Table 4-2. Unit Troubleshooting-continued -706880181

TM 5-4210-233-14&P-1

Table 4-2. Unit Troubleshooting - Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

FIREFIGHTING SYSTEM - Continued

PUMP FAILS TO PRIME OR LOSES PRIME - Continued

Step 7. Check for a clogged orifice in the oil line at the fitting of the priming pump head.

Refer to Direct support maintenance level to remove obstruction from orifice.

Step 8. Check vane primer pump.

After prolonged service, wear may increase primer vane clearance and reduce efficiency.

Refer to Direct support maintenance level to adjust.

Step 9. Check valve in by-pass line stuck open.

If a bypass line is installed between the pump discharge and water tank to prevent pump

from overheating with all discharge valves closed, look for a check valve in the line. If valve is

stuck open, clean it, replace it, or temporarily block off line until a new valve can be obtained.

Step 10. Estimate or measure vertical distance from water source to pump.

Do not attempt lifts exceeding 22 vertical feet (6. 7 m) except at iow altitudes and with

equipment in new condition.

Step 11. Check that end of suction hose is deep enough.

Although suction hose might be immersed enough for priming, pumping large volumes of

water may produce whirlpools, which will allow air to be drawn into suction hose. Whenever

possible, place end of suction hose at least two feet below water surface.

Step 12. Check that suction line is below pump.

If possible, avoid placing any part of suction hose higher than pump suction inlet. If high point

cannot be prevented, close discharge valve as soon as pressure drops, and reprime. This

procedure will usually eliminate air pockets in suction line, but it may have to be repeated

several times.

Step 13. Primer not operated long enough.

Refer to operating instructions for required priming time. Repeat priming procedure.

NOTE

The maximum time for priming should not exceed one-half

minute for lifts up to 10 feet (3. 05 m).

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