WH 520H / P220 engine isues

[vt92 0]

Hello all,

My Onan P220 engine is not running right. It starts normally, but then begins to run rough after about 30 seconds. Choking it make is run worse.

The last time I used it, I let the gas run out, so I thought it might need a new fuel filter. I replaced the filter, but that did not help.

I noticed when I turned off the engine, I could hear what sounded like liquid boiling. I found a fair amout of gas in the bottom of the air cleaner housing,like it had bubbled out of the carb. Do these carbs have a float? I am wondering if the carb is getting flooded.

Thanks for any advice.

[CRE1992 135]

If you disconnect the choke linkage after taking off the air cleaner housing, and take the 4 screws out of the top of the carb, the float will be right under it. I don't believe this would be a carb problem though, it sounds like more or less like a valve adjustment issue to me... Just thoughts

[zieg72 209]

Check the compression of each cylinder, unfortunately the classic sign of a valve seat in the rear cylinder but I hope I am wrong... Good Luck

[vt92 0]

Thanks to all who posted replies.

i checked both cylinders, they both had about 120 PSI. Sounds good, right?

I double checked the rear cylinder after the engine was warmed up a bit. It was still around 110 PSI.

Any other suggestions?

The engine runs smooth as silk for about 1 minute and then it runs rougher and rougher til it quits.

I need to try to pull the plug wires individually and see if I can tell if one cylinder is not firing or if it is both. Since they fire at the same time, I guess it is unlikely to be an individual issue.

Thanks in advance for you help.

[vt92 0]

I took off the top of the carb and checked the float. No obvious issues. I cleaned it and put it back together. Ran good for about two minutes and then started sputtering and died.

Any suggestions??

[wh79d160 52]

Just a shot , but maybe the seat gasket (needle & seat) is leaking & flooding the carb. :woohoo:

[bigd 0]

sounds bad should just give me that headache actually i agree with the float needle and seat something is not letting it stop the fuel flow.

[vt92 0]

Thanks for the replies!

Know the part number for the seat gasket? I found a parts manual, but I don't see the gasket listed by itself. I do see kit# 146

[P3x 57]

I don't think the gasket is sold individually only as part of a kit. You try the folks at Onanparts.com, if it is available as an individual sale item they would most likely have it.

They have the kit you mention for 89.50 and a new carb for around 150.00. When I was tortured by surging I opted to purchase both. I was able to get the carb/engine running good without overhauling or replacing the carb but figure I'll need the spares in the future.

I clean my foam air filterand blow out the element frequently and spray gumout through the carb if I notice any stumbling or harder than normal starting. It seems the 520 carb is fairly sensitive to dirt/dust with the airbox area having a propensity to ingest/collect alot of dirt.

[vt92 0]

I took the carb off and cleaned it really good. I put it back on and now the engine runs fine! It looks like I am going to have to clean it once per year, since I've had to do the same for the past two years.

I wonder if I could add some type of pre-filter to the air intake tube? Maybe some coarse foam of some kind. It might be good to reduce the amount of dirt that gets into the air cleaner housing.

Anyone know how I would go about cleaning out the gas tank? Would I use carb cleaner or some other kind of solvent? I want to make sure there isn't any trash coming through the fuel line, even though I have a new fuel filter.

[SAM58 30]

I had a 1992 520H that had a simalar problem, it would run great for a few minutes and then start missing and quit. It ended up being the fuel screen on the shutoff valve in the gas tank. Little floaties would collect around the screen and shut off the gas, let it set or put more gas in it and it would run good for a little while...

:D