[billybek]

Replace the starting relay when you replace the start capacitor.
Usually the capacitors last a very long time but can on occasion go bad. Quite often the starting relay is the problem.
There are two types. Current relay where the start capacitor is connected to a normally closed switch.
This gives the motor a kick in the butt to get it rolling. When there is current draw through the windings the switch opens and the start capacitor is out of the circuit.
The second is a potential relay. These are position sensitive and must be mounted in the direction indicated. These relays are normally open and close with the high starting potential between start and common to put the start capacitor in the circuit. When the compressor amperage drops to its RLA from its starting current the start capacitor is taken out of the circuit.
When I did do some work in the residential side of HVAC I would always replace the starting gear with the factory relay and capacitor.
With compressor on the way out I would try one of the kits just for the heck of it. Sometimes they work and sometimes the compressor is too far gone. YMMV