SL sometimes takes along time to start

[944s2c]

Hello, maybe some one can provide some guidance on a problem I'm having with my 1991 300SL...after driving to work,upon return to the car 9 hours later, it takes an unusual amount of cranking to get it to fire up.Turns over normal,just takes more cranking (10-15 seconds) than it should. The rest of the time it fires right up.Is there a fuel accumulator or possibly a check valve in this system? thanks for the help,Dan