P220g Onan engine problem

stevem5215 · Feb 25, 2009

I have a Steiner with a P220G spec d engine. It's missing on one cylinder when under a light load. If i take the load off of the engine the cylinder comes back. Not sure which one it is. I tried the spark plugs so far. And put some ISO into the gas. Fuel filter is clean and it only has 600hrs on the engine so it's not been heavily used. Any suggestions ?

Steve

Stimw · Feb 26, 2009

Common problems-
Valve sticking
foreign object in intake interupting valve operation
Ignition problem- points or condenser
bad spark plug or wire ( Champions are the worst, had new ones bad)
exhaust restriction- two into one, too small

oldmech · Feb 26, 2009

Hi! 1 Take compression if you can. 2 May be carburator . try to unscrew Hi-speed jet screw 1/8 turn. 3 Drain clean and adjust carburator. 4 Drain fuel tank Fill with NEW GAZ and check for good supply to carb. 5 Check for a Good, a long Blue spark. I think you have a minor trouble! Good Luck! Oldmech

jcmseven · Feb 27, 2009

I have nothing to add to the opinions, but would say this has been an experience I have had with two Onan's in the past. One was traced to the sparkplug being fouled and one never was discovered. My power equipment dealer at the time said this was the reason he was never an Onan fan. They were expensive engines, though as I recall.

John M

stevem5215 · Feb 27, 2009

Well, I figured it out. I had ordered some ignition parts from onanparts.com and they came today so I set out to put them on. I got the plugs and wires on it and went to crank it and nothing. Nothing was happening. Cranked it for a bit more and tried some either on it. Nothing. Could smell the gas and either though. I pulled one plug wire off and set one of the old spark plugs on the shield next to ground and tried it again. It was sparking ! And suddenly it kicked like it wanted to run (on one cyl). I shut it off and put the plug back in and it fired up. Hmm... So then I tried it again with it on the new wire and same ole' thing. No kick. Turned over but wouldn't fire. Took that plug wire off and tried the old one. Same thing. hmm.... well, as it went along I tried cleaning and checking the wires at the coil. Nothing helped. Except I figured out that when I "wiggled" the wires going into the connector near the coil and regulator that suddenly it wanted to fire. Ahha ! loose connection ! And this is a result of a connector built in 1994. It was loose. I took the connection out of the connector and cleaned and "tightened" them with a needle nose and sure enough no more intermittents. It's fixed. Amazing huh ? And it could only happen to a guy who's a electronic tech. I even had gone as far as putting my oscilloscope on the wiring to see the waveforms from the spark plugs. Everything looked pretty normal at the time cause it wasn't misfiring. But this connection thing is probably pretty common on this engine setup just because 15 year old connectors just don't work as well as newer ones.

Steve

Fordlords · Feb 28, 2009

I have not heard of anyone who wasn't an Onan fan

Their ignitions can be quirky, but not at all an uncommon problem on ANY older small engine, and something you have to expect. Mechanically, the Onan Performers are about as good as an air cooled small engine can get. Onan got the horizontally opposed twin mechanically perfected where it seemed like no other small engine maker really could- I think they beat the pants off of Kohler's cast iron cylinder K's and Magnums. When you listen to a good Onan twin running, they are music.

Good catch on that problem Steve. It's seen too much today where mechanics are just replace parts happy, not really troubleshooting the problem. They just want to replace parts until the problem goes away, when in the majority of cases the problem is something really simple to fix, maybe only taking some time to diagnose it.

-Fordlords-

jcmseven · Feb 28, 2009

Martin,

I think you make a good point. When I bought power equipment many years ago, the Onan was considered the Cadillac of the air cooled engines. The Onan equipped machines were always more expensive. My local dealer for Gravely equipment, who sold and serviced literally thousands of tractors with these engines had a different view. He said from the service perspective either you had a good one or not. If it was good, one would get thousands of hours of good service out of it, and if not one would be in the shop the entire time he/she owned the machine. My physical viewing of his shop over the years echoed this statement. Despite selling about an equal number of Kohler and Briggs powered tractors, the Onan equipped ones were the vast majority of those in for engine related service. Despite this fact, I bought a total of three Onan equipped Gravely's and got good service engine wise from one of them. In spite of this fact, I liked the Onan and they do sound better than any other make to my ear. I also thought they made more power. The reliability, though, was seemingly hit or miss from unit to unit. I feel this was why Gravely phased out Onan over the years in its machines.

John M