Ignition circuitry - 2 Group ECU

[number 7]

Hi all, I'm trying to troubleshoot the 2 Group ECU in my TVR 400SE. Its Rover V8 based, with a locked distributor providing the trigger to the ECU. Been running fine since installation 16 years ago. However,a few weeks ago, the ignition light came on and remained on whilst driving. The tacho started jumping around as well - 2 to 3 K up and down - engine was behaving normally though, although the voltmeter in the car was reading slightly higher than normal. I replaced the alternator which cured the warning light but not the tacho. I had the tacho rebuilt, although that's probably just a symptom of the underlying problem. Car now will not start, and there is no spark. Replaced coil and ignition amp (the latter twice), and checked wiring continuity. Trouble is, my wiring doesn't seem to follow the pin guide from the manual, e.g. there's supposed to be a live feed from ignition to the amp (module in the diagram)and I think normally to the coil (although that's not shown). There is no voltage at the coil when ignition is on. There is 5V at the amp end of both wires from the ECU pins 12 and 24, but as soon as the amp multiplug is inserted into the amp itself, this voltages drops to nothing. Totally confused! I've also tried to test the dizzy magnetic pickup (Lucas 35 type), and the resistance across the pickup coil is 3,325 ohms. The only reference online I can find for this spec is 500 to 1500 ohms, so I'm not sure if mine is too far out to even work. Any gurus see anything obvious? The diagram at the foot of the image is my circuit on the car.

[AdamW]

What is the part number on your ignition module? Do you have any method to read from the ecu - i.e. The hand controller or pc modem?

[number 7]

Hi Adam, the amp is an Intermotor 15000. I use a laptop to access the ECU, but no error codes.

[number 7]

I've also just tested the cranking when the ECU is connected to my laptop, and I can see the engine was spinning at 150 rpm, so presumably this is coming from the dizzy pickup. More confused now.

[AdamW]

Yes, checking RPM in software was going to be my next advice. So that confirms the engine position sensor (dizzy pickup) is fine.
The intermotor 15000 is what most call a "bosch 008". Here's how they should be wired:


I assume in your case the 12V to pin #4 might come from pin 12 on the ECU? It is not common on modern ECU's to supply the 12v but they might have done it that way back then. That pin 12 might also only be live when the engine is cranking/running so if coil and ignitor dont appear to have 12v when stationary, check again when cranking.