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Discussion Starter #1
I have been chasing a sporadic issue with my trustworthy 318 that has a B48G transplant (points) for the past several weeks. I am 93% sure its ignition related and not fuel. I get plenty of fuel to the carb and I did a quick carb clean anyway since I hadn't done that in...well ever on this tractor. Choking and spraying carb cleaner in it do not affect it.


At first, it was a few sputters but now its a full blown barely start and not run long. In the past, letting it just sit for a few minutes would clear it up.


I started with the points and condenser which needed replacement. Thought that did it but misfires creeped up again. Replaced the plugs and the wires now as well (it needed both anyway). Still no dice.


I tested the coil but nothing surprising. The primary windings (where the wires attach with nuts to the poles) give 4.5 ohms which is what the manual says is fine. When I test the secondaries (where the plugs go), I get 14.1K ohms which again is within what the manual says of 12.6-15.4 K ohms.


I took the plugs out and I do see spark, but it looks weak to me.


Whats the likelihood the coil is in spec but still failing? Any other tests to perform on it?


I'm happy to buy the coil if that actually fixes the issue, but no need to waste money.
 

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What about a de carbon and valve pm? Coming out of it does not say coil. A magneto or cdi maybe. A b43 coil usually fails hot when its intermitant.

Sent from my LGL52VL using Tapatalk
 

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I had the same issue w my b43g. I put new points and condenser on from JD dealer. I was specific about what my machin, motor was. 318 b43g. The old points were ok but ifigured I would replace will lie I did valves and other stuff. After installing my motor went to poop. Long story short. After working my way from one possibility to another and in complete frustration, I FINALLY tracked my way back to the points. There was nothing else it could be. Period. The points were firing "hot". Or arcing in a sense. Just couldn't get them adjusted. Then I started thinking about how the system works and that led to one thing ....the condenser. The new one was wrong. Did some research and found the right condenser (the values are VERY important) Boom! She purrs like a kitten. I'll find pics and post in a min.
 

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One other thing that you could check while you have the cover off the points is to look for a bare spot on the wire from coil to points that could be grounding out. I had this happen where the white wire goes down through the base plate,just 2" from the points connection. Bout drove me nuts...
 

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Discussion Starter #7
I've been investigating further this morning.

@Bluesplayer007: That is the same condenser that you say I should have. Unfortunately, I pitched the original condenser to swap back in. I found an old one in a drawer from another tractor. I had marked on it "bad", but wasn't sure at the time. I put it on anyways but that didn't fix the issue either. Of course, it could obviously just be bad too.

@Doug_Cartwright: I replaced the wire to the points at the same time I did the points, just to make sure it didn't become a problem. I did recheck just to make sure it still looks good.

I do have a problem with my PTO switch that I have to wiggle it sometimes to get it to turn over. I started the tractor and turned the PTO on just to see what happened. It eventually started cutting out again.

Oh it was 70 degrees yesterday in Indy. Its now sleeting just to make this more fun!
 

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Discussion Starter #8
So I put the new condenser back on. Starts right up and runs fine for 5 minutes until I turned it off. I'm letting it cool back down and will try again.
 

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Discussion Starter #10
@Bluesplayer007 - I agree its worth investigating. I ordered another condenser but from caseingersollparts.com. About same price, but half the shipping cost ($5 vs $10). I've had great luck with OnanParts.com, but shipping is steep on small items.

I am starting to think about just replacing the engine altogether at some point, maybe in the spring. It only has 1150 hours, but was transplanted from a 982 Cub Cadet and the crank swapped. Its always been a little "noisy" compared to other Onans I have heard.
 

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richard
when you tested the coil did you have ALL of the wires disconnected?
also you need to deduct the internal resistance of your meter. ( touch the 2 leads together )

also, the later B 43/48G used the condenser mounted near the coil. ( 312-0256 )

last, you could test the coil cold, and warm when it dies.
thank you. boomer ( the used onan engine parts guy, also NOS and new )
 

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richard
when you tested the coil did you have ALL of the wires disconnected?
also you need to deduct the internal resistance of your meter. ( touch the 2 leads together )

also, the later B 43/48G used the condenser mounted near the coil. ( 312-0256 )

last, you could test the coil cold, and warm when it dies.
thank you. boomer ( the used onan engine parts guy, also NOS and new )
Boomer is the man! Has helped me out.
 

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Discussion Starter #13
@Boomers_influence - I did disconnect all the wires before I did the tests. It was in the 70's outside so the temperature was perfect for testing per the manual. At the time, I couldn't getting running long enough to get it warm for the testing. When I finally did get it running, it was too late and I had to stop to do some other things.
 

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remove points cover and see if only a dim blue spark, orange means bad condenser

Look for pitting, it heavy on one side then condenser is weak

also try putting in a metal nail file in the points to clean them up, I use crocus cloth on mine
 

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remove points cover and see if only a dim blue spark, orange means bad condenser

Look for pitting, it heavy on one side then condenser is weak

also try putting in a metal nail file in the points to clean them up, I use crocus cloth on mine
thats what I noticed when I had the wrong condenser. The points were on fire! Not literally but yeah it was a hot overly strong spark. Proper condenser cooled them down.
 

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Discussion Starter #16
I went out tonight and made no changes. Started the tractor and it sputtered as it had been.

Luckily, I received my NOS Onan condenser in the mail today (seriously, that was some wicked fast shipping). Installed, started the tractor......and purred like a kitten! I mowed about 1/3 of an acre before it got too dark.

So, unless the rough running comes back, it looks like that new condenser I bought already went bad. Full disclosure, it was not an Onan part, so maybe there's a lesson to be learned there.

Hopefully this will be the last post on this subject and I can move on to posting pictures about my soft cab improvement project.

Many thanks for all the WFM'ers input to help work through this!
 

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Cool! Just the wrong values on the non Onan condenser. It limits the fire to the points. Not enough limit means you points run hot. Glad you got it corrected. Happy mowing! Oh and loctite those points when you get them set. Otherwise the will move. Just a dab of purple is enough.
 
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