Sleeve Metering Fuel System (SMFS) Fuel Flow Schematic
(1) Fuel priming pump (closed position). (2) Fuel priming pump (open position). (3) Return line for constant purge valve. (4) Constant purge valve. (5) Manual purge valve. (6) Fuel injection nozzle. (7) Fuel tank. (8) Check valve. (9) Check valve. (10) Check valve. (11) Fuel inlet line. (12) Water separator. (13) Fuel filter. (14) Fuel line. (15) Fuel transfer pump. (16) Fuel bypass valve. (17) Camshaft. (18) Fuel injection pump housing.
Fuel from fuel tank (7) is pulled by fuel transfer pump (15) through water separator (12) (if so equipped) and fuel filter (13). From fuel filter (13) the fuel goes to fuel injection pump housing (18). The fuel goes to fuel injection pump housing (18) at the top and goes through an inside passage to fuel transfer pump (15).
From fuel transfer pump (15), fuel under pressure, fills the fuel injection pump housing (18). Pressure of the fuel in fuel injection pump housing (18) is controlled by fuel bypass valve (16). Pressure of the fuel at Full Load is 205 ± 35 kPa (30 ± 5 psi). If the pressure of fuel in fuel injection pump housing (18) gets too high, fuel bypass valve (16) will move (open) to let some of the fuel return to the inlet of fuel transfer pump (15).
Flow Of Fuel Using The Priming Pump (SMFS)
When the handle of fuel priming pump (2) is pulled out, negative air pressure in fuel priming pump (2) opens check valve (8) and pulls fuel from fuel tank (7). Pushing the handle in closes check valve (8) and opens check valve (9). This pushes air and/or fuel into fuel injection pump housing (18) through the fuel passages and check valve (10). More operation of fuel priming pump (2) will pull fuel from fuel tank (7) until the fuel lines, fuel filter (13) and fuel injection pump housing (18) are full of fuel. Do this until the flow of fuel from manual purge valve (5) is free of air bubbles. Later model SMFS engines are not equipped with a constant purge valve. On later model engines the excess fuel flow will return to tank (7) through fuel bypass valve (16).
Constant Purge Valve (SMFS Only)
Constant Purge Valve
(4) Constant purge valve. (D) Check valve.
At high idle, the constant purge valve (4) lets approximately 9 gallons of fuel per hour go back to fuel tank (7). This fuel goes back to fuel tank (7) through return line for constant purge valve (3). This flow of fuel removes air from fuel injection pump housing (18) and also helps to cool the fuel injection pump. Check constant purge valve (4) makes a restriction in this flow of fuel until the pressure in fuel injection pump housing (18) is at 48 ± 7 kPa (7 ± 1 psi). Later model engines are not equipped with a constant purge valve. Any excess fuel flow will return to fuel tank (7) through fuel bypass valve (16).