How do you keep the motor running when you get off the seat? How do you keep the blades turning when you back up?

Before you start removing covers and panels unplug the mower. Turn the mower over and carefully try to spin the blade by hand. Your checking to where the issue is most likely to be.
Does the motor sound different when you pull the Start trigger? If it sounds a lot faster than normal, it could be an issue between the motor and gearbox.
Does the blade spin really easily and feel like it's not bolted down? Does the blade not turn at all like it's 'locked' or 'jammed'?
- A loose or floppy blade is commonly the centre mount bolt for the blade is loose or the blade isn't seated correctly.
- A 'locked' blade could be a gearbox or a motor issue.

get a new ignition switch and safety switch for your deck

Blows 3 times? Explain... Pops 3 times maybe and wont keep running? If this is what you mean, then it is either a timing issue (Flywheel key sheered), or blade is loose or bent. The blade helps to keep the mower running by balance and centrifical force. The blade IS on??? Do you have a link to the actual picture of the mower? Is this a walk behind or rider? Are the blades ran by belts or directly from the engine?

If you can hear the motor engaging but the blade is not turning, there could be several possible reasons for this issue. Here are a few things you can try to troubleshoot the problem: Check the power supply: Make sure the saw is properly plugged in and the outlet is functioning. You can also try plugging the saw into a different outlet to see if that makes a difference. Check the blade: Make sure the blade is properly seated and tightened on the arbor. If the blade is loose, it may not spin properly. Check the belt: If your miter saw is belt-driven, check the belt to make sure it is not loose or broken. Check the motor: If the motor is running but the blade is not turning, it could be a problem with the motor. Check to make sure the motor is properly connected to the blade and that the motor is running smoothly. Check the electrical brake: If your miter saw has an electric brake, it may be malfunctioning. You can check this by unplugging the saw and removing the blade. Then, turn the saw on and see if the brake engages. If it doesn't, the brake may need to be replaced. If none of these troubleshooting steps solve the problem, it may be best to take your saw to a professional for repair.

check the safety switch on the seat

On both screws, turn them in just until they seat, not tight. Back them out one full turn. Start the motor and let it run until it gets up to temperature. If it won't start or stay running, turn the L screw out another 1/2 turn. With the motor idling, turn the L screw in just until you hear the motor tone change then back it out until it smoothes out and keep going until the motor tone changes or starte running rough. Turn it back in half way between these two points. With a blade on the saw, hold the throttle at about 1/2 to 3/4 full and adjust the H screw using the same method.

There is a small gun-metal colored bar (dark gray or black) at the very rear, just below the back of the blade. It pushes inward, in the direction of the blade. Push it firmly in and pull up on the teeth of the blade. It should pop upward. You can then remove the blade from the tongue that it sits upon. When you want to put it back, slide the blade back on the tongue, then, WITH THE MOTOR TURNED ON, push the blade down to its seated position. It will click into place.
Hope this helps you.

There is a small gun-metal colored bar at the very rear, just below the back of the blade. It pushes inward, in the direction of the blade. Push it firmly in and pull up on the teeth of the blade. It should pop upward. You can then remove the blade from the tongue that it sits upon. When you want to put it back, slide the blade back on the tongue, then, WITH THE MOTOR TURNED ON, push the blade down to its seated position. It will click into place.

There is a small gun-metal colored bar at the very rear, just below the back of the blade when it is only the clipper. It pushes inward, in the direction of the blade. Push it firmly in and pull up on the teeth of the blade. It should pop upward. You can then remove the blade from the tongue that it sits upon. When you want to put it back, slide the blade back on the tongue, then, WITH THE MOTOR TURNED ON, push the blade down to its seated position. It will click into place.
If you have taken the blade off and the tongue has for some reason flipped back against the head, slide a screwdriver blade behind it and flip it back out so you can slide the blade back on it.
Good luck

I would check to see that ID of the blade arbor matches the OD of the motor arbor, and you are not missing an adapter ring. Then I would get some acetone and a wire brush clean all surfaces where the blade seats. This is also good practice for Jacobs chucks on drills, that allow the drill bits to spin.

Jim