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TomF

Anti-afterfire solenoid

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TomF
Our AC 616 (equivalent to a Simplicity 5216) seems to have periodic fits when it doesn't want to start. Examining the plugs generally indicates a fuel supply problem. We have good spark with a new Magnetron unit. Barring any blockages in the fuel line and filter, how often do the anti-afterfire solenoids fails or get weak or gummed up in their old age? This unit is a 1985. Any comments from your experience is appreciated. The solenoid tests fine now when we gave it twelve volts from the battery. We're wondering maybe if the contact to the solenoid in the key switch may be starting to go. Thanks! Tom

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PatRarick
Tom, Have seen only one solenoid go bad in 12 years. If you listen closely, you should hear a click at the carb when you turn the ignition switch to the "run" position. You can then assume that the solenoid is working. I would look more towards a fuel pump diaphragm problem. Not the safest, and I would do this only with a cold engine, is to remove the solenoid if you suspect that it is the problem. If no fuel runs out, assume a bad fuel pump diaphragm. If fuel runs out, cover the hole with your thumb and attempt to start. If it starts, the solenoid is bad, working intermittently. If the engine still will not start, clean the carb. Big Six, An anti-after-fire solenoid is a little plunger that extends when the power is cut, plugging the main carb jet. When you shut a gasoline engine down, you kill the ignition. The engine still pulls in full during the revolutions until the motion stops. Since it is not burning this fuel, it is expelled through the exhaust. In certain conditions, the muffler can be hot enough to ignite this fuel in the muffler, causing an explosion. This is called after-fire. At the least, it is a loud bang. At the worst, it will blow out the muffler. The purpose of the anti-after-fire solenoid is to plug the main jet at shut down, preventing fuel from being drawn into the engine. Pat

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MikeES
Tom, I have seen a couple of these solenoids fail. Just remove it. On the Kohlers it is held in place by a thin metal clip. If the engine runs fine without it in place, then you know what the problem is. My Kohler M20 is running just great without the solenoid (I remove the plunger and put the solenoid back in place). Good Luck! Mike S.

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PatRarick
Guys, The engine will RUN fine without the solenoid. It's only purpose is to prevent afterfire when the engine is shut down. The application of the engine is what dictates the need for this solenoid. Some need it, some don't. Without knowing the engine application, I wouldn't recommend running without it. You MAY wind up needing an expensive muffler. If the unit was originally equipped with the solenoid, I would retain it. Pat

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