P220 Running on One Cylinder

[GH720 0]

I have the P220 in a grasshopper mower.  It is around 1992.  I'm hoping to lean on you folks for troubleshooting advise.

 

Lately, the motor has been starting hard.  When it does start, it's hard to get it revved up to full throttle.  Sounds like it is running on one cylinder.  It surges as well.  Today, it didn't have enough power to mow.  I checked spark, and I wasn't happy with the spark on one cylinder.  It was pretty weak.  Didn't seem to matter which side of the coil the plug wire was hooked to or which spark plug.  So I concluded it was a plug wire.  I replaced the plug wire, and plugs, and now I'm happy with the spark on both cylinders. It still wasn't running good, so I tore the carb apart and cleaned it and blew out all the passages.  After the carb tear down, I wasn't able to get it running.  Figured that maybe the float bowl is empty, so I poured fuel down the carb.  It fired up for a few seconds, but the same as before it is running rough.  Now it won't run continuously, so I may not have the carb set quite right, but I think the only setting I would have changed was idle.  Check and plugs and both have good spark.  One is black, but the other is clean as it was when I bought it.  I put the dirty plug in, and left the clean plug out.  Adding a bit of fuel to the carb, I managed to run it on one cylinder for a few seconds.  I then put the clean plug in, and pulled the dirty plug.  I was not able to run it on that cylinder. Figured maybe I had a bad plug, so I pulled the clean plug, and then put the dirty plug in it's hole along with it's plug wire.  Added a bit of fuel to the throat of the carb, and cranked it.  That cylinder won't fire. 

 

I'm trying to think of next steps.  Perhaps a compression test on the cylinder that won't fire?  I know it's got spark.  I'm pretty certain it's getting fuel if I pour fuel down the carb.  To completely rule it out, I've thought of getting a syringe and squirting fuel directly in that cylinder, installing the sparkplug and then crank it over. 

 

Other thoughts/ideas appreciated.  If this is a mechanical issue, what is the most likely problem?  Valves?

[djohn24 10]

GH720, Not a expert here but, I have a  520H and I have learned a lot from this site on the Onans'. It sounds like you may have a loose valve seat issue. I'm guessing a compression test is going to be low on the cylinder that isn't firing. Not going to be much help in finding the exact cause. You would be better off doing a leak down test on that cylinder or just remove the head on the non firing cylinder and rotate the flywheel and check for a loose valve seat. Sure some of the experts will jump in here once they read your post. Good Luck!

[lynnmor 6,778]

9 hours ago, djohn24 said:

GH720, Not a expert here but, I have a  520H and I have learned a lot from this site on the Onans'. It sounds like you may have a loose valve seat issue. I'm guessing a compression test is going to be low on the cylinder that isn't firing. Not going to be much help in finding the exact cause. You would be better off doing a leak down test on that cylinder or just remove the head on the non firing cylinder and rotate the flywheel and check for a loose valve seat. Sure some of the experts will jump in here once they read your post. Good Luck!

Good post, always check the compression first thing.  Your doctor checks your vitals first to see if he has anything to work with.

[GH720 0]

Thank you.  I will check the compression.  I'm not going to report back for a bit though as I've had some other stuff come up that I need to deal with first.  I appreciate the help!

[GH720 0]

The right cylinder (when looking at the drive shaft), has 105 psi compression.  The left cylinder has perhaps 5 psi.  I'm at roughly 3300 foot elevation.

 

Is there any chance the fix could be as simple as a valve adjustment?  I will google to see if I can find information on how to do this.  Is there anything else I should be checking?  What is the most likely issue based on your experience?

 

Thank you  

 

[djohn24 10]

GH720, my guess is that, valve adjustment isn't going to correct your 5psi reading in the left cylinder. With that 5psi reading, it leads me to think as I mentioned before. A loose valve seat. I doubt bad rings or worn cylinder would give that low of a reading. Again, not an expert here, just trying to help. I say a leak down test would be your next step Or, remove the head on that left cylinder and inspect the valve seat. Here is a link of a Onan valve adjustment. 

 

[GH720 0]

I finally pulled the valve adjustment cover.  There is a build up of something (carbon?) on the intake valve shaft on the low compression cylinder.  I thought that was odd because the other cylinder was clean.  I then pulled the head off the engine and found the intake valve seat is lose.  I calipered the OD of the valve seat, and it is 1.566".  I went to onanparts.com.  They sell oversized valve seats with an OD of 1.562".  So I'm guessing this engine has had the valve seat repaired once before (I bought it used, so I don't know the history).  I've asked onanparts if they have a larger OD valve seat, but I'm guessing not.

 

So my next question is what are my repair options if there aren't larger OD valve seats available to press in?  Is it possible to build up the aluminum, and then cut another hole?  Or am I further ahead finding another motor to repower it with?  IF there aren't any options, perhaps I try and loctite it in, and peen all around the seat with a punch in hopes that it might hold?  

 

 

[djohn24 10]

GH720,  If you have a machine shop around you, they might be able to fix it.  Our local napa machine can fix them. Here is a post of a member I know that, has had them repaired there.

Posted April 28 · Report post

i can get an onan valve seat fixed at a local napa machine shop for about $ 100.00. i pull the motor and strip it down to the bare block. take it to the shop and they order a new valve seat and machine it down to fit the blaok and install. i have several motors that have been repaired. if you want to get rid of your onan's in favor of replacement, i'm always looking for bad motors for a good price lol, depending where you are in Delaware i'm not too far away

 

 

 

 

eric j     

[GH720 0]

Thank you djohn24.  I would like to pursue a repair (much cheaper). But I'm curious how many times this can be done.  Based on the measurements of the valve insert, I think this valve has been done once already. Are there valves available that are larger than 1.566"?  I haven't found any yet.....

 

 

 

[djohn24 10]

I do not know if there are any larger. I don't  think your  going to find a cheaper fix then the one I mentioned. To install a larger seat, your going to have to have some machining done. And to try and peen and use loctite in my opinion, would be a short temporary fix. If at all. I see your from Canada. Not sure how $100 American dollars compares to Canadian money. But, that isn't a bad price to have your Onan fixed and up and running like it should.

[djohn24 10]

GH720, You can check with the "ONAN GUY"   boomers_influence  a member on here any many other forums. Thought I would have seen him jump in here and give some input. He could tell you if they have bigger valve seats or give you avice on what to do.

[GH720 0]

Thank you.  I will see if I can figure out how to PM boomers_influence.  I agree, if there is a way to put a new valve seat in, that will be the cheapest option as the only other option I'm aware of is to repower it.  Smallenginewarehouse has a repower kit for my mower that is $1700 US.  

[djohn24 10]

Your welcome! Yes, my father purchased a engine from them to repower a 918H agco allis tractor. around $1400 for their 18hp. It dropped right in and hooked up just like the old one. He had a Kohler Triad TH18 engine. It lasted 12 years and started using oil really bad.  Could no longer get any engine parts for it! He faithfully maintained it every year. From what I learned, the Triad was not a very good engine that Kohler produced. Anyway, you could also look for a used Onan engine on craigslist or ebay?

[GH720 0]

I contacted Boomers_influence.  He is a wealth of knowledge.  I wish he lived next door!  The main thing I learned is that any machine shop that does this type of work has access to thousands of valve seats sizes and the machine shop will be the only folks that know if this engine is repairable.  He indicated there was a good chance this may not be repairable given how large the existing seat is.  

 

Today, I managed to locate a local shop that does this sort of work.  I'm thinking of tearing the engine down so I can take the block and get a quote/opinion.  

 

Questions:

1) I grew up on a farm, so I'm pretty handy.  However, I haven't opened up an engine for 30 years.  I'm wondering how complicated it is to tear this engine down myself?  

2) IF I tear this down myself, is there anything I should anticipate I will need to replace.  For example gaskets?  Head gaskets came off in good condition.  But that is all I know so far. I'm mainly trying to understand what this will cost me.  It's a pretty old machine to be sinking a lot of dollars into.

 

I suspect I will learn some answers to these questions when I look for some Onan tear downs on the net.

Edited August 25, 2016 by GH720

[djohn24 10]

Well, I'll try and tell you what I know. Tear down is pretty straight forward. How much you need to tear down to have a valve seat replaced? I'm not sure. I guess you can leave the pistons , rods and crank in. If not, the hardest part would be to remove the crank gear off the crank. Which you will find once you remove the timing cover. There are several videos on youtubeshowing how to do it. I would replace any gaskets that you come in contact with. A complete gasket kit is $189 on onan parts. You may find a better price with Boomer? I had a P216 gone over at the Napa shop. I think my bill to have the cylinders honed, crank removed an polished, all parts checked to see with in specs, rod bearings crank journals , cylinder walls,cam and crankshaft end play.They reinstalled  crank and crank gear. I provided the gaskets. To start, I would go back to Boomer and ask how much needs to be tore down to have the valve seat checked/replaced. If you are not concerned with the rest of the engine and just want to get that fixed to keep cost down...That's going to be your cheapest route. And might be all you need to get more years out of it.

Edited August 26, 2016 by djohn24
Oh, bill at napa was $380

[GH720 0]

Thank you for the information.  I found a local shop that can do the work.  They looked at it and said there is not enough material left to cut and seat another seat.  They said they would have to build it up with welding.  After they are done that, they would cut the intake seat.  The heat from welding, will wreck the exhaust seat.  So they would have to do that one too.  Then they would have to hone the cylinders.  Because of the unknowns with this, it would be a straight time job.  Maybe $150 to 250 US, but no guarantees.  As well, they want it completely tore down (cylinders out, valves out, etc).  IF I have to tear it completely down, are there other parts I should buy, like rings?

 

Boomer and I had discussed welding....he told me there is no way to make a perfect weld on a block that has been exposed to oil/gas.  

 

If I'm adding everything up correctly, I might be able to get this motor working for 1/4 to 1/3 the cost of repowering.  And the repair could last a few months to 20 years. 

 

 

 

 

 

 

 

[woodchuckfarmer 333]

I had 2 intake seats done. I just removed the heads valves and flywheel. all the tins muffler and intake manifold. the guy charged me $130 for the job             Wayne

[GH720 0]

Thank you, I think the welding is driving the cost.....plus everything costs more north of the border!