520H Flamethrower....

[Sierra51 4]

I originally posted this engine problem on MyTractorForum....and after reading some of the other posts there....y'all come highly reccommended for particular Onan quirks....so here it is....

 

 

Been away awhile....but had to jump right back on here to ask another "new guy" question....I did the tune-up on the WH and proceeded to cut about an acre or two....tractor worked and ran great....cleaned it up, put it up and didn't use it for about a month....weather a bit colder at start up, so I wasn't surprised when it took a minute to fire up....ran rough as it warmed up, then smoothed out as the engine came up to temp....fairly smooth....ran it around to the back of the barn to cut about a half acre....grass now dry and light brown....bumped up the throttle on the Onan, engaged the blades, lowered the deck and slid the trans lever forward just a bit....everything still running "smoothly" although the engine seems to have a minor miss to it....went about 30' and had about a 2' fireball shoot out of the muffler....shut it down immediately, opened the cowl, and after letting it cool down checked visually for fuel leak somewhere and smelled for that "excessive raw gas smell"....but nothing....is there something that would cause the fireball....and it was impressive....to come out of the muffler like that?....haven't run her since....looking to mount a fire extinguisher on her now....thanks, Paul

[smoreau 658]

sounds like you were only running on one cylinder.

[WH nut 553]

Running on 1 cylinder and then she lite off the raw gas. Fire it up and make sure its running on 2.

[Sierra51 4]

The one cylinder running makes sense....I'll check on that in the am....hopefully it turns out to be a loose plug wire....cylinder fills with raw fuel while no spark, then wire makes contact with plug....and boom, we have ignition of the fuel....alot of fuel....thanks, I'll get back with what I find in the morning....Paul

[Save Old Iron 1,563]

the dead cylinder is pumping unburned air fuel mixture into a hot muffler

when the fuel concentration in the muffler becomes able to support ignition - boom

[RMCIII 838]

Here is my  . You just invented "igniters" for a WH.... Let us know what you did so we can replicate the same scenario with ours...  I'm thinking of doing it the old fashion way, drill a hole into the exhaust manifold large enough for spark plug. Then run a gas line up to the plug/hole. Make sure you put an, on/off spigot, in line with the gas. Wire a lead to the battery, then back to a toggle. on/off switch. Increase RPM's, turn on the spark, and open the spigot of fuel. Wha-la.... Instant flames.... But you seem to have mastered it without all the unnecessary additions....  DO TELL..... I know, being a smart a***..... But I could not help it... Hope you figure out what the issue is...

 

Rob

[boovuc 1,090]

An Onan P series engine running "possibly" on one cyl. could indicate a bad valve seat which is a common issue with the Onan in a Wheelhorse configuration.

One could hope that it is as simple as a plug wire or a fouled plug.

It is a good explanation of why it shot flames. There are many here that have had their Onan's run on a single cylinder and didn't realize it right away. (You would notice it if you put it under load).

Let us know what you found and hopefully you can get to it before this crappy weather system turns to ice/snow up your way! 

[Sierra51 4]

I'm very familiar with tailpipe flamethrowers....lol....I just didn't expect it on my tractor....especially when it took it upon itself to do it without consulting me....I can also be somewhat of a smarta$$....my years in the military and law enforcement helped nuture that.... ....I did just happen to come inside to get the key after looking to see if the plug wires were loose....but both appear to be snug and making contact at both ends....so I'm not sure what would have caused the one plug not to fire and load up the cylinder with fuel....so any ideas would be greatly appreciated....if for nothing else it will keep my other half from ragging on me about buying a twentyfive year old tractor.... ....I'm new to small engines and the components particular to them....it ran great after the initial tuneup/service i did after I got it home from the PO's place....I really need to get a factory service manual.... ....thanks again, Paul

[Sierra51 4]

Great....is this an expensive repair on these engines since they aren't produced anymore?....

[AMC RULES 36,945]

Humm...let's put it this way.    

Probably won't be something you'll want to give your other half to hold over your head.      

[HorseFixer 2,012]

 

I really need to get a factory service manual.... ....thanks again, Paul

 

Here Ya Go!       P.S. I Wouldn't mind the look of some flames shooting out the stack of my Snow Chucker at Night! 

 

http://www.wheelhorseforum.com/files/category/12-engine-manuals/?sort_order=ASC&sort_key=file_name&num=10&filter_key=all&st=50

 

Or Here

 

http://www.wheelhorseforum.com/files/category/12-engine-manuals/?sort_order=ASC&sort_key=file_name&num=10&filter_key=all&st=60

Edited December 6, 2013 by HorseFixer

[Sierra51 4]

Thanks for the heads-up on the manuals....well had a few things to do today, but I did manage to fire up the WH this morning....checked the plugs as I had said and they felt snug....cranked her up and ran smooth with no re-enactment of torching a bunker on Iwo Jima....throttled up and engaged the deck to put a load on it....no change in engine sound or any other strange occurance....lowered the deck and ran a test cut....nothing to report....the vac guage stays steady (relatively)....charging fine....the tach is inop so I don't where the actual rpms are at....need to replace that....I will be getting a couple of new plug wires just to be on the safe side....

[leeave96 487]

I would think if the engine is running only on one cylinder it would be very audible and the engine/tractor would vibrate like crazy.

 

Did you experience any of these symptoms?

[Sierra51 4]

I would think if the engine is running only on one cylinder it would be very audible and the engine/tractor would vibrate like crazy.

 

Did you experience any of these symptoms?

Nothing to write home about....the tractor seemed normal until the flamethrower fx....I shut it off immediately when it happened....

[boovuc 1,090]

What we like to refer to as an "isolated incident". If you can't reproduce the error or in this case, the flame...............this is a good thing!

When my KT Kohler decided to get a divorce and go single, it was easy to tell it was on a single cylinder when I was checking for loose wires and the one cylinder jug was cool to the touch. Oh and the plug was as fouled and black as one could imagine.

Lets hope that you can never reproduce that flame again!

[HorseFixer 2,012]

 

When my KT Kohler decided to get a divorce and go single, the plug was as fouled and black as one could imagine.

 

 

Which brings up another question??   If my plug got fouled   I wonder if MJ would divorce me? 

[boovuc 1,090]

 Wow!

Here's hoping your plug never fouls, Duke!

[motox25 36]

When I started the Onan in my 520 after years of sitting it started running on one cylinder then luckily the 2nd kicked in after a minute. Sounds like a very smooth running single cylinder engine but it doesn't have that distinct smooth running sound. You could pull a plug wire while running and see if the engine stalls or sounds different to determine if it's running on both cylinders.

[Dieselcowboy 210]

Check intake and exhaust gaskets. Hidden place not often thought of.