Some alternators need to be exited to start working, there is a third terminal on them to do this. One way of doing this is to put an oil pressure idiot light switch in the circuit between the battery and the the alternator, as soon as the oil pressure up it turns off the exiciter current. The other way that I used on my 8n conversion is to open the throttle until the alternator exicited itself, somewhat easier than adding an additional circuit.