No compression on one cylinder

[German Shepherd]

As a brief introduction, I bought a 1973 S3 2.25 petrol about 5 years ago with a plan to restore when I retired, roll forward 5 years and after replacing the chassis, bulkhead, refurbishing brakes, axles etc it was time to see if she would fire up. Initially no fuel was getting from the tank to the pump, so pump was stripped, cleaned and rebuilt,  with fuel now getting to the carb, however she would still not fire up. Compression test time, with 150 psi at cylinders 1/3/4 but zero at number 2 on a dry test, wet test on number 2 also giving a zero reading. Thinking it could be a valve issue, I took the head off, both inlet and exhaust valves on number 2 cylinder look ok, not sticking and seem to be seated ok. The Pistons also seem OK, no movement, no nasty noises when moving up and down and no marks in the bores. 

So the question is, do I regrind the valves back in on number 2, put the head back on pray it was a sticking valve and redo the compression test, or while the head is off, drop the sump and take number 2 piston out and see if there is a problem with it. Or could there be another reason why there is no compression I have not thought of.

As further info,  when she would not fire up and after sorting the pump issue, but prior to the compression test, I set the static timing, points and plugs gaps, and there is a good spark from the coil to the distributor and then to the plugs. It is also new petrol in the tank and I have stripped and rebuilt the carb, initially thinking it could be a sticking float or blocked jet. 

I did see her running before I bought her, albeit she has not been started in the last 5 years. 

Any thoughts, advice will be gratefully received.

 

 

 

[rtbarton]

Zero compression is pretty unusual.  if it was running before and not now after five years it's got to be something that's stuck.

If the head is off I'd do a decoke and valve grind at the very least, and maybe guides and springs.

Pour some oil in #2 and see if it drains away more quickly than the other cylinders, if so you may have broken or stuck rings.

Inspect the head gasket for damage.

[Bowie69]

I'd suspect either a stuck valve or an incorrectly adjusted valve clearances.

[German Shepherd]

Thanks for the help. I did not mention in my first post that I had previously taken the head off, removed the valves, de coked, replaced the valve seals, reground the valves in and replaced the head gasket. At that stage all seemed OK. 

I have taken rtbartons advice and poured some oil in the bores, albeit there does not seem to be any noticeable difference in levels, I had also done a wet compression test on number 2 cylinder and when I took the head off a day later, the oil was still in the bore which makes me think that the rings are ok. All four pistons are moving freely and nice and tight in the bores.

I am thinking that I will regrind in the valves on number two cylinder, replace the head and see what happens on a fresh compression test, I can alway take it off again if I am no further forward, drop the sump and pull number two piston out. The joys of retirement!!

Once again thanks for your help.

[rtbarton]

I've forgotten what the inside of a SIII cylinder head looks like, but in general terms you can get a good idea if the valves are sealing by inverting the head and filling the combustion chambers with petrol.  Obviously with the springs fitted.

[timppl]

First thing that occurred to me is a sticky cam follower holding a valve open.

Tim

Edited May 18, 2019 by timppl
Edited because of sticky keyboard :-(

[German Shepherd]

Thanks rtbartons or your advice, I will give it a go.