I added 20 gallons to top it off last Friday and drove 200 miles. How much old, stale, fuel would the GENSET fuel pick up tube hold? I drained some, maybe a 1/2 cup. Varnish in the carb is a possibility. Can you clean the carb installed with any kind of spray cleaner? The model # is Onan 5.5HGJAB-1038C. I reconfirmed the error code and it's a 36 not a 37. 36 deals with gas, spark, air cleaner, all of which I have confirmed. I'll check out the two links you sent. If you come up with anything else let me know. Thanks!