Hi All, My number 4 injector isn't firing and I'm wondering if I can use a standard LED test light as a noid light. If so testing at the injector end of the loom seems pretty straight forward but to test from the ECU I am a little confused about. Seeing as the injector is fired by a switched earth, do I need to connect one end to a live 12v and the other to the #4 injector pin on the ECU? Thanks in advance. Dave
#4 Injector If you check out Diagnostic Procedure No.34 in the Nissan Factory Service Manual it will explain the injector circuitry. The injectors have a constant 12VDC feed from one of the fusible links. This means you should have battery voltage on one of the two wires to each injector all the time. You can check the integrity / resistance in this section of the wiring by disconnecting the battery & measuring the wiring from the fusible link to the injector plug using the ohms function. There should be virtually no resistance. The ECU switches the earth circuit to each injector. According to the FSM the earth circuit for No.4 Injector terminates on Pin No.112. Once again to test this circuit, measure the resistance of the wiring between Pin No.112 & the injector plug. As far as noid lights & test lights go. They are used as a quick means of identifying if a circuit is intact. Because a noid light illuminates, does not necessarily indicate the circuit is serviceable, as resistance isn't measured. If there is any resistance in the circuit, perhaps caused by corroded connections, it will not be identified. Obviously, if the noid light doesn't illuminate, there is a problem. The other test to be done would be to measure the resistance across the pins of the injector. If you have an automotive stethoscope, & place it on the injector, an audible click should be apparent if you remove the CAS & rotate it by hand.
Warning! Attention! I quoted Pin No.112 in the above post. This was gained from the wiring diagram in Diagnostic Procedure 34. There is a discrepancy in the procedure, as Pin No.110 is identified as No.4 Injector in the test. Please DOUBLE CHECK the information & use the wires colour code!
Also be aware that you are playing directly with a output from the ECU and if you draw too much current through it, you may need to repair or replace your ECU. THERE ARE NO FUSES TO SAVE YOUR ECU in the event something goes wrong.
Thanks for the response guys. Haha, I don't have the old ECU Graham. It's OK though, I'll pull the one out of the old Zed and try it. A dead injector driver would be the best outcome as far as repairs go but this is a Zed and we all know that best outcomes are rare lol. Wishing you all a Happy New Year Cheers, Dave
Still no clicking from #4 injector with another ECU. I don't have time to mess with it any more today but it's either a short or a dead injector. I'll fight through tomorrows hangover and get the multimeter on it. Cheers
Put a fuel pressure gauge on the fuel line after the filter. Start the car to build fuel pressure. Switch off, Unplug the injector from the loom Then fire off the injector with 12v directly from the battery check if the fuel pressure drops. If it does, Injector is good. so must be wiring fault. Just touch the terminals quickly so the entire contents of the rail don't empty into the cylinder. They had all been tested and cleaned not long ago but as we know that's no guarantee. Might be as simple as plug being faulty.
