912 ignition troubleshooting

Yes, grounding the ignition switch wires disables the ignition.

When did the engine last run? Have you got known good components that are configured correctly?

It is not unknown for both ignition modules to fail at cranking speeds. What happens is that the first one fails but is undetected because the engine is started by the remaining module that is still working. When that one eventually fails then that is when you realise that you have 2 faulty modules. I always start my engine on a singe module and I alternate between L & R so that I always test the each one can operate at cranking speeds.

You can try heating (air gun) or cooling (ice pack) the modules to see if that helps. I would also check the pick up coil gaps, the HT coil connections and the earths.

I bought the engine used and I have never run it. I am trying to eliminate everything before I purchase new modules. I verified that the grounding switches are correct and I have traced through all the wiring and everything is correct per the heavy maintenance manual. I checked the coils today and I have no resistance on the primary side of all 4 coils. Secondary side checks good and primary to secondary side tests good. I know the reading is small so I have my ohm meter set as low as it will go, 2000 and I am getting a reading of 0.00 on all 4. hoping this is the issue as its the cheaper one to solve. Finding it weird that all 4 coils are the same though.

If you are measuring the primary side of the coil, your reading is not an indication of a problem. The spec is 0.3 to 0.05 ohms and your meter reading of 0.00 ohms is probably a tolerance error in your meter.  The problem would be very high resistance or an open circuit primary coil.  While you are at it, check the secondary side of the coil, and between the primary and secondary side as per the specs in the MMH.  

Good to know on the tolerance of the meter. the other sides checked out. I just did the ice trick on the modules and it fired up. I'll be getting a new set. 

There are 2 other potential solutions for you. You can send your modules to Carmo Electronics in the Netherlands to be repaired or you could fit the Ignitech replacement Rotax modules.

I've had mixed results with Carmo where I've had to send units back a second time for repair. On the other hand I've never heard a bad report of the Ignitech modules, they are easy to fit and have an extra module to assist when starting.