Table 4-2. Unit Troubleshooting-continued -706880184

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

Table 4-2 Unit Troubleshooting - Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

FIREFIGHTING SYSTEM - Continued

"HUNTING" (FLUCTUATING PRESSURE)

NOTE

Hunting can result from a combination of suction and discharge

conditions involving the pump, relief valve, and engine. When

the elasticity of the suction and discharge system and the

response rate (reaction time) of the engine, pilot valve, and

relief valve are such that the system never stabilizes, hunting

results. Changing one or more of these factors enough to

disrupt this timing should eliminate hunting.

Step 1. Inspect suction hoses and connections for worn seals or looe connections.

Tighten connections or replace seals in suction hoses (see para 4-1 0 and 4-1 1).

Step 2. Check for sticky pilot valve.

Repair pilot valve (see para 4-36).

Step 3. Check for sticking relief valve.

Repair relief valve (see para 4-35).

SLOW RESPONSE

Check for plugged filter or line.

Clean lines and filter.

FIRE PUMP WILL NOT ENGAGE

Step 1. Check correct switching sequence has been carried out.

Carry out correct switching sequence (see para 2-13).

Step 2. Check for electric shift disengaged.

Push in manual disengage handle (on left hand side of pump body).

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