Mercury Optimax Diagnostic Guide., Page 5Get this manual
OPTIMAX DIAGNOSTIC GUIDE
Procedure 2
FUEL INJECTORS
Six fuel injectors (1 per cylinder) are used to provide fuel from the fuel rail to the direct injectorsThe fuel injectors are mounted in the fuel railIf fuel injector or injector o-ring is leaking, fuel will enter the air pressure side of the railA simple test is to connect pressure gauge to the fuel pressure test port and turn the ignition key to the "ON" position
NOTE: Prior to making this test prime the fuel system using the primer bulb on the fuel supply hose to confirm that the Vapor Separating Tank (VST) is filled with fuelThe electric fuel pumps should run for aboutsecondsThe fuel pressure should rise to approximately 276310 kPa (4045 psi) when the pumps are runningWhen the pumps stop the pressure should level off to approximately 138171 kPa (2025 psi) and holdIf the pressure drops below 138 kPa (20 psi) quickly, it is an indication of fuel leakIf fuel leak is identified, complete these steps: Remove the fuel retainer nutsRemove the water outlet hose (port rail only)Slide both port and starboard rails away from the cylinder head (keep the direct injector in place inside the headTurn the ignition key to the "ON" position to pressurize the system and look for fuel leaks at the fuel injector openingsReplace any leaking injectors