The V8 Owners Forum -

Never assume though !! Always test. A little testing at the start would have had this resolved a long time ago it seems. One of my early questions which went unanswered was whether it was possible for a the single wire between coil positive and the old tacho was capable of supplying 12V to the coil...

Interesting - didn't know the colour was significant. Anyway, sorted now with appropriate notes for any future owner.

White and yellow. Why?

Well, after much testing and puzzling over wiring diagrams from various sources, I finally fixed my ignition non-starting problem. As I thought all along, it was related to my tacho. Running a new cable from an ignition switched source to the coil positive terminal sorted it - and hey presto, the en...

Notice you have one of those horrid pre-insulated crimps to the coil positive. Could the 12v feed have pulled out of that? I'll repeat. It ain't going to work without 12v. No "spare" wires floating around. I have pictures from last year for comparison. Agreed, where the hell does 12V come...

A tacho should receive a trigger from the -ve ie trigger side of the coil...you stated it was supplied from the 12v side ? Have you tested the ecu's outputs as requested ? Sorry, my error. The tacho was originally connected to coil positive, and is now required to be connected to coil negative. ECU...

Ok, the Intermotor 15000 amp connections (on my car) are as follows:

pin 1 to coil negative
pin 2 to battery negative via heatsink
pin 3 to ECU pin 24
pin 4 to coil positive
pin 6 to ECU pin 12

Thanks for the pics. Nothing obvious there. But the coil must get +12v from somewhere. What make/model is the ignition amp module? If I can find details of it might help me understand it. I have seen revcounters connected to the coil positive. There will still be a pulse present there - but not as ...

A tacho should receive a trigger from the -ve ie trigger side of the coil...you stated it was supplied from the 12v side ? Have you tested the ecu's outputs as requested ? Sorry, my error. The tacho was originally connected to coil positive, and is now required to be connected to coil negative. ECU...

I would be surprised if any tacho was taken from the coil positive. It's just a positive...12v, this never changes. Old tachos were taken off the trigger wire ( some may call it a ground...but it's not just a ground....as it goes off/on etc ) If the only changes that were made to the car was the ta...

Further test: After ensuring continuity between the ECU pins 12 and 24 to the amp multiplug (the thin brown and thin black wires visible at the multiplug), there was 1.6V steady at the brown and 0.03V steady at the black, both whilst cranking, at the multiplug end but without being plugged into the ...

Thanks Dave.

The amp (module) multiplug gets 2 x 5V supplies from the ECU, but as soon as that plug it connected to the amp, the voltage disappears! There is no separate 12V feed to the amp in my set-up, hence the confusion with the MoTeC diagram, which says there should be. No 12V at the coil either. The only t...

Nope. 1V when ignition on and still 1V when cranking.

OK, the ECU reads 150 rpm when I'm cranking (also noted injector dwell time registering). Does this mean that the dizzy pickup and feed to the ECU is working then?