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intermittent missfires

Posted by James. iowa (My Page) on
Thu, May 8, 14 at 18:46

i have a 6hp briggs(190cc) quantum with a side draft carb.engine .starts on first pull and runs perfect for the first5 to 10 minutes then develops a intermittent missfire.it feels like a faulty spark plug wire thats jumping to ground occassionaly.installed new plug with same results.engine re starts on first pull with good compression when hot.could the electronic ignition module be malfunctioning after the engine warms up?maybe carbon deposits in the combustion chamber?please help!!!!


Follow-Up Postings:

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RE: intermittent missfires

Could be the coil, although usual coil symptoms are either completely dead (no spark) or will be OK when cold, and then dead when warmed up.

Substituting known good coil is best way to troubleshoot. Replacement coil for 12XXXXX series Quantum engines is Briggs 692605 or 493237. Cost for OEM Briggs is about $35 to $40; Aftermarket is usually $20 to $25 on internet.


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RE: intermittent missfires

You'll have to pull the shrouds to check it anyway, so check to see if the coil worked loose. If loose, put a regular business card between the flywheel magnet and the coil, which is approximately the correct clearance and tighten the coil bolts. Be careful and keep in mind you're threading steel into aluminum - you don't need a 12" ratchet and a lot of strength.


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