Jaguar Repair: 1986 xjs no injector signal, resistor pack, logic probe

Question
Hi Howard, Thanks a million for the diagrams. I repaired the wiring to my injectors and also better understand the system and the other parts involved now. I was reviewing some of the other questions and answers and was wondering if the "reluctor" in the distributor is what actually sends the signal to the ecu to fire the injectors and how would it be tested or am i heading way toward left field with this. All resistance values seem to coincide with each other, same on all 12 inj and across the resistor pack

Answer
Hi Larry,
The ignition reluctor triggers the ignition system to ground and disconnect the coil and the ECU does look at that signal to know how often to trigger injectors. If you don't have any ignition then the ECU will not trigger injection. But if you have ignition then that is all that the ignition system needs to do (if that ignition pulse is seen at the ECU) Your diagram should show you which pin that is in the ECU plug. You need a "Logic Probe" to do testing at the ECU. I got one from Radio Shack that works well. Be sure to get one that handles 12v as they have them for different voltages. A logic probe can monitor signals without interrupting the signal.

The injector resistor pack powers the injectors and the ECU grounds the injectors to open them. As I remember the RPM signal tells the ECU how often to ground the injectors and all the other items of the injection system tells the ECU how long in mili-seconds to keep the injectors open and each injector triggers two times on each cylinder and operates either in sets of 3 or in sets of 4. I don't remember which. The injection pulse is not sequential, meaning it does not fire the injectors in the firing order. It only uses the ignition signal as an RPM signal.

Howard