Vinnie 6 #1 Posted February 7 Just changed the spark plugs on my onan p216 and plugs are wet with oil. What is the best way to fix this. Engine does run a little rough. thanks. Share this post Link to post Share on other sites
Ed Kennell 38,598 #2 Posted February 7 Onan_16_18_20_24.pdf Perform the breather maintenance as directed in the above manual. 1 Share this post Link to post Share on other sites
lynnmor 7,352 #3 Posted February 7 Always start with a compression test, if the engine ain't healthy you need to do the repairs needed. 1 Share this post Link to post Share on other sites
Vinnie 6 #4 Posted February 7 I did the compression test both cylinders on a warm engine 120. I checked and cleaned the breather. Here is a picture of the oily spark plug. The plug closest to the steering wheel is clean. Share this post Link to post Share on other sites
Vinnie 6 #5 Posted February 7 These plugs are and I only ran the engine for 5 minutes. What do think is it ok or should I try to resolve it? Share this post Link to post Share on other sites
Ed Kennell 38,598 #6 Posted February 7 Try running it on one cylinder only. Note any differences in the front and rear. Leave both plugs in, just pull one wire at a time. Share this post Link to post Share on other sites
Vinnie 6 #7 Posted February 8 One thing I noticed it would not start when I I had the plug closest to the steering wheel running, and the front plug pulled off. It did run different between the two cylinders. Share this post Link to post Share on other sites
Ed Kennell 38,598 #8 Posted February 8 It should run equally on either cylinder. Just to confirm, The rear plug is clean and the front plug is oily, correct. And which plug wire was off when it would not start? Share this post Link to post Share on other sites
Vinnie 6 #9 Posted February 8 Thanks for your help by the way. The back plug is closest to the steering wheel. The back plug is not oily. The engine would not start when I only had the front plug connected, the front plug is the oily plug. I was able to start the engine with both plugs attached and while it was running, I pulled off the rear plug and the engine still ran on only the front plug being connect but but it would not start with only the front plug connected. Share this post Link to post Share on other sites
Ed Kennell 38,598 #10 Posted February 8 So, the front cylinder has a problem. With both having good 120psi compression, the valves and rings must be sealing, and the breather clean and working, I don't have an answer as to how the oil is getting sucked into the front cylinder only. Any ideas @lynnmor ? Share this post Link to post Share on other sites
squonk 41,291 #11 Posted February 8 Onan uses waste spark technology. Both plugs fire at the same time. If you pull a wire off it kills the other cylinder as well. If you pull the wire off and ground it the other cylinder will fire. I would check the valve seals on the oily cylinder. Share this post Link to post Share on other sites
lynnmor 7,352 #12 Posted February 8 I will toss out a few thoughts: Try swapping the spark plugs and see if the front cylinder comes to life. Replacing the spark plugs with new ones takes that out of the mix. The front spark plug wire may be bad or the coil may not be firing that wire. Check the coil with an ohm meter probing in each plug wire hole, the information is in the Onan Service Manual. A very bad valve guide will allow oil into the combustion chamber as well as a bad intake valve seal. A loose valve seat can show good compression till it is real bad, hopefully you don’t have that issue. A broken oil ring, but good compression rings, can cause high oil consumption.. If excessive oil is entering the combustion chamber it will be caused by a bad oil ring, a bad valve guide/seal or pressure buildup in the engine. After checking the above it is time to pull the front head, an easy job. Take photos and report back. Share this post Link to post Share on other sites
Vinnie 6 #13 Posted February 8 Thanks so much I will get in it. Share this post Link to post Share on other sites
Vinnie 6 #14 Posted February 10 I checked the coil with the old meter checked out to be good. The spark plugs are brand new. It does appear to be leaking oil somewhere maybe near the bearing plate gasket. I’m thinking I have to strip the engine from the tractor. What do you guys think is next good steps. Like you said before maybe decarbonize the engine and reset the valves. Kind of nervous about taking the engine off the tractor. Anyone have any good steps to do that? Share this post Link to post Share on other sites
lynnmor 7,352 #15 Posted February 11 Since the front cylinder appears to be the problem, it is a simple job to pull the front head. Even the rear head can be removed with the engine in place but it is easier if it is moved a bit. The hood comes off easily for better access. Whenever installing a head a new head gasket should be used and a torque wrench is needed. Share this post Link to post Share on other sites
Cee245 818 #16 Posted February 11 (edited) What brand spark plug? I had a champion recently fail out of the box. It even had what I thought was pretty good spark when checking... I put another on and motor ran! Both plugs out of same 10 piece bulk box. Even put the defective one back on to confirm... Maybe try switching plugs before buying? I wasted a lot of time on other tests etc before trying that. somewhere I read about it happening to others. Edited February 11 by Cee245 Info Share this post Link to post Share on other sites
Vinnie 6 #17 Posted February 11 Great ideas. Thanks guys. Did anyone see there is a nice 518 H for sale in Charlottesville, Virginia? Share this post Link to post Share on other sites
