5. FUEL SYSTEM MXU 500 IRS Fit a new O-ring in to the float chamber groove securely. O-ring O-ring Small Convex Accelerating Pump Cover Assemble the accelerating pump diaphragm and new O-ring. Install the accelerating pump diaphragm with the small convex facing up. Accelerating Pump Diaphragm Accelerating Pump Diaphragm 5-18