Well, it does start... sometimes... But sometimes no buzzing from the fuel pump, and it wont start... relay? Ignition? Pump is ok! Must be the wiring... It's a 1.1 55, 1997...

everytime when you turn key you should hear fuel pump noise, also what do you mean doesnt start, is it cranking?

We do need more information.

Fuel pump should run until the requested pressure is reached, then cut if the engine doesn't start.

If cranking, check for spark and fuel dribbling onto the throttle body while cranking.

Check inertia cut off switch-if fitted with one.