Vanguard Fouled Plugs

kola

I have a 18hp Briggs Vanguard with 22 hours that has performed flawlessly until I removed the engine from the cart to replace the clutch. Now the engine carbon fouls both plugs in less than 30 minutes of running and the engine sputters and eventually dies and cannot be restarted. Obviously, this is not related to the clutch. I've checked the obvious: choke is fully open, air cleaner is clean, and new plugs (NGK equivalents to the stock Champion plugs).

I have read that the fouling could be caused by a weak ignition, specifically some wire or diode related to the coils. I'd greatly appreciate it if someone could provide some additional information what could be causing the weak ignition, how to diagnose, and how to fix or other potential causes of the fouling.

Thanks

BGW

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1989Marathon

The diodes are there to isolate the 2 coils from each other, so that they can come to a common ignition kill point. One way to check the diodes is to remove the diode wires and check them with a multimeter. If one, or both is shorted, you will get weak spark, or no spark, on one or both cylinders. The other way to see if they are the problem is to disconnect them from both coils. Be very careful when you do this because you will not have a way to kill the motor except for pulling the plug wires, or snuffing out the carb. The diodes are not needed to run, only to stop.

kola

Thanks for the reply. Tonight I decided to open up the carburetor to check for any possible issues before I would start chasing electrical/ignition gremlins. Lo and behold the inlet needle was laying in the carb, separated from the float. Too late to start up but I'm sure that was the problem.

Thanks