Briggs and Stratton 18.5 hp ignition problems

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  #1  
Old 10-04-05, 06:41 AM
Ron Katzaman
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Briggs and Stratton 18.5 hp ignition problems

I have a twin cylinder model # 42A707 Type 1238 01 code 9604045B Briggs and Stratton engine. At the begging of the summer I lost spark on one cykinder so I replaced the ignation module with a after market module and it ran fine for a couple of weeks. Then I whent to start the tractor after being parked in my shed for a week or two and it would not start. This time I had no spark on both cylinders so I again replaced the module with the same aftermarket module. Again it worked fine for a few time and then the same thing happened it would not start after being parked for a few weeks. I checked everything from the switch and unhooked the ground wire and nothing. I checked with the place I bought the modules and they told me to buy a Briggs and Stratton replacement module.
I also went into the Briggs and Stratton home page and read there trouble shooting guide and could not come up with a real cause. Then I emailed Briggs and Stratton hoping to get some places to look for a cause of the module failures, but the responses from them were almost useless. almost never answering my direct questions.
I replaced the ignation module with a Briggs and Stratton replacement and removed the ground wire from the ignation switch and replaced it with an independent kill switch to shut the engine down. I did this because this is the only connection of the module to the electrical system of the tractor and now it is completely isolated.
Also does anyone know how to check a ignation module with a ohm meter or other wise. Briggs and Stratton sad you can read between the high tention leads to the stack plates(ground) and it should read about 25,000 ohms, but the new module reads nothing, and I couldn't get an good answer from Briggs and Stratton. Also the person at Briggs and Stratton told me I have anumber of magnets to control when the cylinders fire. My flywheel only has one magnet and I checked it with the screw driver test and it seems plenty strong. Can anyone tell me how the module directs spark to the correct cylinder since there is only one magnet and one ignation coil?
The tractor is running fine now but I don't know for how long? Can anyone shed for light on this problem?
Thanks: Ron
 
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  #2  
Old 10-04-05, 11:24 PM
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Hello Ron!

I think you're on the right track first of all with the new coil/module.

The premature failure of the coil could be caused by either inferior quality parts, or high temperature. On the bottom of each cylinder is a sheet metal shield. It is attatched to the underside of the cylinder with a 5/16" head screw. Remove this screw and the shield and clean out any debris built up under the cylinder and in between the cylinder cooling fins in this area. If these are clogged, the engine will overheat and the high temp is what commonly causes coil failure.

There is only one magnet that affects ignition timing on this engine. The resistance readings you will get on this coil will vary, and there is not much to check with a meter on this coil.
 
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Old 10-05-05, 05:11 AM
Ron Katzaman
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Thanks Cheese

The only question I have about heat is wouldn't the module go out while the engine is running. The last two times the module failed we cut grass for about 4 hours then brought the tractor home and unloaded it and put it away and after sitting for a week or so it had no spark. The tractor did start and run fine when unloading it about 15 minutes after finished cutting.
Do you think that it continued to build up heat after being put in the shed?
Ron K.
 
  #4  
Old 10-06-05, 12:00 AM
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The coil probably gets the hottest after the engine is shut off. The fan on the flywheel is constantly moving air over the coil when the engine is running. When it is off, the fan is no longer moving all that air, and the radiant heat from the engine can better heat the coil. Especially a hotter-than-normal engine.
 
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Old 10-06-05, 06:28 AM
Ron Katzaman
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Cheese
Took shields off the cylinders and they weren't really dirty but I blow the cylinders and heads off with air anyway. Is there anyways of checking if the engine is running hot? It doesn't appear to be and all shields and flywheel fan are in tack.
Ron K.
 
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Old 10-07-05, 12:46 AM
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There's no really good way of knowing how hot the engine is and how hot is too hot, or rather, where the line is drawn. If your cylinder cooling fins are clear, then the problem was likely an inferior aftermarket part. The original equipment coil will probably fix the problem for good.
 
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