But you did bring up an excellent point. The M4-ATX has a setting where you can specify the voltage that indicates IGN on. I believe it is set to ON at anything higher than 5.24v I wonder if it is in fact dipping to below that thus causing the rapid on off signals that M4-ATX doesn't like. Im going to have to put a voltmeter on it during crank to see what it dips down too at crank. Also I could put the setting at something like 2 volts.
Either way i think I like the simplicity of the charge lamp controlled relay, keeps the guesswork out of the isolation circuit