Hello my fiat punto sporting sum times starts and sumtimes doesn't , got new battery today , but still wont start unless i jump start it, had alternator checked and thats fine. cleaned wires conected battery but still having problems. Any ideas ?

Put the jump lead between battery -ve and the engine block. If that helps the earth cable connecting the two has dirty connections. there are three earth lead connections including the battery.

If its the same it may be the starter motor.

If it spins over but wont fire it could be the immobiliser or the driver's foot on the accelerator pedal.

If it turns over at a reasonable speed there's no issue with battery or starter motor - the issue has to be immob, fuel (cleanliness, pump, injectors, ECU), ignition (ECU/sensors/coils/leads/plugs) or compression (HG, valves, rings).

If it turns too slowly to fire, the issue is somewhere in the chain of battery, wiring to starter motor (including earth the engine/transmission), or starter motor.

It's nothing to do with the alternator. That's just to charge the battery and power all electrics when the engine is running.

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I've just had my crankshaft sensor replaced. Problem: intermittent starting, then ultimately no starting.

Not saying it IS that...but if you take it to a garage, it helps to have as many ideas as possible