Mitey Mac onan surges?

[1816case]

my new to me Mitey Mac runs good other than tilt cylinder (s) leak down slow. I never really even started it until today to put in storage shed. It idled at mid range good. Choke almost in off position after couple minutes.. but by time I got it to the shed it would 'surge' at idle and mid-range. I really haven't no time to look into it yet but does 'surging' indicate most likely fuel delivery issue? One other question is it ever issue of the cold winter causing seals to leak down in tilt rams? just curious.

 

[cdmccul]

You say choke - so this is gasoline engine? Surging like that I'd assume governor possibly, but most likely carb is dirty... But I'm not super familiar with Onan engines.

 

[solo machine]

When I bought my 5C with a Tecumseh it has a fuel pump. No surging issues.
The leaking down, is probably the seals going bad. I'm going to order all new seals for mine.

 

[foton]

it could be a fuel delivery problem , also it could be just a simple spring that controls tension on the governor. see if you can find a exploded view of engine and make sure all the springs are there and tensioned in the right holes on governor arm . There should be info.out there somewhere telling how to do this adjustment. Onan is now owned by Cummins diesel. Check fuel flow, fuel filters and fuel pump too.

 

[LeoB]

Foton is correct. Your issue could be engine is starving for fuel due to dirty fuel filters. At idle, the clogged filter may be able to supply enough fuel for smooth operation, but at higher throttle, it can't. And he is right about the governor tension spring, it controls engine speed. When you increase or decrease engine RPM on an ONAN NHC used in the Hydra-Mac 8B, you are telling the governor to run the engine at a certain speed. The governor then controls the throttle plate. Attached are pages from an ONAN NHC service manual for the carb and the governor areas.

My NHC has an electric fuel pump and external filter feeding the carb. You might start by pulling the fuel line after the filter. On my unit, when I turn the key to the "run" position before I turn the engine to start it, the fuel pump runs. Assuming your unit is the same, check the fuel flow first. Then perhaps graduate to the governor. My two cents worth.

Leo B.

 

[LeoB]

I am sending a second message following up on my last message. I don't see the attachment that I thought I was connecting to my last post. I'll try again.