Section IX. MAINTENANCE OF FUEL SYSTEM

TM5-6115-584-12 NAVFAC P-8-622-12 TO-35C2-3-456-1 TM-05682C-12 Section IX. MAINTENANCE OF FUEL SYSTEM 4-18. DESCRIPTION AND FUNCTION. a. Low Pressure System (see Schematic figure 1-5). (1) Fuel pump may draw fuel from an external source to fill set tank or set tank may be filled man- ually. If an external fuel source is selected, a float valve assembly in the set tank maintains the fuel level in the tank. Two other fuel pumps (in series) draw fuel from the set tank and force the fuel through a primary strainer, two filters, and a check valve assembly, to the injection pump. b. High Pressure System. (1) Fuel tnjection pump forces the fuel, under high pressure, to the fuel injection nozzles. The in- jection nozzles provide fuel to each combustion chamber of the engine. Unused fuel is returned from the injectors to the fuel tank. A cam and gear on the camshaft drives the fuel injection pump. The gear drives the pump face gear, providing fuel distribution to each cylinder in the proper order. The cam oper- ates the pump plunger, pressurizing fuel to the noz- zles. A control sleeve meters fuel by controlling the length of time the plunger spill port is closed, main- taining pressure, and therefore, the amount of fuel delivered in each stroke. The pintle type injection nozzles are conventional inward opening with ad- justable opening pressure. They are factory adjusted t o open at 1900 to 1950 psi. 4-19. FUEL TANK ASSEMBLY, a. Inspection on Equipment. Refer to paragraph 3-13a. b. Removal (see figure 4-7). Drain fuel into suitable container by opening drain valve. Tag and disconnect fuel hoses from fuel tank fittings. Disconnect electrical lead from electrical connector (10). Remove nut (1) and flatwasher (2) from straps (3) on outside of fuel tank. Remove tank from skid-base. On ASK equipped generators, remove top panel, left side panel and side closure (Refer to paragraphs 5-4, 5-5, and 5-12). c. Disassembly. (1) Fuel Level Gauge. Unscrew and remove fuel level gauge (5) using tools only on the hex portion of the gauge. (2) Float Switch. Unscrew collar and disconnect electrical connector (10) if not previously discon- nected. Unscrew and remove float switch (6) using tools only on the square portions of the switch. (3) Unscrew and remove fittings (7). (4) Holding pipe adapter (11) with a wrench, un- screw and remove drain valve (8). 4-16 Change 7 (5) Loosen filler cap and remove filler cap (4) and strainer (5). d. Cleaning and Inspection. (1) Tank. Clean tank exterior using suitable sol- vent and clean cloth and brush. Inspect tank for signs of physical damage. If damaged refer to higher level of maintenance. (2) Fuel Level Gauge. Check that fuel level gauge face is clean and readable. Check that as cork float is moved up and down, the meter movement rotates. (3) Float Switch. Inspect terminal connector for damage to threads. Check to see that float slides on shaft without binding. Clean with suitable solvent if required. (4) Fittings. Inspect fittings for good leak-free seating on tank and check threads for physical damage. (5) Fuel Drain Valve Assembly. Check that drain valve does not leak and threads for physical damage. e. Test. (1) Float Switch. Remove float switch (6) from tank (9). Using an ohmmeter, check for continuity between terminals A and B of Switch (see figure 4-8). Switch should show no continuity when float is up. Switch should close when float drops to 2-7/8 ±3/16 inch from threaded collar of float switch. Re- place switch if it does not operate properly. (2) Tank. If tank shows signs of physical dam- age or leaks refer to higher level of maintenance. f. Reassembly (see figure 4-7). (1) Fuel Drain Valve. Engage threads of fuel drain valve assembly (8) 1/2 turn into fuel tank adapter (11). Coat threads with sealing compound MIL-S-22473. Tighten valve assembly into adapter (11). (2) Fittings. Engage threads of fitting (7) l/2 turn into fuel tank (9). Coat threads with sealing com- pound MIL-S-22473. Tighten fittings into tank. Fit- tings should face Generator Set for proper connection of fuel lines. Attach fuel lines to fittings. (3) Float Switch. Engage threads of float switch (6) 1/2 turn into tank (9). Coat threads with sealing compound MIL-S-22473. Tighten float switch (6) into tank using tools only on square portion of switch. At- tach electrical lead to connector (10) on top of float switch and tighten.