2-21. OPERATING FROM FIRE HYDRANT (Continued).
Turn engine throttle control knob (3, figure 2-1) counterclockwise to accelerate engine until master pressure
gauge (9) indicates desired discharge pressure.
As a precautionary measure, the master pressure gauge reading (9, figure 2-1) should not be
permitted to drop below 10 psig. This will permit a 5 psig error in gauge accuracy with the
danger of collapsing a water main. It may be necessary to sacrifice the discharge pressure in
order to prevent damage to a water main.
Turn pressure relief control knob (12, figure 2-1) counterclockwise to decrease pump discharge operating
pressure, clockwise to increase pump operating pressure.
Fire pump will heat up rapidly if pump is operated with all discharge valves closed. Prolonged
operation will cause damage from overheating.
Periodically check engine temperature gauge (1, figure 2-1) for normal engine-operating
temperature range of 100ºF (55.5ºC) to 250ºF (138.8ºC).
If a shutdown is required for changing hoses or any other reason, slow the engine to decrease
water pressure to 30 psi and close the discharge valves. Open tank-to-pump valve control
handle (13, figure 2-1) and tank fill control handle (14) to recirculate the water.
Shut down fire pump by turning engine throttle control knob (3, figure 2-1) clockwise to throttle engine down.
Turn heat exchanger control switch (20, figure 2-1) to the "OFF" position.