manual page 254

To drain water:
1. Stop and park the vehicle in a safe place. Turn off the engine and apply
the parking brake.
2. Remove the fuel tank cap.
3. Place a fuel-resistant container under the filter drain hose.
4. With the engine
off, open the
water drain valve
2 to 3 turns.
When standing in
front of the
vehicle, the valve
is located on the
right side of the
thermostat
housing.
5. Start the engine and allow it to idle until clear fuel is observed.
6 . Stop the engine and close the water drain valve.
7. Remove the fuel-resistant container and properly dispose of the
contaminated fuel. To find out how to properly dispose of contaminated
diesel fuel see "What to Do with Used Oil" in the "Engine Oil (Diesel
Engines)" part, later in this section.
8. Install the fuel tank cap.
If the WATER
IN FUEL
light comes on again after driving a short distance
or the engine runs rough or stalls-a large amount of water has probably
been pumped into the fuel tank. The fuel tank should be purged.