ZERO psi on compression test wtf??? - Saxperience

stevo1600 · 1st April 2018, 13:52

Just done a compression test and heres my weird results.

Dry test

cylinder 1 = zero

cylinder 2 = 190 psi
cylinder 3 = 160 psi
cylinder 4 = 150 psi

Wet test

cylinder 1 = zero

cylinder 2 = 220 psi
cylinder 3 = 210 psi
cylinder 4 = 200 psi

so clearly i have a HUGE hole some where in the system for cylinder 1 to not create compression.

could this be related to timing? im guessing its got to be something with a stuck valve? even with bad rings, it would still produce some compression...

thoughts??

sri_130 · 1st April 2018, 16:28

Has it just happened or part of a rebuild?

Broken valve spring, I'll go for.

stevo1600 · 1st April 2018, 19:10

part of a rebuild

i never saw this engine run however ive just replaced seals lapped valves etc

defo thinking its something to do with valves because even with a bad head or rings, id still get compression even if very low.

wish i had the means to do a leak down test but i dont

Chipwizards · 1st April 2018, 21:38

Bring it to tdc and blow air down the plug hole, you'll soon see where it's going.

Did you drain the followers?

welshpug · 1st April 2018, 22:28

8 or 16v?

stevo1600 · 2nd April 2018, 01:08

16v

gunna try rig something with a small air compressor tomorrow to see where my leaks at before i rip the head back off.

i didn't drain followers.

MartinObviously · 2nd April 2018, 18:45

Does the piston move in the bore? lol

stevo1600 · 6th April 2018, 20:41

lol xD

yes it does,

ive managed to do more diagnosis and have came to the conclusion it HAS to be top end causing me the issue. i tried a head with no cams in and it produced 60psi on that cylinder!! yet this other head with the cams in makes;

cylinder 1 - 0psi
cylinder 2 - 210psi
cylinder 3 - 200 psi
cylinder 4 - 200 psi

thinking either severe warpage or a big crack some where..

gunna wack those cams in the "good" head time it up and hopefully i have a result.

Chipwizards · 6th April 2018, 23:36

Put a cylinder leakage tester on it, you'll see where it's going straight away.

MartinObviously · 7th April 2018, 10:10

Quote:

Originally Posted by stevo1600

lol xD

yes it does,

ive managed to do more diagnosis and have came to the conclusion it HAS to be top end causing me the issue. i tried a head with no cams in and it produced 60psi on that cylinder!! yet this other head with the cams in makes;

cylinder 1 - 0psi
cylinder 2 - 210psi
cylinder 3 - 200 psi
cylinder 4 - 200 psi

thinking either severe warpage or a big crack some where..

gunna wack those cams in the "good" head time it up and hopefully i have a result.

That's bound to be a visible crack if it's going that fast. that would be one hell of a warp, check it with a straight edge?

Quote:

Originally Posted by Chipwizards

Put a cylinder leakage tester on it, you'll see where it's going straight away.

Pretty much this.

stevo1600 · 7th April 2018, 14:36

If only I had access to air!!

My valve lapping skills are atrocious

Just checked the valves and noticed if I looked down into the intake port I can see bloody daylight so was like errrrrr ok

Chucked some water in the port and in went straight past the valve seat and out the other side. 3 valves clearly not seated on that chamber 🙁 hence no compression!

Go ahead and say it guys, I’m a feckin idiot lol ah well live and learn I should have checked it with the water method before hand I guess.

welshpug · 7th April 2018, 17:06

sounds like you have bent valves from a fitting error, I haven't lapped any valves for years, however I have had them 3 angle cut and they seal beautifully.