My genset fires up ok but quits after 12-15 seconds. Initially gives a code 3 (service) fault. Using the start/stop switch at the generator I get either a 15 fault code for under frequency, or maybe a 36 fault code. Starting the unit with it quitting, the light blinks 3 times. Pressing the stop it blinks 6 times, although a brief pause between blink one and then 5 blinks, then repeats without giving me the 3 initial blinks which I tend to diagnose a 15 fault.  
Is there any way to increase the speed? Do I need to clear a fault which is causing it to not stay running?
Any other suggestions?

I have changed the oil and filter and air filter.