My Privia starts fine and will run only if i hold the starter on other wise it dies after about 3 sec.

Sounds like the ignition switch is worn or the contacts are bad. In the start position the ignition is getting power, but when you release it, the circuit needed is bad.

Is your idle adjusted properly? It might be too low, or your mixture might be a little lean. I'm assuming that it's fuel injected, so these should automatically be computer controlled. It might need a basic tune-up with an intake and throttle body cleaning.

sounds like afew things are contributing. pull at least 2 spark plugs and let us know what the electrode looks like,dry,wet, sot black,milk choc, brown,gray, white with green hue,this will be some kind of base to start from.

Found out air flow sensor switch shuts down fuel pump jumper wire bypass works fine thanks