AC Motor Start Problem

It's busted.

It sounds like your starter circuitry is ineffective. Examine all of the parts of your starter circuit. It may even be that you have too large of a mechanical load to start too. The mechanical failure could be anything from a failed bearing to a misalignment.

Although there might be mechanical binding etc., my first suspicion would be a bad starting capacitor, followed by some control step not working.

It's knackered. I've got plenty of replacements in Dodgy Dave's lock-up on Canvey Island, though. Just send cash. <Splutter, wheeze>

The answer is more than likely in your posted question. Start by qualifying the capacitor, then the switching mechanism.

I am not clear,should i replace capacitors(it is having two) with new one(same capacity) or should i go for higher capacity capacitors

The capacitance value of the capacitors delay the current a precise amount of time compared to the primary current so that a proper higher torque is available during low speed start up. So do not vary the capacitance value at all. You can go for a higher voltage rated capacitors if they are available in a suitable package size but do not change the capacitance value significantly.