"If the engine is hot, place mixture control in IDLE CUT-OFF, switch auxiliary fuel pump to ON for 30 to 60 seconds, then OFF. Return mixture to full rich and continue with cold start procedure."
When performing this procedure, check the fuel flow guage. The FF should not register when you have the mixture at ICO and the boost pump on. If you see any indication of fuel flow, some fuel is flowing past the spider (the round silver distibutor at the top of the engine) into the intake manifold. 30 seconds of this could be a lot of fuel, so I tend to skip the next prime (that found in the cold start procedure) and start cranking.
There is a little rubber gasket in the fuel control unit, and unless its just been overhauled, it'll always leak a bit at ICO. I havent yet seen a IO-520 that didnt register some fuel flow at ICO.
Bevan..