UK Car Repair: corsa wont start, new spark, question thanks

Question
QUESTION: Hi William, iv got a 1.2 corsa n-reg an it when i try to start it, it just keeps turning over it has been stood for a while but before that it was fine and had nothing wrong with it, but now it doesn't start at all or make any attempt to, there is also a lack of compression in 1 of the cylinders, i put new spark plugs in an checked that they all spark properly, an when i took them back out again to check them one of them was covered in white deposits is there anything i can do without having to take it to a garage?  

thank you

ANSWER: How do you know it has a lack of compression in a cylinder? It does sound though as if the timing is out, perhaps the belt broke when you rtried to start it after it had been sitting a while.  You need to have a professional look at it!

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QUESTION: thanks for the reply and i can tell there is a lack of compression in a cylinder because when i try to start it it sounds like i have taken a spark plug out  because there is a break in the sound an the belt hasn't snapped iv had a fairly good look at it my self but i still cant manage to work out a problem for it

thanks for your help

Answer
The belt i'm referring to is under the front cover and likely can't be seen without removing things, I suspect you are looking at the accessories belt. The next step is to do a compression test to see if in fact you have compression on all cyl's,  The simplest way is to remove the spark plugs and move the cables out of the way, now have a friend turn over the engine while you place a finger in front of each plug hole in turn, you can feel if you have pressure blowing out evenly from each.