Fuel injectors are often needlessly replaced when they develop a leak. Unless the body of the injector is leaking, which is rare, replacing the O-ring seals is all that is needed. It is also a good idea to clean the injectors when repairing leaks, and it is also best to clean and service all the injectors at the same time. The injectors are all held in place by a common injector-rail. To remove one injector requires removing the rail. Doing so removes them all.
Raise the hood of the car an inspect the fuel injector rail while the car is running at idle. A strong odour of gasoline is a good indicator that there is a fuel leak. Look carefully, however, at the top and bottom of the fuel rail. Use caution: Fuel injection systems are under high-pressure and gas spraying out of the injector seal is highly combustible.
Shut the car off immediately if a leak is present. Remove the fuel pump fuse, wrap the leaking injector with a shop towel to soak up the gasoline and start the car. Allow the car to run until it stalls. This step relieves the fuel pressure in the fuel rail and the rail can safely be removed.
Disconnect the injector wiring harness and remove the fuel rail bolts that hold the rail in place. Remove any associated fuel lines or hold-down clamps that will prevent the rail from being lifted up to unseat the fuel injectors from the engine. Once it is loose, lift the rail up and remove each of the injectors. They are held in place by snug-fitting O-rings and are easily pulled out. It is not necessary to keep them in order.
Remove the upper and lower O-ring seals on the injectors. Place the injectors in a carburettor soaking basket and drop the basket in a bucket of carburettor cleaner. Allow the injectors to soak for several hours to thoroughly clean them of carbon deposits. After soaking, rinse the injectors with clean water and immediately blow them dry with compressed air.
Install new O-rings. Make sure the O-rings are designed for use with gasoline and fit the vehicle being serviced. Standard O-rings will quickly deteriorate and fail. Lightly coat the injectors with petroleum jelly and insert them into the fuel rail.
Fit the lower part of the injectors back into the ports in the engine and bolt the rail back into place. Reattach any clamps or fuel lines. Install the fuel pump fuse and start the engine. Inspect the injectors while the car is running and make sure there are no leaks.