If you hear a hissing noise while removing the
fuel filter cap, either the vent filter is plugged, the
vent line is restricted, or the vent valve is
restricted. The vent filter is located behind the
coolant surge tank.
Replace vent lines or vent line filter
Replace vent valve (para. 3-25).
Diesel fuel is sensitive to temperature. All diesel
fuel has a certain amount of paraffin-like
components which have high energy value and
help improve fuel economy. When temperatures
are less than 20°F (-7°C) these components
begin turning into wax flakes that can build up on
the fuel tank strainer or in the fuel filter. If wax
build-up is found, replace the fuel in the tank with
a winter grade of fuel if available. You will have
to remove the fuel tank if you need to inspect the
tank strainer (para. 3-25).