Lost compression on cylinder 1

[danny_l_2005]

I lost compression on cylinder 1 and have compression ranging from 120-130 on other pistons. Car was working fine before then I changed the valve seals. Keep in mind last time I used my car was at least 6 months ago. I did prime the engine before turning it on. I used my compressor to put pressure on cylinder 1 and it couldn't hold any air, it was going to the crackcase.

I removed the head today valves look fine. The cylinder wall look fine with no scratches. My question is what do I do next? How do I know if I need to bore the cylinder walls or just rehone it and put new rings? What equipment do I need. Thanks.

 

[BoredDSM]

Did you warm up the engine before performing the compression test? You would need something to measure the bore of the cylinder.

 

[danny_l_2005]

I couldn't warm up the engine because the engine wouldn't couldn't stay on more than 30 seconds because cylinder one wasn't keeping any compression at all. What tool do I need to measure the bore of the cylinder and piston? If the cylinder is fine can I just rehone it and use new rings?

 

[BoredDSM]

You would need a bore gauge and some micrometers. Yes, you can rehone it and just use new rings but if its just cylinder 1 I think it should start. A lot of people can start there car on two cylinders so there must be something up with the other cylinders too. You should perform a wet test and a leak down to confirm its the rings. Could be a head gasket, bad valve, or your piston rings.

 

[oVaBoost]

rebuild your bottom end and go from there.

 

[gurmanator]

if it was bad rings you would still have some compression.sound like the valves arent closing all the way,you said you changed valve seals maybe one of the valve seals is making the valve hang up and not closing all the way.a burnt valve or a hole in the piston will give you no compression.

 

[danny_l_2005]

As I mentioned before I did pressurized the cylinder and all the hear was leaking to the crackcase, if it was the valves air would leak either through the intake manifold or exhaust manifold. I wouldn't keep the air for one second as it would all escape.

No hole on pistion, valves look great, valve seals were lubed before installation.

I already removed the head so I can't make a compression test again. Other cylinders as I mention were at around service limit.

Thanks boredDSM ill go get a bore gauge and those micrometers.