Operation

TM 5-4240-501-14&P CARBURETION Fuel Pumps Operation Operation of the fuel pump is illustrated in Figs. 119, 120 and 121. Any restriction in the fuel or vacuum lines will affect operation. Also any leaks that cause air to get into the fuel line or reduce vacuum in the vacuum line will reduce performance. Fig. 119 Fig. 120 - Fuel Flow with Crankcase Pressure Fig. 121 - Fuel Flow Crankcase vacuum To service fuel pump, pump should be removed from carburetor or mounting bracket. When removing fuel supply line from tank to pump, be sure to plug fuel line or turn off fuel valve, if so equipped. Disassemble fuel pump by removing four (4) 1/4" head cap screws from pump cover. Separate pump cover, pumping chamber and impulse chamber. Discard old gaskets, diaphragms and springs. Clean pump parts in carburetor solvent or lacquer thinner. A repair kit is available. See Illustrated Parts Lists. The kit includes all parts needed. Install chamber gasket using locator pins. Place springs in spring recesses and install pump diaphragm locator pins. Place pump chamber body on impulse body using locator pins. Place damping diaphragm and cover gasket on pump body. Install cover and four (4) screws. Torque screws to 10- 15 in. lbs. (.12-.17 mkp, 1.13-1..69 Nm). See Fig. 119 for exploded view. FUEL PUMPS, ECCENTRIC OPERATED To Replace Pump Diaphragm Remove pump from cylinder and then remove four screws to separate pump head from pump body. With a narrow punch, drive lever pin out until pump lever is loose. Pin may then be driven in either direction, but need not be removed entirely. Remove old diaphragm, but leave diaphragm spring in pump body. Place new diaphragm into pump body with the slot in shaft at right angles to the pump lever. Diaphragm spring should fit into the cup under the diaphragm. Without the lever spring, insert the pump lever into body holding the diaphragm down. Fit the hook at the end of lever into the slot in diaphragm shaft. Fig: 122. Assemble Fuel Pump Align holes in lever and body, then drive lever pin into place. Place lever spring into body with inner end of spring over the projection in pump body, then use a screw driver to force outer end of spring into body until it slips over the projection on lever. Fig. 122, Illus. 2. Place pump head on body and partially insert the four screws. Press pump lever down as far as possible and then tighten the four screws. 34