Chevrolet T-Series Owner's Manual page 180

If the light comes on, use this chart to determine
what action to take.
Water In Fuel Light
Problem
Light comes on
intermittently.
Light stays on
at temperatures
above freezing.
Light stays on
at temperatures
below freezing.
Light stays on
immediately after
refueling, and a large
amount of water was
possibly pumped into
the fuel tank.
180
Recommended Action
Drain water from the
fuel filter.
Drain the fuel filter
immediately. If no water
can be drained and the
light stays on, see your
dealer for assistance.
Drain the fuel filter
immediately. If no water
can be drained, water
may be frozen in the
water drain system or in
the fuel lines. Move the
vehicle to a warm location
to thaw out, and then
drain the filter system.
Fuel tank purging is
required. See your dealer
for assistance.
Notice: If you drive when this warning
indicator is on, you can damage your fuel
injection system and your engine. If the
indicator comes on right after you refuel, it
means water was pumped into your fuel tank.
Turn off your engine immediately. Then,
have the water drained at once.
The frequency of water draining or element
replacement is determined by the contamination
level in the fuel. Inspect or service the collection
bowl for water daily and replace the element
as shown in the Maintenance Schedule. See
Scheduled Maintenance on page 269 for change
interval information.