Fuel flow divider, perhaps?
The fuel flow divider is the fuel spider at the top of your engine...a round metal object with each injector line going to the cylinders. It should have one inlet line, and one small injector line to each cylinder, and one overboard vent line. Inside the divider is a diaphram and a spring. If the diaphram ruptures, it leaks, and fuel should be found draining from the overboard port on the fuel flow divider, of from the drain line (if one's attached to it). If you don't have a drain line (you should...it's a fire hazard), you may see blue or green stains under the fuel flow divider...a sure sign of leakage.
Failure of the fuel flow divider diaphram can cause engine failure...on the ground, or in flight. If you're boosting it the engine isn't starting check for any discharge at all in drain line or port...if you see any fuel there at all, you have a problem and should not operate the aircraft.