MicroSquirt.com read only forum (Jan.15,2018)

MS-II, V3.0, points triggered, coil control using high current driver, buick v8

I'm getting no spark from my coil. I'm using direct coil control via the high current driver. Points are being used as my tach input to pin #24 (through the relay board). I finally got an RPM signal using the points and a 1000 ohm resistor. (megatune reads 144 RPM when cranking, does this look right?) The Pertronix ignitor unit I originally wanted to use (and made a post about it) would not work on the tach input, no matter how I wired it. Anyway, I've doubled checked assembly instructions and verified the correct jumpers and components are installed for the high current driver. I used the sample settings from MS 2.25 for ignition and dwell setup. I have:
Ignition input Capture - rising edge
Cranking Trigger - Trigger rise
Coil charging scheme - standard
Spark output - going high (inverted)

I did not touch dwell settings, but they look like what should be a good start from what the 'configuring megasquirt' section says. Also, the plastic nut on Q16 (VB921) started to melt. Does this mean I was shorting someting out and allowing it to overheat? Must I use the modified stim to check VB921 operation?

I spent 16 hours yesterday trying to sort out problems with the ignition, including 'accidently' shorting the power supply and a trace on the back of the relay board. oops. But after half a day I got MS-II and the relay board 'working' again and ended up in the same place I was in the morning....no spark. But at least now I have a tach signal, so the day wasn't a total waste. As usual, any and all help is appreciated.

the plastic nut on Q16 (VB921) started to melt. Does this mean I was shorting someting out and allowing it to overheat?

usagoal,

Yes, that's a reasonable bet.

Must I use the modified stim to check VB921 operation?

Either that or remove the coil and put an LED tester in its place (#6 here: http://www.megamanual.com/ms2/V3trouble.htm).

Lance.

Thanks for the reply, I'll do those tests ASAP. As far as the dwell settings go, could one of the options not allow me to get spark? Thanks.

I made the LED tester and used it on the relay board to check operation of vb921 (+) to 12 volts and (-) to S5 (VB921 output) . I do get a pulse which means it should spark!? Does it matter if I keep the LED tester in place along with the (-) coil wire while checking the coil for spark? I don't think it should. I used a different spark tester attached to the coil and still nothing. The coil works (I tested it on my fathers old firebird) so i know that's not the problem. Everything should be set up correctly, but yet still no spark. The only way I was able to get some kind of spark was to ground the coil manually with a screwdriver from (-) coil to the engine block. Though I had to do this rapidly, I did get a few sparks in the tester. It just seems like I'm having a grounding issue with the VB921? or possibly a dwell setting that is not correct? I'm following the manual but with little to show for it. Help is appreciated! Thanks!