Small Engine Ignition Module

[EW1947]

I have a 14.5 hp Tecumseh engine on my riding lawn mower -- but no spark at the plug. After tremendous amounts of troubleshooting I blame the ignition module. Note: I've disconnected the grounding cutoff wire, and there are no other wires on the module excpet for the spark plug wire. My problem: with a spark tester connected to the spark plug there is only a dim flash of light. However, when I connect the spark tester directly to motor ground, there is a bright flash! I've changed the plugs out several times. This sounds to me like the module is producing a diminished output which is strong enough to light the spark tester but not enough to fire across the spark plug. BUT....... I had thought these modules were either totally GOOD or totally BAD, period. Please, any comments? Am I overlooking something? Note: the magnets on the flywheel seem quite strong. The air gap is perfect. HELP!! Thanks.

EW

[Chris Lewis]

According to :

Sounds like a poor connection on the module. Ie: bad ground.

[EW1947]

Thanks Chris, but there are no ground connections on an ignition module like this. The only connection is the spark plug wire. The module is mounted on the engine frame (good solid mount). There is an engine cutoff wire that goes to the starter switch, but it is presently disconnected for troubleshooting purposes, according to the manual. Bottom line: I do get an output but not a strong one. Perhaps a shorted coil winding inside the potted module that allows only a portion of the inductance to be used...?

EW

[Andy Asberry]

A very helpful Tecumseh rep hangs out on the yahoo group Tecumseh Engines. You have to join but you will get the best advice.

[Don Young]

You have pretty well answered your own question. There are no other components to that system other than the magnets, module, leads, plugs and kill switch(es). They can produce a weak spark, sometimes one strong enough to jump the plug gap but not strong enough to jump the gap under compression and ignite the fuel mixture. A strong spark can be created, but at the wrong time, if the flywheel key is sheared. I think your module is bad. [I have been wrong a few times. :>)] Don Young

[mm]

Have you tried using a spark plug as a tester? Unscrew it from the negine, connect it back to the wire, and have someone hold the metal threaded part against the block, or use a wire with aligator clips on each end.

IIUC, it's harder for the spark to jump the gap when the gas in the cylinder is compressed, but not that much harder.

I don't trust your tester. How much did it cost, and what is the essence of it,. I have an incredibly cheap one, with a flashlight bulb or neon light in it, I forget. I think a test with the spark plug is a better test.

I have 7 broken mowers this year, and two seem to need magneto coils. But I'm not sure. When I had no mower, I would have eagerly spent the money, but 2 or the 5 now work. Still, I can't throw the others away, even though the original owners did. (They look new)

(I've given two to a repairman nearby.)

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[LoneStar]

mm...........

Yes, I have used several spark plugs to test the module -- and thanks for mentioning it. There is no bright spark at all when grounding the bottom of the plug (sometimes I get a faint flash). The spark plug tester cost me over $18, but as you say it is not as good as the plug method. After all the helpful responses I'm convinced it's the ignition module. In fact, I've paid for and ordered it, and I can't get my money back if it's NOT the problem. But it can be nothing else!

Thank you all!!

EW

Note: I've removed my original messages from the Gmail newsgroup, since Gmail insisted on using my email address as my "nickname." Grrrrrrrr...... Here comes the SPAM!

[LoneStar]

I'm on my way!! Thanks.

EW

[Mark]

make sure there is no spilled gas around when you do those tests

Mark

[Chris Lewis]

According to mm :

This is a reasonably reliable (and easy) test. However, it still may not be enough spark.

The proper way is to see if the spark will jump a full 1/4". Our small engines instructor has a tester made in the following way:

Take a spark plug and saw off the threaded portion, leaving central insulator and spark gap center pin intact. He then fastened a small bracket with a screw in it, so he could adjust the gap between the screw and the spark gap center pin. A grounding strap with alligator clip is then fastened to the body. Attach the clip to the motor frame, the spark wire to the top of the modified plug, and see if you can pull a spark across the 1/4".

[rdglide03-dbasedos]

I am a curb trash scavenger also. Gasoline engines must have gas, spark and compression to run. Most engine problems I've pinned down have been no spark or low compression. This excludes the normal dirty carb and dirt in gas tank. Squirt a little gas right into the carb. (not in a closed area) If that doesn't help. Check for spark. If spark, check compression. Compression has to be above 70 psi. Lot of times it will run with low compression and 1/2 to 3/4 choke but not well.

[mm]

I was never sure a lawnmower should have such a good spark (compared to a car). I'm happy to hear that it does.

Is this also true with the points and capacitor ignition on a lawn mower (and not just the electronic ignition)?

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[mm]

I never caused a problem with a lawnmower, but I once was testing the spark of a V-8 by holding a plug against the block, while to save time, I was also spraying ether. Don't do that.

The thing blew up with a big bang, blowing the valve cover lip up at 3 or 4 places between bolts.

Fortunately, I'd learned not to move, or I would have banged my head good on the metal edge of the hood.

I was fine, but I had to replace the valve cover. Since I knew of no junkyards in NYC, I had to go to a speed shop, and my brother had one chrome and one regular valve cover until he finally sold the car. (I hope he remembered to give the buyer the other chrome cover.)

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[mm]

That must be a lot better than mine, which cost iirc one dollar!

One of my chores for today is to connect it to a known working mower and see if it lights up. If that doesn't work, I'll try it again after dark and see if it lights up then. :)

That's the way I feel about those two mowers, but I've run out of time this summer. Another chore today is to make shelves for the mowers and stack them up in two piles of two and one pile of one. I'm not making a shelf so much as putting a 4x2 foot sheet of t1-11 on top of one, and then balancing the other on top of that. I had one last winter covered with plastic and a board, and it was clean as new when spring came.

Donm't know much about gmail. or biology or geometry.

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