Low Compression - advise from Haynes Service Manual
Okay, looked through my Haynes manual... healthy compression readings should be around 10-11 bars, that's 145-160psi. And I summarises the following tips:
If the pressure is low, squirt a teaspoon of oil into that cylinder, if the compression figures improved, you have bore or piston wear. If there's no improvement, it suggested leaking/burnt valves, or blown head gasket.
If there's low reading from two adjacent cylinders, it means the head gasket is blown between them, should have coolant in engine oil also in this case.
If a cylinder is 20% lower than the others, and slight rough idle, a worn camshaft lobe is the like cause.
Low compression on 1st stroke, but gradually/slowly increasing on succesive strokes, it means a worn piston ring.
Low compression on 1st stroke, but does not build up indicates leaky valves, blown head gasket or cracked cylinder head. Deposits on the underside of valve heads can also cause low compression...
