1994 GMC Van

Remove the engine cover and air cleaner. Relieve the fuel system pressure.
At the injector connector(s), squeeze the two tabs together and pull straight up.
Remove the fuel meter cover and leave the cover gasket in place.
Using a small prybar or tool No. J-26868 or equivalent and a round fulcrum, carefully pry the injector until it is free from the fuel meter body.
Remove the small O-ring from the nozzle end of the injector. Carefully rotate the injector's fuel filter back and forth to remove it from the base of the injector.
Discard the fuel meter cover gasket.
Remove the large O-ring and back-up washer (if equipped) from the top of the counterbore of the fuel meter body injector cavity.

To install:

Lubricate the new lower O-rings with automatic transmission fluid and then push on the nozzle end of the injector until it presses against the injector fuel filter.
Position the injector back-up washer into the fuel meter bore.
Lubricate the new upper O-rings with automatic transmission fluid and then position it over the back-up washer so that it seats properly and is flush with the top of the meter body. Positioning must be correct or the injector will leak after installation.
Install the injector so that the raised lug on the injector base is aligned with the notch in the fuel meter body cavity. Press down on the injector until it is fully seated. The electrical terminals should be parallel with the throttle shaft.
Install the cover gasket and the meter cover.
Reconnect the electrical leads, start the engine and check for leaks.