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Discussion Starter · #1 ·
This is my first Onan engine and I know very little if nothing about Onan's but willing to learn.

This is on a '74 Case 446, it's been sitting for some time outside.

First thing I did was pull the cylinder heads and make sure the valves and pistons moved and they do, put the heads back on.

Starter was bad so I got a rebuild kit and it works fine now.

Carb was taken apart and cleaned the best that I could, despite sitting for a few years the side was rather clean. It has a aftermarket fuel pump running off the vacum line and it's working as I getting fuel into the carb.

Installed new spark plugs gapped at .25 (champion H10C, old plugs were some other type?)

Didn't have a spark test so I bought one (been needing one for a while) it's inline plug wire with a light. At first I got a little spark from the right cylinder, but it was erratic, no spark from the left.

Plug wires seem loose at the plugs, the was a lot of rust in them, cleaned the insides the best I could but they aren't the standard plugwire I have seen on other brands, the plug boot if offset were the wire enters the boot.

Cleaned points and gapped them (.20), turning the flywheel by hand I'm seeing the points open and close.

I have 12 volt to the + side of the coil, noticed at one point when I left the ignition switch in the run postion, the coil was warm, almost hot to the touch.

Now what? later checking the right side again, I got no spark from neither side, my gut tells me the plug wires are bad and next to replace the points and condenser.

What is the testing procedure for the coil?

Does anyone sell a conversion kit to convert the point and condesor to solid state?
 

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eBoydog,

I have purchased from Kirk Engines a pointsaver. I cannot tell you how it works yet because it is still in the box :sidelaugh:

There web site seems to be down right now:

http://www.kirkengines.com/

They also sell a "point slayer" which I believe eliminates the points all together.

http://www.kirkengines.com/Hyperlink%20 ... ctions.PDF

Perhaps some of the other members could comment on the performance of these products.
 

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The points are nothing more than an on/off switch that are operated by the camshaft during the rotation of the engine. The points turn the coil on and then shut it off. When the coil gets shut off, the magnetic field inside the coil collapses in a split second and voltage is induced into the secondary winding of the coi. thus creating a high voltage that is seeking a way to ground. The spark plug wires provide an pathway to ground. The spark plugs offer the final step to for the voltage to reach ground providing the voltage is high enough to jump from one side of the hill to the other side. We call that the "gap".

Your plugs are likely OK as are the points and condenser but the plug wires sound highly suspect. If you replace them NOW, you remove them from the list of suspects. You do not need resistor type wires. No one watches TV off of roof or tower antennas any more so who cares about RF interference? Push comes to shove, put resistor style plugs in.

The condenser is there to keep the points from deteriorating too quickly. A good set of points and condenser will last you for many years. Point savers do work but payback takes many years.

Right now you need to work on having a fat spark at the plugs. You can go whole hog with new points, condenser, wires and plugs. Not a big cost. If those solve the problem, then you are golden and then it's time to address the carburetion issues. If not, then you need to check the wire from the points to the coil for deterioration and to make sure the coil is still receiving 12 volts while the engine is being cranked. In other words, the ignition switch can also be suspect as can all the connections and wires involved. It's an old tractor. Assume nothing. Suspect everything. Test everything.
 

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eboy
at this time i would add that you download the service manual for your engine from this site.
then you can test your coil.
the oem wires were Wkitacre, they have a red boot on the plug end.
that is where the resistor is located they will be about 15,000 to 18,000 ohms resistance
i switch all of mine to solid core, 7 mm hi temp wires.
good luck. boomer
 

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Discussion Starter · #5 ·
I started back tracking, first I made sure the spark tester I bought worked by trying on another motor which it did, ohm'ed out the plug wires which I got about 16k ohm like Boomer stated, swapped the coil with a Kohler I have and checked for spark which I still had none so then I ohm'ed out the points which I found the plunger was stuck.

It appears there was combination of dirt and possible corrosion at the base of the points box were the plunger entered the engine. After cleaning everything and putting everything back togather, I have spark and the old Onan runs!

It's slightly loud of course with straight pipes but the good news is that there isn't any smoke and no bad noises that I can tell. I'm tickled pink at this point, now onward to rebuild the exhaust!

Thanks everyone for your advice!
 

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Good work!!!!!

That's exactly what diagnostics are all about. Many of us have a tendency to leap to conclusions that a part has failed and then start replacing part after part. You found that the real problem was nothing more than dirt causing the points plunger to stick in one spot. Far too many pieces of OPE get junked because of such assumptions. No one wants to spend the time needed to get to the truth.
 

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eBoyDog said:
now onward to rebuild the exhaust!
I've seen a lot of custom exhausts and most of them leave a lot to be desired but the one on Tom's recant post regarding a custom paint job is worth studying. It appears that it uses 1" copper pipe fittings instead of steel pipe fittings between the engine and mufflers which is a much cleaner look. I also like the mufflers used but they definitely need some support brackets. If you use the copper fittings make sure you braze them or use solder with a high melting point.
 

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Discussion Starter · #8 ·
I think just the flair outlet tips are copper, that muffler he used was fairly easy to adapt as it's slightly larger than the orginal U pipes and from his description over at that other place, he slipped the inlet over the old pipes and he did weld some type of support to the engine.

Made up pair temp mufflers last night using those Briggs round exhaust that have a 3/4 pipe fitting, used a 1" to 3/4 thread reducer to go up into the pipes on mine. I used a couple radiator clamps to hold one on that still had part of the baffle and the other I had to spot weld it keep it on (trying not mess up the orginal pipes if I need them for reference).

I don't have any carb problem like I thought I did, one just needs to tighten those intake bolts better than finger tight when they put the intake back on...
 

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i am in a similiar situation with an onan, i have fire to the + side of the coil, to the points, back to the - side of coil but no spark at the plugs. any suggestions on where and what to check next? thanks to all you people for sharing your knowledge. Oh it is a cub cadet 982 hydro with tractor model # 142984100, ser # 2050589U711802 and engine numbers are mod B48G CA019.9/3707B IF someone can tell me the year i would appreciate it immensely. thanks.
 

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This forum is actually dedicated to Colt, Case and Ingersoll tractors so unfortunately we cannot help you much with questions about a Cub tractor itself. However, an Onan B48 is something that we can help you with and we are happy to do so.

The coil used for Onan engines are constructed with a primary winding of wire that has its ends joined to the + and - terminals on the top of the coil body. If there is no break in that winding, then electricity will pass through it whenever the points close. You will only see 12 volts on the + terminal if the points are closed if you are using a test light. If the points are opened, then you will see 12 volts on both the + and the - terminals and that tells you that the primary winding is at least, allowing current to flow through it.

However, if the primary winding has been severally overheated due to age, then the insulation on the primary winding can fail and allow some of the windings to short together. When that happens, the coil cannot create a spark that is strong enough to jump the gap on the plugs. Keep in mind that it takes a stronger spark to jump the plug gap when the combustion chamber is under full compression by the piston than it does when the plug is laying on the engine in the open air.

There are two secondary windings that can also short and fail. The quality of the high tension leads going to the spark plugs is important. If they are deteriorated, then the even if the coil is working, the electricity can be lost in those leads. Make sure that the plugs you have are correct, in good condition and have the correct gap.

We have Onan Service Manuals in the Tech section also.
 

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Onan Master, new and used parts.
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mws
if you list the engine s.n.
i can tell you the month and year it was built.
you will need a V.O.M. to check the coil. (the manual will tell you how to do it)
if you should need a coil i have them ava.
good luck .boomer
 

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it was taking the person i got it froms word that he had cleaned the points. Iremoved the points a polished them shiny and re installed and set gap and it worked like a new one....thank you great people.
 
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