engine not starting after sitting for a few months?

Hi,

My son's car cut out when he was on the way home a few months ago. After a bit of fault finding and stripping the car down, I found a snapped lower timing chain.

I replaced this and put it back together, but it cranked, almost fired but then seemed to stall.

After checking the pressures on the cylinders, they were 360, 300, 250, 210 (from back of engine to front). I stripped the engine down and did a leak test on the valves and found that all cylinders were leaking from various valves. I spent a day re-grinding them to stop them leaking. They are now 250, 295, 290, 285 (back to front).

I put it all back together again but still only get the crank and almost started. I tried another camshaft sensor as this message did pop up on my diagnostic tester but only once after re-assembling, it did not pop up subsequently and I was clutching at straws.

Am I looking at a sensor issue? or do you think this is still a mechanical problem? Any help would be most appreciated. The engine is not running?

Many thanks

Kevin