Onan 16 not running well

[PMaine 31]

I have an Onan 16 on my 516-H that out of the blue started running badly.

 

I ran the engine for an hour doing work around the yard and suddenly it started surging and acting like it was out of fuel. I made it back to the garage and shut it down to add fuel, but it had at least half a tank.

 

Using the choke doesn't improve running, I just get black smoke if I advance it too far and it bogs down even more.

 

No leaks anywhere that I can see.

 

I pulled the spark plug wires off the clyinders one at a time to see if I had a dead one but the results were the same on both for what thats worth.

 

With it running I hunted around all the wiring and nothing changed, all wiring looks good.

 

Where should I start? Thank you!

Edited April 14, 2014 by PMaine

[Ed Kennell 35,848]

Clean the carb.

[nylyon-(Admin) 7,121]

I would start with the carb as well.  There's a plug at the bottom of the float bowl which you can remove and gain access to the main jet.  Spray some cleaner in there getting the jet as best you can.  

[PMaine 31]

My understanding is that the carb on this motor is touchy? Are there any gaskets, or anything else I will need if I do a tear down?

 

Thank you!

[Joefrommi65 18]

This is a post I followed when my 416 started acting up

Hope it helps

Edited April 14, 2014 by Joefrommi65

[danjmah 71]

Here's the post that helped me tremendously when my onan was surging:

 

[the_nite_owl 15]

The 16HP Onan on my D-160 was doing essentially the same thing.

Does your carb have the brass or the fiber float?  If it is fiber the float could be swollen from absorbing ethanol in the fuel and getting stuck whenever the level of fuel in the carb changes like if you take off or stop quickly or drive on a slope.  Mine would run fine until I did one of those things then the float would stick and she would stutter and stall.  I finally replaced the float with a brass one I got on eBay.  I spent last evening trying to get just the right adjustment for the float in the carb and when I finally did she ran fine without any trouble.

You want to make certain there are no air leaks at the gaskets for the carb as well or she may not pull fuel in properly. 

Does your engine use an integrated fuel pump on the carb or an external fuel pump?  Either way you need to make certain that the vacuum line is not leaking so that the pump will work properly but if you have an external mounted pump you can take off the fuel line leading to the carb to see if it pumps fuel while you are cranking the engine.

 

Black smoke could indicate the engine is running rich and you are getting too much fuel and not enough air.

[Desko 552]

The nite owl the old model DD carbs on the b43 and bf-ms carbs are like that but the new performer engines have different carbs without the fiber floats and don't have brass floats but Nylon from what I'm aware of.

[PMaine 31]

Thanks for all the feedback. The weird thing is it runs great and then all of a sudden it starts to act up. I have not been into the carb yet, too many other projects going.

[PMaine 31]