No Start Ford LRG 425

Can’t get our 2006 Ford LRG425 (SN# 06VG56426) engine that is part of an Eaton 21kW backup generator system. Here are the particulars:

• Engine configured for LP gas. Verified shut-off valve opens properly and I see ½ PSI before entering the zero pressure LC-50 throttle body.
• Verified that thecarburator butterfly moves freely and operates correctly when the engine is cranking
• Did compression testing on cylinders – all around 130 PSI
• I see spark when I remove spark plug wire and test for spark

This system resides in cold weather (Illinois) and does have a heater. Engine temperature at the top of the block is 90-95 degrees.
Any help in further troubleshooting would be appreciated.

Thanks

No Start Ford LRG 425