mk won't start

hi all , it's been a while. I'm not a rich woman so I am hoping someone can point me in the right direction with my problem. My '85 mk used to start no worries , then it needed a little boost via jumper leads. Sometimes when i drive it and turn it off it won't start again without a jump. Do you think its the battery or alternator. I was going to test it with the volt meter but the battery in that is dead too Bang Head. What are your thoughts before i spend money on a new batttery.

How old is the battery? How often and how far do you drive?

battery would be about 3 or 4 years old , and doesn't matter how long you drive it for. Does it whether you just go to the shop or drive for hours

I'd say your up for a new battery but best bet would be to get a working meter so you can measure the voltage at the terminals when you car is running, your alternator should be cranking out approx 14V while your engine is running.

I am now leaning towards the starter motor as it is just clicking like it won't engage when i try to start it. i charged the battery over night , tightened it all up , got a good reading for the volts on the dash , had a friend kick it over while i listened under the bonnet

What does the volt meter in the car do while you crank it? If it drops below 10v then the battery is shagged

thanks , i will try it again and have a look

The issue with the starter is it won't crank without some heavy Juice. If the batterys not charging there's no juice(prob alty), check for loose terminal connections on the back of the alty,starter or battery, could be an easy fix. Just be carefull spinning spanners round the back of the alty and starter crossing terminals is not good. your best bet is too ring a auto electrician
ask them if they'll diagnose the issue and take it from there. Any decent auto lecy shop will do this, It's like a free quote.

Forgot to mention a little spray of inox in the dizzy cap and on all the connectors might help.

finally got my voltage meter working and the battery is reading 12 when not started and 5 when you try starting it. i will have to jump start it then get another reading while its running and let you know. also i put new battery terminals on today as the others where a bit shagged , jump started it and took it for a run but it wouldn't start again without a jump.