Table 4-2. Unit Troubleshooting-continued -706880182

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

Table 4-2. Unit Troubleshooting - Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

FIREFIGHTING SYSTEM - Continued

ENGINE AND PUMP SPEED TOO LOW AT FULL THROTTLE

Step 1. Check that relief valve is set correctly.

Refer to Direct Support maintenance level.

Step 2. Insufficient engine power.

Engine requires maintenance; refer to Direct Support maintenance level.

ENGINE AND PUMP SPEED HIGHER THAN SPECIFIED FOR DESIRED PRESSURE AND VOLUME

Step 1. Check suction strainer, suction scre ns, or impeller vanes for debris.

Remove suction strainer and hose, and clear away all debris. Pressure backwash (preferably

in parallel or "volume" position) will usually clear impeller vanes when pump is stopped.

Step 2. Check for defective suction hose.

On old suction hoses, the inner liner sometimes becomes so rough it causes enough friction

to prevent pump from drawing full capacity. Sometimes, the liner will separate from the outer

wall and collapse when drafting. It is usually impossible to detect liner collapse, even with a

light. Try drafting with a new suction hose; if pump then delivers capacity, it may be assumed

that previous hose was defective. Replace defective hose.

Step 3. Check that suction hose correct size.

When pumping at higher than normal lifts, or at high altitudes, use a larger suction hose.

Step 4. Pump impellers or wear rings badly worn.

Refer to Direct Support maintenance level.

ENGINE SPEED HIGHER THAN SPECIFIED FOR DESIRED PRESSURE AND VOLUME

Check gear selection of transmission.

Ensure transmission is in "drive".

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