Fuel injection system must maintain high pressure... at least 40PSI when
engine is off... If the pressure falls below that, the liquid gas is allowed
to boiled off into gaseous stage from hot engine. Hence the Vapor Lock.
Gaseous fuel is very difficult to push along the line so hard starting
occurs until the fuel cool down/ engine cools down.
Fuel accumulator is a device designed to maintain the pressure... it is
located by the fuel pump and fuel filter. Over time and age, this device
develops a pinhole and leaks pressure out.