Although diesel fuel and water do not readily mix, fuel does tend to entrap moisture from the air each time it is moved from one container to another. Eventually every diesel fuel system collects enough water to become a potential hazard. Fortunately, when it's allowed to settle out, the water will always drop to the bottom of the tank or filter housing. Some models are equipped with a fuel filter that has a water drain (a bolt or petcock at the bottom of the housing). Others are equipped with a water separator, located in front of the fuel tank under the right side of the vehicle. It's purpose is to allow water to settle from the fuel right at the tank and to alert the driver when draining is required. When the water level in the separator reaches a certain point, a sensor turns on the glow plug indicator light on the dashboard, causing it to blink continuously.
On models up to and including 1984, water is usually drained from the filter. On most 1985-89 models, water is removed from the fuel system by means of a water separator.
See Figures 1 and 2Fuel Filter
- Place a pan under the drain to catch the water and fuel.
- If equipped, loosen the vent bolt/screw on the filter mounting base. If there is no vent, loosen the return line at the injection pump (the line that is not connected to the filter).
- Loosen the drain bolt or valve. When fuel flows in a clean stream, close the drain and tighten the vent or return line.
- Raise and safely support the vehicle. Remove the fuel filler cap.
- At the separator, connect a hose from the separator drain to a catch pan.
- Open the drain valve (3 turns) and drain the separator until a steady stream of fuel flows from the separator, then close the valve. Don't forget to install the filler cap.