2009 Polaris Sportsman 850 XP EFI EPS Service Manual, Page 58Get this manual
ELECTRONIC FUEL INJECTION Fuel PumpFuel Tank Installation
123456789Reinstall the fuel tank assembly through the right sideConnect the fuel line to the fuel pump outlet and connect the fuel pump electrical harnessReinstall the vent line to the tank fittingInstall the (2) fuel tank mounting screws and tighten securelyInstall the (4) screws into the bottom portion of the righthand footwellInstall the front cab assembly (see Chapter "Front Cab")Remove the shop towel from the fuel tank inlet, reconnect the fuel fill hose and tighten hose clamp securelyInstall the front rack assembly (see Chapter "Front Rack")Install the front mud guards (see Chapter "Mud Guards")When the key switch is on, the fuel rail is pressurized, and the EFI relay provides voltage to the injectorsDuring engine operation, the ECU completes the ground circuit, energizing the injectorsThe valve needle in the injector is opened electromagnetically, and the pressure in the fuel rail forces fuel down through the insideThe "director plate" at the tip of the injector contains series of calibrated openings which directs the fuel into the intake port in cone-shaped spray patternThe amount of fuel injected is controlled by the ECU and determined by the length of time the valve needle is held open, also referred to as the "injection duration" or "pulse width"It may vary in length depending on the speed and load requirements of the engine