Tecumseh Engine no spark

finkstrMay 21, 2013

I have a Troy Bilt tiller withe the HH60 6hp Tecumseh engine. I was unable to start it this spring so I checked the fuel supply and found it ok. Next I checked for spark and found none. Given that the tiller is quite old - early 80"s, I decided to do a complete tuneup. I replaced the plug, condenser, points and coil and cleaned all contacts. Still no spark. I checked the "ground off switch" and found it ok, not grounding unless the throttle is closed all the way. However just in case I removed it totally. STILL NO SPARK! ANY SUGGESTIONS???

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ericwi

The high voltage pulse is generated by a magneto coil, and these units are subject to failure as they age. You can get the coil tested at a small engine shop that works on outboard motors. They should have a dynamic coil tester that will tell if the coil is working, or not. Coils are degraded by corrosion, and also by insulation failure. A bad connection somewhere is another possibility.

    Bookmark   May 22, 2013 at 8:17PM
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finkstr

Thanks so much for the info. However I need a little clarification. Is the "magneto coil" you refer to the same component usually referred to as the "coil"? If so I replaced it along with the condenser, points and plug. Honestly/ This is driving me NUTS!
Thanks again!!!

    Bookmark   May 23, 2013 at 6:45AM
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ericwi

To generate a pulse of electricity, you have to move a magnetic field across a winding of wire, or move a winding of wire through a stationary magnetic field.
In this case, there is a small permanent magnet fastened to the flywheel on your HH60 engine. If the magnet has somehow separated from the flywheel, and is missing, then there will be no pulse generated, and no spark. As a more general note, when the magnetic field is moving, and the coil is fixed, the device is called a magneto, or alternator. If the winding rotates, and the magnetic field is fixed, the device is called a generator.

    Bookmark   May 23, 2013 at 10:04AM
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finkstr

Thanks for the information as well as for the explanation. I inspected the flywheel when I replaced the points etc and the magnets seem ok,although slightly pitted. Also I made sure that the magneto was in the same place when I re-installed it. Given that the flywheel is keyed to the engine shaft, there is no possibility to install that part incorrectly. I also inspected all the wiring, looking for frayed wires, pinching etc. Everything seems ok. However, I do intend to take it apart again today and check everything once again. Any other suggestions on things to look for?

    Bookmark   May 23, 2013 at 10:58AM
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mownie(7)

Make certain that nothing is somehow "grounding out" the points contacts.
With the points gap OPEN, and the connecting wires of the condenser and primary circuit REMOVED from the points, test for continuity from the wire post to ground. There should be no continuity at this point.
If continuity is present (with points open), something is amiss in the insulator materials that keep this section of the points.......er, insulated/isolated. If there is no continuity until points are closed, everything about that is OK.
Condenser might be faulty and killing the spark.
Condenser IS NOT NECESSARY for creation of a spark, it is there only to increase the life span of the breaker points.
Unplug the condenser wire and leave the primary wire connected.
Spin engine and watch for spark. If it sparks with condenser out of the circuit you have a defective condenser (or the wrong capacitance value).

    Bookmark   May 23, 2013 at 11:41AM
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ericwi

I found a reference to a batch of bad magneto coils. These were brand new units, out of the box. You might have a defective coil. It can be tested with a volt-ohmeter. Well, at least you can verify continuity with a VOM.

    Bookmark   May 24, 2013 at 8:08PM
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fixingthings

Hi. I have the same events. I put a new magneto coil, spark plug wire, new plug, condenser and points. I rotate the flywheel by hand and get no spark. Then (can't explain why), I attach a basic electrical test light with one end in the spark plug and one end on the engine. I then hand turn the flywheel and get enough spark that causes me to drop the plug out of my hand. What am I missing to get enough spark to start this thing? Thanks.

    Bookmark   June 7, 2014 at 4:40PM
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bill_kapaun

The voltage required to fire a spark plug is much higher than required to knock you on you keister.

    Bookmark   June 7, 2014 at 7:57PM
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fixingthings

@Bill.....correct.. I gave the description with the hopes that it would lead someone to think of what would be preventing any spark from happening, but then with the light tester, some spark happens.

    Bookmark   June 9, 2014 at 10:22AM
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mownie(7)

The part of Bill's reply that you might not understand is that a pulse of energy (voltage) from an ignition coil can be so weak that it will not arc across an open space, thus creating a "spark". A simple pulse of energy is not a spark.
But even if it is too weak to create an actual arc, it still has enough voltage to be felt by a person.
Basic test lights are not the proper tool to use when assessing ignition problems regarding spark output.

I suggest you read all of the thread above once more to see if you might pick up on something to help you find out why your ignition output is so weak.
Disconnect the kill wire from the magneto and see if spark occurs then.
If spark occurs with the kill wire unplugged, there is a fault in the kill wire circuit that is stifling the magneto from making a realistic spark.

This post was edited by mownie on Mon, Jun 9, 14 at 12:08

    Bookmark   June 9, 2014 at 12:04PM
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