Has nothing to do with fuel. It's either the battery or the starter. BUT WAIT! It could be a bad alternator - not charging the battery. BUT WAIT YET AGAIN! It could even be a worn or loose fan belt.
Here's how it works: When the engine is running the belt turns the alternator. If the belt is loose the alternator can slip and not charge the battery. If the belt is tight and the battery is not charging then it could be a bad alternator. If the alternator isn't charging the battery then when you try to start it the battery will not have sufficient power to turn the starter over, thus turning the engine over.
But if the alternator is good then either the battery is bad (not taking a charge) or it could be the battery terminals are loose or dirty. You may even have a bad ground somewhere.
BUT WAIT! I also mentioned the starter. If the belt, alternator, battery and terminals are all good and clean and working then the problem is with the starter. It could be a loose wire on the starter or it could be a bad starter itself. Knowing what sort of car you're talking about would be helpful, but most systems are basically the same.
Since you mention a clicking noise - that clues me into a weak battery. For whatever reason it's weak, that's where I'd start checking things.
I'd get a jump start so I could then test to see if the battery voltage is going up or down. If the engine is running the voltage should go up to 13.5 volts or more. If the voltage is 12.2 or lower and the voltage is dropping then the alternator is not working. Don't try to test it with everything on first. Just get the car started, THEN test it. If the voltage is going up THEN switch everything electrical on that you can. AC, Defrosters, Radio, lights (high beams too). Check the voltage again. If it's not going up then the belt is slipping.
There's just a little bit of logic in decyphering what's going on, but if you can get it running and drive it to an auto parts store, most of them do free battery and alternator checks right there in the parking lot. They'll be able to tell you if you have a bad alternator or a bad battery. Just make sure they check the belt tension too (with the motor off of course, you don't want to reach into a running engine).
Hope this helps.
'av'a g'day mate.
'')