_i. Exterior metal surfaces._ Scrub exterior metal surfaces clean of fuel to prevent fire hazard. Allow to dry before using again. _j. General inspection._ Carefully examine all other parts, adjust as necessary, and replace any which are damaged. 56. SERVICE AFTER SIX FIRING MISSIONS. After the flame thrower has been used on six firing missions or the equivalent in training work, experienced personnel should follow these directions: _a. Before-operation and after-operation service._ Follow the same procedures as in Paragraphs 52, 53, and 55. _b. Test firing (or simulated firing)._ (1) If tactical conditions permit test firing at a suitable test range (Par 15), fill the fuel tanks with fuel. (Pars 37 through 40) (2) If test firing with fuel is impracticable, fill fuel tanks with clean water. (Be sure to dry all parts after test.) (3) _Remove filling-plug assembly._ (Par 69) Fish out the retainer rod and chain by means of a bent wire. (4) Do not unscrew the safety-head plug. (5) Insert the testing plug with 0-to 500-pound pressure gage (plug and gage are from service kit) in the filling-plug opening. Tighten testing plug in seat with wrench. (6) Fully charge pressure tank. (Par 32) (7) If test firing with fuel, load ignition cylinder. (Par 18) (8) Open pressure-tank valve and simultaneously observe pressure in fuel tanks by reading gage. The gage indicates the pressure in both tanks. It should be between 350 and 390 pounds per square inch. (9) Read the gage at the expiration of not less than 5 minutes. The tanks should have a pressure reading of not more than 390 pounds. If the pressure continues to increase beyond 390 pounds and the safety head blows, replace the safety head and the pressure regulator. (10) Fire by operating controls (or simulate firing if tanks are filled with water). The burst should last 3 seconds, during which time the pressure should not drop below 260 pounds. (11) If the pressure does not conform to the requirements stated in (8), (9), and (10), adjust the pressure regulator upward or downward. (Par 67 _d_) (12) While the above test firing is proceeding, check for leaks at all joints and connections on the tank group. The pressure system should be checked by painting the joints with soap-and-water solution and by looking for bubbles which indicate leaks. For replacement of parts where pressure leaks, see Paragraph 66. Fuel leaks may be seen without soap and water. For repair of fuel leaks, see Paragraph 75 _e_. The nozzle should be observed by removing the ignition shield. Nozzle leaks are corrected by cleaning, adjusting needle (Par 75 _d_), or by regrinding. (Par 75 _e_) If this is not successful, replace both needle and barrel as a unit.