No spark ignition


Old 07-15-03, 09:00 AM
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No spark on Briggs & Stratton 4hp

I've tried some ideas I've seen on this forum to get my mower started, but I still am not getting a spark.

I have a 4hp Briggs & Stratton - I think it's 173 cc - on a self-propelled push mower. This spring it was difficult to start so I put a tune-up kit in it (points & condenser). That made it start a lot easier and it ran just fine. The next time I tried to start it, it would not start. The shear pin is OK. It spins easily (like normal - not easy enough to indicate a lack of compression). It's definitely getting gas into the cylinder. It's just not sparking.

A friend suggested that maybe the new condenser went bad, since that's happened to him before. So I put another set of points and condenser in it, gapped to .020". No spark.

I tried a new spark plug - no spark.

The next thing I tried is a new coil, gapped to .010" from the flywheel. Still no spark.

I cleaned the magnets on the flyweel, even though they didn't look bad. Still no spark.

To check the spark, I have the plug connected to the wire with the threads touching the metal near the spark plug opening. Am I checking this correctly?

What would suddenly fail from one mowing session with the engine running just fine to no spark on the next attempt to start? What can I check next?

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Old 07-15-03, 11:11 AM
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Hello and Welcome jcd to the Do-It-Yourself Web Site and the Small Engine forum.

I suggest getting back to the diagnostic basics. Check the kill switch. It may be grounding out. look for and check for possible ground on any safety related devices if equiped with any.

You're checking the spark plug for spark correctly. Make a few of the basic tests for ignition as suggested in the already asked question pertaining to spark igntion problems found in this forum.

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Old 07-15-03, 12:55 PM
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Thanks for the welcome and the reply.

It's a older mower - not sure what year, but I got it used 7 years ago. There's no kill switch or any safety devices on it. I checked to see if the insulation was worn on any of the wires that would ground something out. Everything looked OK, but I'll go over it again.

In the meantime any other ideas are very welcome. This thing really has me stumped.

Old 07-15-03, 01:40 PM
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Kill switch does not imply a physical switch or button, key etc. per say. However and wherever the ignition system is grounded to kill the engine is the part or place to check for any grounding.

Place to check could be and most likely on the speed lever cable assembly on the engine. Usually a visablely seen moving part that comes into contact with a wire in a clip, etc.
Old 07-15-03, 07:41 PM
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It sounds like you have covered the basic. There has to be something your overlooking. If we had a model number of your engine we may be able to help you. There should be a model and type number on the blower housing.

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