O-Ring Damage

• Fuel injector replacement and removal may damage O-rings. Installation of the injector into the fuel rail requires pushing the O-ring through a constricted space to properly seat the injector head in the rail. Improper seating and lack of lubrication on the O-ring causes damage to the O-ring material. Small cuts and cracks leak fuel under pressure. Always replace O-rings during fuel injector maintenance. Lubricate O-rings with a coat of new motor oil prior to installation.
  
  

Heat Damage

• Overheated engines may cause O-rings to deform. Superheated rings expand beyond specification, then contract leaving gaps through which fuel passes. Replace O-rings on fuel injectors showing fuel leaks at the head of the injector.
  
  

Age

• Over time, fuel injector O-rings lose their capacity to expand and contract with the heating and cooling of the engine. O-ring material gradually hardens, reducing the capacity to resist pressurized fuel. Leaks developing at the connection to the fuel rail indicate O-ring failure.
  
  

Injector Valve Failure

• Fuel injectors failing to close the internal valve will bathe the combustion chamber with a steady stream of fuel. Investigate engine codes indicating rich air-to-fuel ratios in specific combustion chambers. Rich ratios may indicate failed injectors. Fuel-bathed cylinders have reduced lubrication, causing premature wear and engine failure. Rich combustion may damage catalytic converters when non-combusted fuel burns in contact with the high-temperature catalyst.
  
  

Fuel Pressure

• Fuel pressure beyond specification causes leaks at the O-ring connection of fuel injectors. Test the fuel pressure to determine if the leak is a result of too much pressure or general failure of seals.