Ok, in the Renix the synch sensor in the distributor SHOULD NOT be able to kill the engine, it simply provides data to the ECU for the firing pulse of the injectors and if there is no signal it goes to default mode.
For spark we need the ICM, coil, CPS/CKP crank sensor, B Latch relay, and ECU. When cranking the engine, once the RPMs have reached 300, the crank sensor sends a strong enough signal to the ECU for it to determine the correct firing for the cylinders. No crank sensor data, no spark. If the ECU has poor grounds, no spark. The ECU, the ICM, the o2 sensor, and others ground at the DIPSTICK tube. Clean down to bare metal, treat with anti-corrosion material, and make the connections TIGHT. There is one OEM unibody ground--braided strap rear of head to firewall. Replace the strap with a 4 or 2 ga. cable, same process as for the other grounds--strip down to bare metal, treat with anti-corrosive material, and make tight. Adding a second unibody ground from the negative battery terminal to the fenderwell is a good idea.
Testing for a signal from the ECU to the ICM can't be done without sophisticated equipment.
I will be back from vacation on Monday, if you need some wiring info for the synch sensor in the distributor I can get it from the FSM for the 90 XJ then.
