Onan P224 Coil ?

[KILROY]

Jeff,
With the engine running check the head gaskets for a leak. After you cut the cedar pull the head off from the lowest cylinder. It is usually fouled the worst. Check for carbon build up and if the valves are seating properly.

[Gary_C]

Jeff

I have a lot of problems with fouled plugs on older gas engines. Just  replace them when they get black and sooty like that.

Don't be surprised if you do have a valve problem. This gasoline has so little lubricating value that sometimes the valves will stick even when just rebuilt. I have had valves stick only after the engine was warmed up and it can happen at idle or at higher speed. On an engine with some hours of running, the valves can stick because of deposits on the valve stem. As the engine warms up the clearances in the valve guides can close up and some valves will stick.

Hope it's something else, but don't overlook that possiability.

[Buzz-sawyer]

Your description of the engine running fine for an hour then cutting off like you hit the kill switch is a CLASSIC sign of electrical failure.
It could be a valve issue.....(heating up and expanding)....I would adjust them first any way.
A coil heats with the engine then expands and will cut out at times ....I have encountered this 4-5 times myself.
Your plugs look awful sooty for one hour........have you cleaned the points and taken a good look at them?
I have also seen points with oxidation on them cause similair symptoms... ;)

[KILROY]

Engine has electronic ignition. No points. Some of the older engines have points. I have an 18 horse Onan on my lawn mower with points. Need to check every once and awhile.

[Fla._Deadheader]

  I youster have one a dem Onanns. Had it on a wood splitter I built. After settin for a few months, both exhaust valves would get real sticky. Had to pull both heads and lube 'em.

 Marvel Mystery Oil gits 'er done. !!  :D :D

Drizzle a little down the carb while you run the engine. It will choke down, but, don't let it stall. A little dab-l do ya.  ;D ;D

Might wanna run a hotter plug than whats in it. I've heard about burning pistons doing that, but, 40 years and I haven't burned one yet.  ;) ;)

[Jeff]

I gotta think the sooted up plugs were from the 1/2 hour we ran the mill when it was running so bad, trying to get through a log.

ITS HOT HERE!  Tammy and I just sawed up that cedar with no sign of the engine running crappy as it did the last two times we ran it.  Its time to go stick my head in the pool.

[KILROY]

 Jeff,
Way to go big guy! That is the kind of repairs I like. Cheap! Just a dirty carburetor.

[exfarmer]

I realize that this is an old thread and you have probably solved your problem by now, but I thought I'd get my two cents in hoping that it helps someone. I found this post when I googled Onan valve adjustment. I had the same problems that you discribed, Jeff. I had tried every thing! New ignition pickup (over $100), different coils, new plugs & wires. Nothing helped, as soon as it warmed up one cylinder would start missing badly. Next I cleaned the carb (not very dirty) and checked for leaks in the intake. When I had the intake manifold off I checked the valve lash and discovered that there was zero lash on the intake valve of the cylinder that was cutting out! I couldn't find out what the lash should be so I set all the valves at .013. Problem solved although I think the lash should be tighter as now you can hear the lifters ticking. Anyone know what the setting should be?
     Here are some things that I discovered while trying to solve my problem that I hope will be of use to others with Onan engines.
- Ignition pick up module (behind flywheel) can be tested with an ordinairy test light; connect the test lead to the black wire coming from the pickup, with the key on rotate the engine by hand, if the coil is good the light will turn of & on. If you crank the engine with the starter the light should flicker.
- Instead of buying a new, very expensive Onan coil I tried using two Delco coils, one per cylinder. They seem to work fine and produce a good strong spark. 

[tnlogger]

exfarmer welcome to the best forum on the web good post  8)

[jpgreen]

I LIKE that Delco coil idea.. !   8)

[doug]

I realize that this is an old thread and you have probably solved your problem by now, but I thought I'd get my two cents in hoping that it helps someone. I found this post when I googled Onan valve adjustment. I had the same problems that you discribed, Jeff. I had tried every thing! New ignition pickup (over $100), different coils, new plugs & wires. Nothing helped, as soon as it warmed up one cylinder would start missing badly. Next I cleaned the carb (not very dirty) and checked for leaks in the intake. When I had the intake manifold off I checked the valve lash and discovered that there was zero lash on the intake valve of the cylinder that was cutting out! I couldn't find out what the lash should be so I set all the valves at .013. Problem solved although I think the lash should be tighter as now you can hear the lifters ticking. Anyone know what the setting should be?
     Here are some things that I discovered while trying to solve my problem that I hope will be of use to others with Onan engines.
- Ignition pick up module (behind flywheel) can be tested with an ordinairy test light; connect the test lead to the black wire coming from the pickup, with the key on rotate the engine by hand, if the coil is good the light will turn of & on. If you crank the engine with the starter the light should flicker.
- Instead of buying a new, very expensive Onan coil I tried using two Delco coils, one per cylinder. They seem to work fine and produce a good strong spark. 

Thanks for a timely post.  I am having the same problem except this engine is on a Toro zero turn mower.  I connected a pass thru neon tester to the spark plug and could see the spark cutting out and then flickering on (immediate backfire).  Once while cranking the engine, I saw no spark at all for about 50 cranks and then suddenly, it was there and the mower started fine.  I have already replaced the coil (the original tested marginal) and condenser and plugs and cleaned out the carburator.  The electronic module behind the flywheel is so difficult to access (I have to remove the engine from the frame and disconnect hydraulic pumps, etc, that I left that off of the repair so far.  By the way, I have the Onan Engine Service Manual for the P216,  P218, P220, and P224 engines.  On the p224, the intake valve clearance (stem to guide) is 0.0010 min and 0.0025 max.  On the exhaust, the values are 0.0025 min and 0.0040 max. 

The manual calls out this procedure to test the electronic control module:  Connect positive volt meter lead to negative (larger diameter terminal) of coil.  Then connect negative lead of volt meter to ground.  Turn the key on and rotate the flywheel slowly by hand (remove spark plugs first).  Voltage should switch between battery voltage and 1 - 1.5 volts for each revolution.  If it does not switch properly, replace the module.  Is the electronic control module an always bad or always good sensor or can it act intermittently?  

The only other electronic circuit item that could kill the spark appears to be the oil pressure sensor.  According to my wiring diagram, if oil pressure sensor (normally open) closes, it grounds out the ignition circuit.  Is it possible that the sensor is malfunctioning or fluttering?  The service manual says to connect a jumper form positive battery terminal to positive coil terminal (smaller diameter terminal post).  If spark occurs when cranking the engine but not otherwise, then problem is low pressure cut out switch or true low pressure in the oil system.  If no spark occurs then the ignition module should be checked as noted above. 

I also noted that the head gasket is leaking (bubbles when running).  I should replace that and will do so unless the backfiring is damaging the head gasket.  If that is the case, then I will need to solve that issue first.  Any suggestions are welcome..........Doug

[Minnesota_boy]

Yes the electronic control module can be intermittent.  I had one that way on  a pickup truck.  It tried to get me to walk a few times before I replaced it.  Mine would open circuit when it got hot, usually on my way home after a long day (warm weather) when I didn't really want to walk.  Open the hood for a few minutes and relax, it would fire up and take me the rest of the way home.

[jpgreen]

Good info there Doug.

Hey- what's the valve specs on the P216, and if you don't mind what do they show for the adjustment proceedure?

AND welcome to SawDust Heaven..!  8)

[VA-Sawyer]

Note:  I have solved this problem, but the answer came from waaaayyyy out in left field. I will post the problem and my troubleshooting results in this post. I'll give you all a couple of days to try and figure it out, then I will post the answer.  Believe me..... the solution will knock your socks off.  The only member on this board I think might figure this one out is Sparks,  and only because he may have experienced it before.

I got one for all you troubleshooters.... Last Thursday my engine started really running like cr@p when sawing. It sounded like the coil was breaking down and losing spark. It would throw a white cloud of unburnt fuel out the exhaust and make noise like someone was banging on it with a hammer. As soon as I stopped the foward travel the engine ran fine again. To be honest it was a scary thing to experience.
I changed the fuel....same problem.  I checked the compression, 125 psi cranking the starter with the throttle open, 90 psi cranking with the throttle closed. Left and right cylinders match pressure within a few psi. My maintenance logs confirm the numbers to be normal. There is metallic spatter buildup on the spark plugs, indicating either pre-ignition or heavy detonation. That agrees with the  scary hammer like noises I heard while sawing. I have an inspection light for looking in cylinders through the spark plug hole. It doesn't show any damage to the valves, pistons or cylinders.  The engine turns over smoothly by hand and the oil doesn't show any metalflake. Ignition timing is found to be good.  Mechanically, the engine is in proper shape.
After cleaning the junk off the plugs and putting everything back together again, I fire it up. It does start easier and idle smoother, but that isn't any suprise considering the condition of the plugs.
While it is running at idle , I put the FWD/REV switch in FWD and the engine develops a rough idle as soon as I start to move the head. I put it in REV and the idle is smooth. I raise and lower the head to see if it has any effect on the smoothness of the idle...no effect, other than a slight drop in idle speed due to the altenator loading up from the electrical load. The slight RPM drop during an electrical load is normal, but the roughness when I drop it in FWD is not. A little more checking shows me than I can make it run even rougher if I try to hold the head from moving in the FWD direction. Doing the same thing in REV does not cause it to run rough. I turn on everything electrical I can...debarker, lights, run the head UP and Down....engines stays smooth. Put it in FWD with minimum electrical load and start moving the speed knob...engine goes rough.
One last bit of info... the FWD/REV runs the head back and forth just fine when the engine is off.


You now have all the info that I had when the light bulb in my head lit up.
Good Luck,
VA-Sawyer

[scsmith42]

Doug - Exfarmer - Great posts and welcome to the forum!

Doug - does your manual show a specification for "valve lash" - ie the clearance between the valve stem and the rocker arm?  JPGreen - I believe that the valve "lash" is the spec that you're looking for - not the stem to guide clearance.

The valve stem to guide clearlance is typically only referenced on a rebuild, and it represents the wear that occurs on the valve stem and guide.  The only way to change the stem to guide clearance is to replace the guides, valves, knurl the guides or install some type of guide insert.

Excessive stem to guide clearnance will result in increased oil consumption, and reduced compression.  Way excessive clearnance can lead to a dropped valve (broken valve head - very bad!).

Scott

[ARKANSAWYER]

  VA-Sawyer   Drum switch is bad.

[VA-Sawyer]

Sorry, Arky...Not the Drum Switch, but at least you are thinking far enough outside the box to possibly get it.
The FWD/REV system works ok. There is no chain binding, no problem with the belts or pulleys, and it seems to be traveling at normal speed in full foward or reverse. The ampmeter shows normal draw.
The main symptom is the ignition seems to break down when the FWD/REV switch is in FWD and seems to get worse as the feed motor needs more power.
VA-Sawyer

[amberwood]

coming in at a late stage here but this sounds very much like the voltage is dropping too low for the coil as the extra load is applied. Battery conditon? Alternator output?

DTR

[VA-Sawyer]

DTR,

That was one of my first thoughts, but pulling the heavist electrical load I could, debarker, lights, up/down motor raising the head etc, did not cause a rough idle.  A voltmeter on the + terminal of the coil shows better than 12 volts DC even while the idle gets rough when putting it in FWD.

VA-Sawyer

[jpgreen]

Something is grounding out intermittently when you go in forward feed.

What is it?

[jpgreen]

Bad keyswitch.

[jpgreen]

Does the problem happen only when the debarker is on?, or when it's off as well?

[VA-Sawyer]

Debarker has no effect on the problem. 

I suspected the keyswitch at one point. As I noted in my previous post, 12V DC at the coil + terminal doesn't change with the problem.

[sparks]

If this mill was built between 1992 and 1995 and it has the original power feed circuit board you could be shuting down the ignition system. The old style board would have one of the caps go bad which caused the board to bleed off current effecting the coil. As you increase the potentiometer the engine would begin to missfire. You would not see it in reverse because it is not controlled by the board.   Thanks

[VA-Sawyer]

Sparks,
Excellent !  Actually the mill is an '88 and I don't know if the board is original. I reached a point in the troubleshooting where I was convinced the power feed circuit board was causing the problem. I put my voltmeter back on the + terminal of the coil only this time I had it set on AC volts. With the engine not running and the key switch in the on position, I would get almost 2 volts of AC feedback when I put the FWD/REV switch in FWD.  Opened the speed control and found a loose solder joint on a capacitor. Re soldered the joint and fixed the problem.


OK Folks, here is what was happening... Because of the loose solder joint the capacitor was unable to do its job of filtering the AC feedback. The electronic ignition system was seeing this AC voltage and was false triggering the coil. When the coil is firing sparks at random times, the engine doesn't run very well. Also, these improperly timed sparks would sometimes happen as the piston was going up on compression causing the detonation I could hear and see the results of on the plugs.
So, there you have it. A very sick running engine caused by a bad circuit board that isn't part of the engine and is in fact, located some 3 feet away from the engine.  Go Figure !
VA-Sawyer