Low compression in 1 cylinder

I have a 1996 Pontiac transport and my mechanic told me that my 6th cylinder is low on compression. We have gone over everything from changing the spark plugs to looking at the cylinder it self. Everything appears to be just fine. He said the 6th cylinder apears to look fine but the compression is very waek.

Could someone help me figure this out

Have mech do drop down test with oil in cyl read compression to determine weather valve or ring problem. You could have a burn valve or valve seat worn.

Have mech do drop down test with oil in cyl read compression to determine weather valve or ring problem. You could have a burn valve or valve seat worn.

Anything else I should mention. He is going to start working on it again shortly. Lets just say that is not the problem then what next. We have been dealing with this for 6 weeks now and everytime we think that is the problem it is not it.

Thanks for the info

The only thing that will hold compression is the valves closed and sealing, the piston rings not letting air pass by so if there is no comp. in cyl it is either the valves or rings, most likely the valves.

PS. that will include the valve train, rocker arms lifters and push rods, could be bent push rod or busted rocker arm, broken valve spring.