Return to the Lawn Mowers Forum | Post a Follow-Up

Craftsman 21' self propelled won't restart

Posted by conpewter (My Page) on
Sat, Apr 26, 08 at 15:03


I have a very weird issue with the mower. I bought it used and it's always done this.

It starts up just fine (One pull after a winter of storage...) after using the priming bulb of course. It will run forever until it runs out of gas, just fine. However it won't restart unless you let it cool down for two hours.

Any ideas what may be causing this?

Follow-Up Postings:

RE: Craftsman 21' self propelled won't restart

Check the quality of the spark when cold vs hot.
Don't run it out of gas. Maybe the carb has trouble filling for some reason when empty.

I had an OLD Craftsman years ago that was terrible hot starting. It was probably a bad coil, but if I replaced the spark plug about every 5 hours, it was "bearable".

RE: Craftsman 21' self propelled won't restart

My theory is that your ignition coil assembly is failing after you shut it off by heat soaking. When it cools down it works again. I haven't seen the much talked about "vapor lock" syndrome but some people may suggest that. I vote for a marginal ignition coil assembly. I have so many mowers with marginal ignition coils. If it's cold, wet, or sometimes too hot they won't fire. That's the reason people traded them in I'm sure. If all mowers had a strong reliable spark like today's cars we might be amazed how reliable and easy to start they would be. Anyway.... Do a bit of diagnostics. Next time it won't start quickly pull the spark plug connect it to the wire and lay the plug on the cylinder fins. Have someone pull the rope with everything in the start position and you watch for a spark. (watch out for your toes around that blade) A good spark should be blue on a clean plug. If no spark while it's still hot then I say the coil is bad. If it does spark try a new plug. If it sparks good but doesn't start try a squirt or cap full of gas down the intake to see if it will start momnetarily. If the manual priming test doesn't get it going make sure it has compression. Possibly a valve is sticking when it's hot but I kinda doubt it.

RE: Craftsman 21' self propelled won't restart

I bought a new spark plug and had my wife pull the cord (this is after I ran it for a little while and shut it off) There is no spark so I'm going to order a new ignition coil for it and give that a try. I'll report back, Thanks!!

 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!

Return to the Lawn Mowers Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.

Learn more about in-text links on this page here