Table 4-4. Organizational Troubleshooting Chart - continued

TMS-4210-224-14&P

Table 4-4. Organizational Troubleshooting Chart.(Continued)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

12. FIRE PUMP WILL NOT ENGAGE.

Inspect for leaks in air system.

Locate and repair leaks as required (leakage, if external, maybe detected audibly.)

13. FIRE PUMP WILL NOT PRIME OR LOSES PRIME.

Step 1. Check electric priming system for adequate electric current.

Increase engine speed as required. Engine rpm should be adequate to maintain truck electrical system while

providing enough speed for initial pumping operation.

Step 2. Check priming system for defects. If pump is tight, but primer pulls less than 22 inches (558.8mm)

vacuum, it could indicate excessive wear.

Replace priming pump (paragraph 4-69).

Step 3. Check for air leaks.

Attempt to locate and correct air leaks.

CAUTION

Tighten packing only when the pump is primed and running at low speeds. Always allow slight

leakage of water through the stuffing box to insure against over-tightening of the packing.

Check pump packing during attempt to locate leakage. If leakage through the packing becomes

excessive, a light tightening of the knurled plunger is the only adjustment required.

14. LEAK AT FIRE PUMP PACKING.

Check if pump packing adjustment is loose.

CAUTION

Tighten packing only when the pump is primed and running at low speeds. Always allow slight

leakage of water through the stuffing box to insure against over-tightening of the packing.

Tighten the knurled plunger. Install new packing by removing the threaded cylinder head and

injection plunger.

4-31