I have an 85 with a dead cylinder. Its a 4 cly. The compression ratios are 150 on the first three and then 35 on the last. Bad valve? Piston ring? I drove it home and turned it off and then it never started right again. So I did a comp test and this is what I got.

 

Squirt a bit of oil in the cylinder and test compression again.

If compression gets better, it's rings. If it doesn't, it's a head (likely valve) issue or a holed piston.

 

Pull the rocker cover off and check for valve train problems with that cylinder.