To carry out an injector circuit test, first disconnect the wiring from each injector. Measure the resistance between the two terminals of each injector with an ohmmeter and renew any off specification injectors. Following this, connect a test lamp to each injector wiring connector one by one while the starter motor operates; the test lamp will flash at each connector. In the event that the engine control relay and fusible links do not work, check them. In the event the lamp doesn't flash on one or more terminals, check the wiring from the connector to the ECU, checking that the terminals on the ECU are clean and making contact. If no faults are found, a fault may be indicated in the ECU and so ECU power supply and earth circuits should be checked. If the test light flashes at each connector, the circuit works properly. To test injector working, plug them back in, start engine, and disconnect each injector one at a time for not more than five seconds, it should misfire each time. If not, the injector is blocked or sticking, and before removing the injectors for testing and perhaps cleaning (which requires special equipment), the ignition high tension circuit should be checked. To remove and install the fuel supply hose, you should reduce fuel system pressure, remove the bolts and disconnect the fuel supply hose and discard the O ring. In order to facilitate the release of fuel pressure in the system, loosen the fuel filler cap to prevent pressure build-up in the tank. If the vehicle is fitted with a fuel pressure regulator, disconnect the vacuum hose from the fuel pressure regulator. Next, release the clamp and disconnect the return line. Unplug the wiring connectors from the fuel injectors, then remove the retaining bolts and pull out the fuel rail and injectors from the engine, preventing the injectors from dropping. Extract the injectors from the fuel rail and discard the O rings and grommets; remove the insulators from the inlet manifold. To install, repeat removal, renew the O rings, and grommets, lubricate these with fuel and install the injectors squarely in the fuel rail. After tightening the torque of the fuel rail retaining bolts, connect the return line and vacuum hose. Always use a new O ring for the fitting of the fuel supply hose. Also, make sure the wiring is connected to the injectors. Ultimately, assess for external leakage within the fuel system and adjust the fitting of the spacers between the fuel rail and inlet manifold. Finally, re-fit the fuel rail and injectors.