i have a briggs & stratton, mod. 385777 type 0349 e1. it will start & run fine most of the time, then it will stop firing on 1 cylinder. yesterday it ran fine for about an hour & half, then when i took a break it started skipping on 1 cylinder when i restarted. when i checked the fire it wouldnt arc to the plug & only arc about a 1/16 to 1/8 inch to ground. just installed new coils. any ideas as to what the problem is??
You didn't mention anything about using new spark plugs so I'll start there and recommend two new spark plugs. Also, try using a spark checker instead of the spark plugs making sure you have a good ground on the spark checker.
If the design will allow, swap the coils from their respective positions and try again. If the problem moves with the coil then you know you have a bad coil. If not, you have gremlins.:laughing:
Been there, done that, got the T-shirt, sold it at a garage sale. Things like this can be so frustrating. Please let us know what ultimately fixes the problem.
Check the kill wire that goes between the two coils. You may find a small cut or abrasion which will allow that coil to short out when the engine warms up.
At this point anything is possible and you need to double check everything. So many times the problem turned out to be something simple, something overlooked, and that is why nothing is being left to chance.
Three things I would do. When the engine is running rough, insert an inline spark tester between the coil and plug, to see if you are getting spark. If it is intermittent, or there is none, remove the kill wire from that coil and see if it changes. If it does, you know that something is grounding out that coil. If there is still not spark, the coil is bad. You if the spark is good, take a can of spray carb cleaner and spray around all of the intake gasket areas. If the engine speed changes, you will have found an air leak that is causing the problem and a gasket needs to be replaced.
When my Intek died I pursued the usual suspects and finally found the unsual (to me). One cylinder had stopped firing. Compression was ok. Finally I observed that the exhaust valve was only opening about 1/8." Long story told elswhere in this forum. Exhaust cam had been ground to a round journal because the valve guide loosened and moved upward. If all else fails look at the valve movements.
