Adjusting Carburetor, L.P. Fuel System

TM-5-4240-501-14P Special Diver Air Support System (SDASS) NSN 4220-01-292-3708 Manual
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TM 5-4240-501-14&P indicating fuel is flowing into regulator. Put soap suds on the outlet again. Then slowly turn adjusting screw at bottom of secondary regulator counterclockwise until a bubble forms at the outlet. Then turn adjusting screw in (clockwise) slowly until soap bubbles on outlet no longer form. Hold adjusting screw at this point and tighten locknut. Press primer button to allow fuel to flow. Release and again put soap suds on outlet to make certain the fuel shuts off. Repeat several times. If bubble should form after primer button is released, the adjusting screw should be turned in until flow stops and soap bubble does not break or enlarge. Loosen fuel line between regulators. Reassemble secondary regulator to carburetor with short rubber fuel line in place. Tighten fuel line, Fig. 110. Adjusting Carburetor, L.P. Fuel System See Fig. 110. Loosen locknut on load needle screw and turn needle screw in until it seats. Do not force; open 2-1/2 turns. Turn idle needle in until it seats, then open one turn. If engine will not be required to idle, leave idle needle closed. Depress the primer button momentarily, then start engine, run engine to allow it to warm up before final adjustment. With engine running at normal operating speed, turn the load needle screw in slowly (clockwise) until engine starts to miss (lean mixture). Then turn load screw out slowly past the point of best operation until engine begins to run unevenly (rich mixture). Then turn load screw in just enough so engine will run smoothly. Hold load screw and tighten locknut. Hold throttle at idle position, then release throttle. Engine should accelerate quickly and smoothly. If engine will be required to run at idle, turn the idle speed adjusting screw on throttle until engine runs at proper idle speed for engine model. See Check Chart. Hold throttle at this point and turn the idle slowly in or out until engine runs at maximum idle speed. Then re-adjust idle speed screw until proper idle speed is obtained. Allow throttle to open. Engine should accelerate quickly and smoothly. If not, re-adjust load screw, usually to a richer mixture. To stop engine, turn off fuel supply valve at fuel cylinder. CARBURETION L.P. Fuel and Kerosene Fig. 110 - Adjusting Carburetor, L.P. Fuel System Starting Engine To start engine, do not use choke, but depress primer button momentarily, then start engine immediately. In cold weather, it may be necessary to partially close the carburetor choke valve to permit the engine to run smoothly until the engine warms up. Cleaning L.P. Gas Filter (Optional) Unscrew filter head from filter body. Remove element assembly from the head. Fig. 111. Wash the element in commercial solvent cleaner or gasoline. If the accumulated dirt is gummy, we suggest a short soaking period in solvent cleaner. The element should then be rinsed in clean gasoline and blown with compressed air. ALWAYS USE REVERSE FLOW FROM THE INSIDE OUT. NEVER USE COMPRESSED AIR ON THE OUTSIDE SURFACE OF THE ELEMENT. NEVER DIP ELEMENT IN "BRIGHT DIP" OR OTHER ACID SOLUTION. 31

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