Kohler 7.5 EKD not running well

[nhuyck]

I have a Kohler 7.5 EKD marine genset that continues to shut off and puts the code "check engine" on the screen. The manual says:

Check the following:
Fuel supply
High fuel restrictions
Air leak in the supply side of the fuel system
Inoperative low or high pressure fuel pump
Fuel vaporization in higher than maximum temperature
operation specifications

Tests I have conducted:
Fuel pressure at Schroeder valve: 52-54 psi (Supposed to read 42 psi)
Changed fuel filter
Checked all fuel connections for leaks or air

Anywhere else I could start? It has no return line, so there is not a restriction in there that would cause high fuel pressure. Nobody in my area works on generators and the closest dealer is 5 hours away by car (and nobody calls back anyway).