Installation/removal of fuel injectors on several Mazda models requires ensuring that one releases the fuel system pressure and removes the negative battery cable to install/uninstall the fuel injectors. In the MX-3 with 4-cylinder engine and in 1990-94 323, Protege, detach electrical connectors at injectors, remove the fuel injector harness and remove the delivery pipe with injectors and pressure regulator. Isolate the injectors and the delivery pipe assembly. Installation requires replacement of the fuel injector O-rings with clean engine oil and fitting of the injectors to the delivery pipe and connecting the injector wiring. In the case of the 1995-97 Protege, the processes are the same, such as the removal of throttle cables and fuel lines and the fitting of the new O-rings and grommets correctly. In the case of the 626/MX-6/Probe with 2.0L and 2.2L engines, release pressure, disconnect the battery and remove the required parts in order to reach the injectors. Replacing O-rings and proper seating and alignment of injectors. In the case of the 2.3L engine, a thorough procedure of removing various parts and putting on new O-rings along with assembling all the related lines and electrical connections are required. Once it has been installed, be sure there are no leaks by switching the ignition on. The test procedures include turning on the engine, listening to the injectors and resistance measurement in case no sound is made, making sure that it was within the values specified.