I've found that leaving the throttles slightly open and then hitting CTRL E will start the engines. I Just  hit Ctrl 4 times and the engines slowly come to life. I've got one of those Saitek yoke setups with the quadrants and found that If I pull the throttles all the way back the engines will cut off. That's when I figured that there must be some relation to throttle position. Sure enough, for me at least, that was the solution.