We need a little more info, model#, serial#, type of fuel. Some of the older units needed 11.5 - 12.5 in. w.c. with all fuels, depending on age it could be spec'd at 7.5 in. w.c. for natural gas and 12.5 in. w.c. for propane. I don't want to mislead you with incorrect spec's. The static fuel pressure will drop sharply and bounce with the intake pulse from each cylinder as the engine is cranking, as the engine begins to speed up the pressure will drop and recover within a second or so, it's difficult to diagnose anything from those readings. What we look for and what Generac spells out is a difference between static pressure and steady state running pressure, no more than 1 in. w.c. pressure drop. That will normally confirm that the fuel supply volume, pressure, regulators, and piping are correct.
Generac model# 044563, Serial#4308603 NG, 425 cfh gas meter, with 10 feet of 1" black pipe .