2001 Polaris SLH, Virage PWC Factory Service Manual, Page 148Get this manual
CarburetionExhaust Fuel Pump Operation
The pump supplies fuel to carburetorsOn three cylinder models two fuel pumps supply fuel to each of the end carburetors and commonly to the center cylinderWhen the piston is on the upstroke cran kcase pressure is low, the diaphragm in the fuel chamber moves outward toward the chamber coverThis causes negative (low) pressure in the fuel chamberThe check valve on the fuel supply side of the chamber opensallowing fuel to enterThis vacuum causes the outlet check valve to close so fuel cannot return from the carburetorSee III1III1 Piston on upstroke Inlet check valve open Outlet check valve closed