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5.1.2 Pump Priming Problems
Table 12. Pump Priming SCR Table
Pump Loses Prime
Or Will NOT Prime
Electric Priming System No recommended engine speed is required
to operate the electric primer. However, an
engine RPM of 1,000 will maintain the elec-
trical system while providing enough speed
for initial pumping operation.
Defective Priming System Check the priming system by performing a
“Dry Vacuum Test” per NFPA standards. If the
pump holds vacuum, but primer pulls less
than 22 (± 2) inHg of vacuum, it could indi-
cate excessive wear in the primer.
Suction Lift Too High Do NOT attempt lifts exceeding 22 ft.
Restricted Suction Strainer Remove obstruction from suction hose
strainer.
Suction Connections Loose
Or Dirty
Clean and tighten all suction connections.
Check suction hose and hose gaskets for
possible defects.
Primer NOT Operated Long
Enough
Proper priming procedures should be fol-
lowed. Do not release the primer control be-
fore assuring a complete prime.
Air Leaks Attempt to locate and correct air leaks using
the following procedure.
1. Perform dry Vacuum Test on pump per
NFPA standards with 22 (± 2) inches mini-
mum vacuum required with loss not to ex-
ceed 10 inches of vacuum in 5 minutes.
2. If a minimum of 22 (± 2) inches of vacuum
cannot be achieved, the priming device or
system may be defective, or the leak is too
big for the primer to overcome (such as an
open valve).
3. After priming, shut off the engine. Audible
detection of a leak is often possible.
4. Connect the suction hose from the hydrant
or the discharge of another pumper to pres-
surize the pump with water, and look for visi-
ble leakage and correct. A pressure of 100
psi (6.9 bar) should be sufficient. Do not ex-
ceed pressure limitations of pump, accesso-
ries, or piping connections.
5. The suction side relief valve can leak. Plug
the valve outlet connection and retest.
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