Table 4-2. Unit Troubleshooting-continued -706880183

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

Table 4-2 Unit Troubleshooting - Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

FIREFIGHTING SYSTEM - Continued

INSUFFICIENT PRESSURE

Step 1. Follow procedures for engine and pump speed higher than specified for desired pressure

and volume.

Step 2. Check pump speed with tachometer at RPM COUNTER connection on pump operator's

panel. If pump speed is too low, adjust throttle. If proper engine speed cannot be maintained,

refer to engine troubleshooting.

CAUTION

Do not attempt to pump greater volume of water at the desired

pressure than the pump is designed to handle. Exceeding

pump capacity will reduce pressure in an inverse ratio.

Exceeding maximum recommended pump speed will produce

cavitation, and will seriously impair pump efficiency.

PRESSURE NOT RELIEVED WHEN DISCHARGE VALVES ARE CLOSED

Step 1. Check for sticky pilot valve.

Repair pilot valve (see para 4-36).

Step 2. Check for plugged lines.

Remove obstruction or replace line.

PRESSURE WILL NOT RETURN TO ORIGINAL SETTING AFTER DISCHARGE VALVES ARE RE-

OPENED

Step 1. Check for sticky pilot valve.

Repair pilot valve (see para 4-36).

Step 2. Check for main relief valve sticking.

Repair relief valve (see para 4-35).

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