No compression in 2nd and 3rd cylinder

vikasintlvikasintl Member Posts: 26
edited November 2015 in GMC
1989 GMC s15 automatic 4 cylinder ...

I found that there is very low compression in 2nd and 3rd cyl. like about 0 psi or 5 psi but 1st and 4th cyl. have 125 psi

is 125 psi ok or it is sill low?

also, truck was not running ...can it run on 2 cylinders?

and is there any other reason why it shows very low compression in 2nd and 3rd apart from either valves or lower engine problem?

Before I take it apart...I want to make sure nothing else is causing this?


  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    A cylinder will still fire at about 85 psi or above, but of course the higher the compression the more the efficiency. A loss of compression between two adjacent cylinders is traditionally interpreted as a bad head gasket or as a crack in the cylinder head perhaps.
  • thecardoc3thecardoc3 Member Posts: 5,547
    A cylinder leakage test would be the next step to see where the air is leaking from.
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