Case 448 Help

fran35

New User
Hello from PA, happy to join the forum. Seems like a very helpful place. I am hoping someone with more experience than I can help with my problems. My situation is:

I recently bought a 448 with an Onan p218g. It ran great the day of purchase and I was very happy with the tractor. It came with a deck and snowplow. I loved the power and the utility of the tractor. Well, after I drove the thing back (5 hours), the tractor ran a few times and then wouldnt start. The engine would turn over, but there was no spark from the plug wires. I checked the battery, which 230 CCA, and it had a good charge. I did a resistance check on the coil and the primary winding came in at 3.6 which is within range. I was not able to do the secondary windings with my cheap mulitmeter. I have gotten the tractor started intermittently and at times it runs well, but always seems to hunt at idle. At full throttle, there was a slight miss. Also, the exhaust is very rich and there is usually a very strong smell of unburnt fuel. I checked the plug wires, and the resistance seemed within range. I changed the plugs and it started right up....but now it is only running on one cylinder. When the motor is turning over, I have checked the wires to see if they are firing. Only one side is producing anything at all, and that is not even a "spark", I actually felt it and it was barely a pulse. I am hoping this is an electronic issue and not a major motor issue. If so, I am inclined to repower the tractor. I am not the handiest guy and not sure I can do the motor rebuild myself and a new motor seems cheaper than an Onan rebuild-if I could find someone to do the rebuild.

Please give me some input or advice on this, I am stuck and feeling sick for buying a lemon
 
You didn't buy a lemon.... You bought a used tractor and it developed a problem. Even brand new tractors develop problems but you normally have a warranty to fall back on. In this instance, you are on your own. Forget about re-powering the tractor. That is expensive, complicated and it hurts the value.

You need to diagnose the real problem here. Begin by getting a compression gauge and checking how much compression you have on each cylinder. They should be 90 PSI or better and within 10 LBS of one another. The compression test is important because if you do not have compression on one side, then you may have a broken rod or a hole in the piston or a loose valve seat.

If one plug is not firing, that would account for the smell of unburnt fuel. You may be able to solve this problem with two brand new spark plugs. Checking the ignition wires for corrosion is also important and if the wires are in doubt, then replace them with solid core high tension leads.

The ignition coil is actually two coils that are encased in a single housing. Both coils fire on each full revolution of the engine. One cylinder will have a charge of air/fuel in it and the other cylinder will have burnt gasses in it. This situation alternates back and forth. Coils do fail but everything else should be checked out prior to jumping to the conclusion that the coil is no good.

A bad ignition switch can prevent the coil from receiving full battery power and so can damaged wiring or a corroded electrical connector.
 

Thanks so much for the response, I really appreciate the help. I am a novice with small engine work and can use every nugget of advice and knowledge. I will check the wiring.

As for the sparking issue, should I see the spark when I pull the plug wire and ground it to the block? I can vaguely feel a minor pulse on the one plug but there still is no visible spark, but there is absolutely nothing on the other. Shouldn't the shock that I do feel be a little more jarring?
 
If the ignition system is working properly, the spark should be visible and it should knock you on your butt. The question here is whether the coil is receiving a strong 12 volts or not. I agree that
compression will not affect how strong the spark is that the coil generates but strong compression can suppress a weak spark. You should try monitoring the voltage at the positive post on the coil while
you are cranking the engine to see if it fluctuates. There should be no fluctuation. Section 8 of the manual below might be of interest to you.
P Series manual
 
(quoted from post at 11:58:23 05/26/15) If the ignition system is working properly, the spark should be visible and it should knock you on your butt. The question here is whether the coil is receiving a strong 12 volts or not. I agree that
compression will not affect how strong the spark is that the coil generates but strong compression can suppress a weak spark. You should try monitoring the voltage at the positive post on the coil while
you are cranking the engine to see if it fluctuates. There should be no fluctuation. Section 8 of the manual below might be of interest to you.
P Series manual

So, I tested the coil secondary windings this evening, it was 22,800. The normal range is up to 19,000, so it is not conforming. Also, the motor was still running on one cylinder. I reversed the cylinders on the coil and the other cylinder ran while the other one now sat, so I believe this coupled with the secondary winding resistance being out of whack indicate the need to replace the coil. Am I right? Also, I checked compression and they both came in at 125-130. Finally, the coil pack top is actually cracked, so that may have been an issue as well.
 
All good moves. Now you know that you have a strong engine and that the problem is an electrical issue. The cracked coil cap is allowing high voltage to bleed to ground. I would conclude from those tests that a new coil would be a prudent move.
 

Tom,
Thanks so much for the help and pep talk. I am ordering the coil and will post an update as soon as I get it in. Hopefully thst is the only problem, but either way I relieved that it is only electrical in nature.
 

So I picked up a coil and a condenser this evening. I installed them both and the motor cranks right up and runs on both cylinders. It is running great, but still idles rough and misses at lower rpms. I would think this is the carbeurator, but from what the service manual states, the carb cannot be adjusted.

But either way, thanks to everyone for the help.
 
(quoted from post at 06:34:46 05/27/15)
Tom,
Thanks so much for the help and pep talk. I am ordering the coil and will post an update as soon as I get it in. Hopefully thst is the only problem, but either way I relieved that it is only electrical in nature.

I followed this thread and was gratified to see the way it went; you had a problem and Tom provided clear, concise suggestions and you got your rig fixed. He did a good job giving you some guidance AND no wise guys horned in with non-sensical remarks which is exactly how these forums are supposed to work but often don't lately. :)
 

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