Liberty work shop 9 #1 Posted September 1, 2022 The Onan on my 520h does this " surging thing " from time to time . Anybody have any thoughts on how to fix it ?? Thanks , Jerry ... Share this post Link to post Share on other sites
daveoman1966 3,745 #2 Posted September 1, 2022 I had similar issue with Onan P220. Problem source was the intake manifold gasket at the rear cylinder. Replaced the gasket...no more issue. 2 Share this post Link to post Share on other sites
Ed Kennell 38,048 #3 Posted September 1, 2022 Clean the carb, clean the carb, clean the carb. 1 Share this post Link to post Share on other sites
DougC 2,641 #4 Posted September 1, 2022 Yeah. Carb needs cleaned. Fresh non ethanol gas used from this day on........ 1 Share this post Link to post Share on other sites
Rick3478 428 #5 Posted September 2, 2022 Governor stability tends to be marginal on the Onans. Anything that leans the mix makes it worse. Vacuum leak, varnished jet, low float level, etc. Share this post Link to post Share on other sites
Liberty work shop 9 #6 Posted September 2, 2022 Many thanks for taking the time to reply ... I would never have thought it was running lean when it misbehaves like this because according to the exhaust , it's running rich ... Having said that , I will further explore the carb and intake gasket theory ... Thanks again and will let you know how I progress ... Jerry 1 Share this post Link to post Share on other sites
Snoopy11 5,714 #7 Posted September 2, 2022 If you post this in the engine section... more engine gurus would see it... Don Share this post Link to post Share on other sites
NA73 70 #8 Posted September 8, 2022 I may be a little late to the party, but the 520h had a surging and it turned out to be the intake gasket. sprayed starting fluid around intake to see if idle changed. also, if you chop the down runners(? not sure the actual technical name) - you'll see what I mean if/when you get the intake manifold out - you can install the new intake gaskets without having to remove the exhaust manifold. Share this post Link to post Share on other sites
