Yup... add me to the WW ONAN5500 shuts down for no apparent reason syndrome.
Starts like a champ, usually runs for maybe 2-5 hours, with 2 ac running full blast, then shuts down. Won't start and run again till it sits for at least a 1/2 to 1 hour. Then it will run for 45min to 1 hour or so. The longer I leave it off, the longer it will run on restart. When it runs, it runs perfectly. It typically dies after running for hours, usually right when we are ready to sit down for a nice dinner.
It has about 250 hours on it now. Got it with 24 hours, and its been doing the same thing ever since then.
Tried the remove gas cap vent test.
Changed the carb, with new Onan oem carb.
Changed all fuel filters.
Changed the $100 low pressure Onan fuel pump.
Checked the full length of fuel line, cut it open & checked it for deterioration or separation.
Did a full tune up/maintenance,air filter, plugs, valve adj, compression test, set voltage, checked hz.... a few oil changes with Mobil 1
Did the second fuel filter delete safety recall
Checked the oil pressure cut off switch.
Gave it a full load test, over 6000watts.
Seems to do it less or not at all(maybe), when the tank is completely full of fuel to the tippy top. It ran a full day of maybe 14+ hours till I turned it off. Usually I never have to turn it off... Which leads me to believe could be a tank fuel pickup problem. Unlikely, but its certainly possible. It sure seems fuel related to me.
Next step for me, is to try the gas can next to the th with a short fuel line direct to the carb, with fuel tank higher than the carb, for gravity/siphon fuel feed.
Can't seem to find any rhyme or reason for this problem as of yet, but I will... if its the last thing I do.
jmo
