There are several safety switches on the lift that will shut off the flow of fuel if various things go wrong (such as turning over). I don't know the model you have but it's probably one of these switches is bad. When you start the lift, most of these switches are not in the circuit. As soon as you release the start button/switch, these switches are in the circuit and one of them is not letting the lift continue to run. Get out your owner's manual or wiring diagram and start looking and testing. Good luck.
