Here some things to try.
1) Disconect the fuel line at the fuel tank, if the line is at the bottom of the tank then fuel should run out. If not you probable have a lot of debris in the tank that needs to be flushed out.
2) Follow the line from the tank, you might find a fuel shut off valve, make sure it is on.
3)Next you should find a fuel pump, if the unit has been sitting for three years, it probably needs to be kitted with new gaskets and diaphrams. Sometimes, if you pressurize the fuel tank slightly with compressed air it will prime the fuel pump to get it to work.
4) Recommend cleaning the carb also, if unit has been sitting for three years.
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