21.5 Briggs running on one cylinder

[brinkkl2000]

This is a strange one to me. I am only running on one cylinder. The dead cylinder has spark, as verified by 2 new spark plugs grounded against the engine, in line spark test, and spark gap test (jumping the gap from 3/8" to 1/2".) I have unplugged the kill wires from both coils with no change, tested the diodes in the kill wire, compared the ohms on the coils to each other and both are almost exactly the same. Did not do a compression test, but did a leakdown test with 0 leakage anywhere. Pulled the valve covers and checked clearances and both were good. Both valves are moving freely and I don't see a valve guide pushed out. Sprayed carb cleaner all around the intake and found no air leaks. I am kind of at a loss for what else to look for. I can pull the plug wire off the dead cylinder can see the spark jumping from the coil to the top of the plug. Any more ideas?

 

[Boobala]

This is a strange one to me. I am only running on one cylinder. The dead cylinder has spark, as verified by 2 new spark plugs grounded against the engine, in line spark test, and spark gap test (jumping the gap from 3/8" to 1/2".) I have unplugged the kill wires from both coils with no change, tested the diodes in the kill wire, compared the ohms on the coils to each other and both are almost exactly the same. Did not do a compression test, but did a leakdown test with 0 leakage anywhere. Pulled the valve covers and checked clearances and both were good. Both valves are moving freely and I don't see a valve guide pushed out. Sprayed carb cleaner all around the intake and found no air leaks. I am kind of at a loss for what else to look for. I can pull the plug wire off the dead cylinder can see the spark jumping from the coil to the top of the plug. Any more ideas?

Does the dead cylinder "fire" if you remove the plug and introduce a small amount of fuel and reinstall the plug ..??
I'm thinking ..since you have spark ..you must be lacking the fuel ...

 

[NorthBama]

Good morning Boo jolly on the spot this morning. You are correct sir fuel, spark and compression also

 

[Tinkerer200]

I suggest you remove the valve cover of the dead cylinder and check out the push rods. IF you find the problem I think you will, I can help you.

Walt Conner

 

[bertsmobile1]

And for the benefit of any one reading this entire thread.
Yo can not test a modern self switching coil with an OHM meter.
They all have a micro chip in there that controls the firing some of these chips can be damaged by cheap multimeters and because of the chip the readings are meaningless.

 

[brinkkl2000]

Thanks for all the tips. This was a real newb maneuver. The carb was plugged... I looked at this carb the way I look at many, of course now I know not all, mower carbs. One circuit in the carb will feed both cylinders. I decided to take the carb off and to my surprise on this particular engine there is a fuel circuit for each cylinder, and the offending cylinder had a partially clogged jet. She is running smooth now.

 

[Boobala]

Thanks for all the tips. This was a real newb maneuver. The carb was plugged... I looked at this carb the way I look at many, of course now I know not all, mower carbs. One circuit in the carb will feed both cylinders. I decided to take the carb off and to my surprise on this particular engine there is a fuel circuit for each cylinder, and the offending cylinder had a partially clogged jet. She is running smooth now.

THANK YOU for the up-date with your outcome, this can be helpful to members with the same issue ...:thumbsup:

 

[motoman]

jolly good thread and outcome