M#0052420 13kw generac. Not starting on LP when fuel selector in LP position. Move selector to NG selection and unit starts and runs. After running, moving to LP will keep unit going. After warm-up, unit will start on LP in selected LP position. Gas installer has checked fuel supply and pressure and says it's ok at 11"WC. Spark plugs have been checked and replaced at 0.030". Generac tech service says to look for vacuum leak?
Skip Douglas SkipD
Was the gas pressure checked with the generator attempting to start or just with no gas flow (static pressure)?

Another way to test the pressure properly is with a controlled leak device to have the same flow that will be needed by the engine but without the engine turning over.
Skip Douglas
A vacuum leak is a good possibility. It could prevent the gas regulator from opening enough for starting on LP.