GMC 2.8L Duramax Diesel 2020 Manual page 38

2. Place a container under the
filter drain valve. The filter drain
valve is on the bottom of the
fuel filter. The filter drain valve
is under the vehicle on the
driver side, inside the
frame rail.
3. For van models, open the drain
valve by turning it
counterclockwise. Allow the
filter to drain until all of the
water has been removed.
Close the valve.
For pickup models, open the
fuel filter cap by turning it two
to three turns. Allow the filter to
drain until all of the water has
been removed. Close the cap
hand tight.
4. Properly dispose of the water
contaminated fuel.
5. Start the engine and let it run
for a few minutes. During the
draining process, air may have
entered the fuel system. If the
engine stalls, the fuel system
may need to be primed. See
Fuel Priming following.
Fuel Priming
For the fuel system to work properly,
the fuel lines must be full of fuel.
If air gets in, the fuel lines need to
be primed before operating the
vehicle and the Fuel Operated
Heater (FOH).
If air is present, the following may
have happened:
The vehicle ran out of fuel.
The fuel filter was removed.
The fuel lines were removed or
disconnected.
The fuel filter water drain valve
was opened while the engine
was running.
The FOH pump and FOH fuel
lines were removed or
disconnected.
The system is not harmed by air in
the fuel lines; however, the engine
and/or the FOH may not start until
the fuel system is primed and the air
is removed.
Driving and Operating
Priming the Fuel System
There is an electric priming pump
that will bring fuel to the engine and
eliminate air in the fuel lines. To
prime the engine:
1. Correct any condition that
caused the loss of prime.
2. Turn the ignition on for
30 seconds. Do not start the
engine. The fuel pump will start
priming.
3. Turn the ignition off, then back
to start, and crank the engine
for 15 seconds.
4. If the engine does not start,
repeat Steps 2 and 3 until the
engine starts.
If the engine does not start
after repeating Steps 2 and 3
three times, turn the ignition
key off for 60 seconds.
5. Repeat the above steps until
the engine starts.
6. If the engine starts, but does
not run smoothly, increase the
engine speed slightly.
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