Technical low compressions

[nick0111840]

hi,
i put a new tread on here the other day regarding my fiat marea misfiing,
the spark plugs were black with carbon ,all the coils work,but today a did a compression test on it and the readings were, 1)180 2)30 3)180 4)180
5)120,
:bang:

 

[bulldog5046]

huh, i'm sure its ment to be 250psi on the 20v, i will check

 

[Renegade_8]

A bit low is not the end of the world, but as varied as this shows big problems. To check if it's rings or valves you do a wet then a dry test. Wet involves squirting some oil in the plug 'oles, this temporarily seals the pistons so if you now get good readings valves are good . Take it you have all plugs out, throttle wide open and are spinning the motor on the starter as fast as poss until the reading stabilises?

 

[jug]

To check if it's rings or valves you do a wet test.

:yeahthat:


getting a reading as low as 30 on cyl2 is very bad, it suggests either you did something wrong (just suggesting it as i've seen it happen many times, especially with the push-in testers) or there is something badly wrong (e.g. serious deposit build up on cyl2's valves, a damaged tappet, a badly worn camshaft lobe, a fuct piston ring, a bent conrod, a HG leak etc.)

 

[bulldog5046]

wouldnt worry yourselfs too mcuh, the cars being broken for parts now

 

[Renegade_8]

wouldnt worry yourselfs too mcuh, the cars being broken for parts now

So now we wont know, I would have voted for valves as HG or rings result in visible problems in the oil or coolant.