I'm converting a Honda iGX700 engine to run on hydrogen for my research project and would like help understanding my engine's breather system to see if it would be sufficient for the hydrogen conversion. Articles online recommend having crankcase ventilation for a hydrogen engine since hydrogen can leak more easily into the crankcase and cause unwanted explosion. My engine currently has a breather in the crankcase that connects to a "diaphragm tube" that then goes into the low pressure side fuel pump and then the inlet manifold. Why is the tube going through the low pressure fuel pump and not directly to the inlet manifold assuming it's a regular PCV system? Is the pressure from the crankcase also being used to pump the fuel into the high side pressure pump? Also, when I run the engine on hydrogen instead, is it ok to use the existing breather system as crankcase ventilation or should I add another PCV valve to the valve cover?

Attached are a couple of diagrams of the low pressure fuel pump system and breather system.



Breather system in the crankcase. It doesn't show if the Diaphragm tube actually comes out of this.

The diaphragm tube is what I assume comes out of the breather system. The purge tube connects to the inlet manifold. Fuel tube is where the fuel enters and Fuel tube B is where the fuel feeds to the high pressure pump.