MS-II Second Start Failure
 

I'm trying to get my 1997 UK spec NA MX-5 running on a MS-II that I've built myself. Running the Reverant spark output mod, JBPerf 4 channel board for sequential injection, TIP125 fuel pump driver, opto input for CMP signal and TIP120 idle driver. On 3.1.1 MS2E firmware

I hooked it all up to the car yesterday and she fired up, a bit reluctantly but a bit of throttle got her started and running. She ran like that for about ten minutes, then I switched her off and went to pick up a timing gun on loan to me.

Return with the timing gun, reconnect the MS-II and it won't start. Tried it from cold, from hot, nada. Reconnect the stock ECU and it fires right up, runs and drives just fine.

A bit of investigation seems to show I'm getting no spark. Using the timing gun shows almost no flashes during cranking, only a random flash accompanied by a pop from the exhaust. Also, pulling the No 1 plug lead and laying it on the cam cover doesn't show any arcing during cranking, although this is hard to confirm as I'm doing this solo.

I've checked my harness adapter for continuity on the correct DB37/MX5 pins and all is OK.

What's next to check? I'm using the DIY Autotune basemap for the DIYPNP, altered to increase cranking RPM to 400, and turn on sequential injection and additional drivers. Injector Staging set to Simultaneous, 1 Squirt per Cycle.

Any help would be hugely appreciated

Output test mode is your friend!

So just turn on the output test, set some dwell (default is 3ms, that sounds OK to me?) and lay a plug lead on the cam cover and hit go? Will it automatically try and spark until I turn off the MS again?

OK, Output test done, coil A in TS is firing plugs 2&3, Coil B fires plugs 1&4. Is this the wrong way round?

Yes, you need to swap them.

Wires swapped, car runs. No idea why it's not right, just happy that it works now