Table 5-2. Direct Support Troubleshooting - Continued
TEST OR INSPECTION
PUMP FAILS TO PRIME OR LOSES PRIME
Step 1. Air Leaks.
Use the following procedure to locate air leaks:
Connect suction hose to pump and attach suction cap to intake end of hose.
Close all pump openings.
Open priming valve and operate primer until vacuum gauge indicates 20 to 22 in. Hg
(508 to 559 mm). (If primer fails to draw specified vacuum, it may be defective, or
leaks are too large for primer to handle.)
Close priming valve and shut off primer. If vacuum drops more than 1 0 in. Hg (254
mm) in 1 0 minutes, serious air leaks are indicated. With engine stopped, air leaks are
If leaks cannot be heard, apply engine oil to suspected points and watch for break in
film or oil being drawn into pump.
Connect suction hose to hydrant or auxiliary pump. Open one discharge valve and run
in water until pump is completely filled and all air expelled. Close discharge valve,
apply pressure to system and watch for leaks. A pressure of 100 psi (690 kPa) is
sufficient. DO NOT EXCEED RECOMMENDED PRESSURES.
If pump has not been operated for several weeks, packing may be dried out. Close
discharge and drain valves and cap suction openings. Operate primer to build up a
strong vacuum in pump; run pump slowly, and apply oil to impeller shaft near packing
gland. Also, make sure packing is adjusted properly.
Step 2. Faulty wiring.
Check all wiring to the priming pump and valve for loose terminals, damaged insulation, or
broken wire strands, especially near terminals.
Step 3. Mechanical failure.
If priming pump does not operate, remove priming motor and manually turn rotor shaft. It
should turn freely without binding. Unless the priming pump is properly maintained, sediment
in the water being pumped may cause it to stick.