Gasoline direct injection (GDI) is a more advanced version of multiport fuel systems, where fuel is injected directly into the combustion chamber instead of the intake port. Direct injection improves combustion efficiency, increases fuel economy, and lowers emissions.
Both systems use electronic fuel injectors to spray fuel into the engine, but the difference is where they spray the fuel. With port injection systems, fuel is sprayed into the intake ports.
With direct injection, the injectors are in the cylinder head and spray fuel directly into the combustion chamber, mixing with the air charge. The intake only supplies air to the combustion chamber with direct injection.
Since direct fuel injection requires high fuel pressures to overcome combustion pressures created in the engine’s cylinders, a typical high-pressure fuel pump can produce in the neighborhood of 2,000 psi maximum fuel pressure, depending upon operating conditions.
High-pressure direct injection poses some unique safety issues. Because any liquid pressurized to 2,000 psi can literally cut like a knife, a technician should be mindful that recommended safety procedures must be used to bleed off the extremely high fuel pressures present in the injector rail. Some manufacturers recommend disabling the fuel pump with the bi-directional controls included with most scan tools, then starting and running the engine until it stalls. Other manufacturers prefer alternate methods, so it pays to research applicable service information before attempting to diagnose or repair any GDI system.
Due to safety issues, manufacturers require that all seals and most high-pressure steel fuel lines be replaced if removed for injector replacement or any related service repair as they are “one-time use” components and cannot be reused. Take extra care when replacing seals and do not bend or damage the high-pressure line when servicing these style fuel injectors.
This video is sponsored by Standard Motor Products.
