sensor?

1948jr · Mar 3, 2017

what is the electric plunger on the carb bowl on garden tractors for and is it important?

Bob · Mar 3, 2017

The fuel solenoid on the carb plugs the main jet when the ignition is switched "off" to prevent unburned gas vapor from being spewed out the the exhaust causing smog and unnecessary pollution, and as a side effect, a possible hot muffler backfire.

Steve@Advance · Mar 3, 2017

That is a solenoid valve that allows the flow of fuel to the main circuit of the carb when the ignition is turned on, stops the flow when the ignition is turned off.

It has 3 purposes:

To reduce emissions by stopping the unburned fuel from going through the engine and out the exhaust while the engine is coasting down when the ignition is shut off.

To prevent the same unburned fuel from accumulating in the muffler, and exploding with a bang on the next restart.

To prevent the engine from "running on" when the ignition is shut off. Sometimes a hot engine will try to continue to run, firing on heat and compression.

Is it a necessity? No, but if it is disconnected or fails to open, the engine will not run. It can be disabled by removing the plunger, the engine will run, but may exhibit the above symptoms.

What it does not do is stop the flow of fuel to the carb bowl, does not protect from a gravity flow fuel system flooding the engine or draining the tank, does not protect the carb from fuel evaporation deposits when stored long term.

Bob Bancroft · Mar 4, 2017

The first time I saw such a thing was a 1966, or 1967 JD 2510 gas.(There was one of each around here) The same wire/circuit handily worked the electric shut off on the diesel injector pump.

Geo-TH,In · Mar 4, 2017

1948jr,
Are they important? NO
What do they do? They are suppose to shut the fuel off to prevent dieseling.
Do they work? No
Instead of killing the spark to shut off the engines, I use solenoid to shut fuel off to a 20 hp kohler and a 20 hp honda.

The kohler won't shut off unless I idle the engine and it takes about 5 seconds before engine runs out of gas. It will continue to run at high speed with solenoid off.

The honda takes about 3 seconds to run out of fuel at high or low speeds.

I have removed the plunger on defective solenoids and engines run just fine.
geo

sensor?

1948jr

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Bob

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Steve@Advance

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Bob Bancroft

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Geo-TH,In

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