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loss of compression on cyl's 4 and 6

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Mar 31, 2009, 5:20 PM

Post #1 of 2 (774 views)
loss of compression on cyl's 4 and 6 Sign In

hello everything

1991 chevy Lumina, 3.1L with 240000miles

Question compression on cylinders 4 and 6 i have not yet checked the back cyclinders.

Car broke down on the highway at 75mph. towed home. did an initial compression check and found none on those cylinders except on cylinder 2. So i checked for spark, ok. Then i proceeded to check for valve action, None. OK I GOT IT NOW!! installed new timing chain and gears. AWESOME it should run now. But it dosn't. so i continued on with my tests and installed a compression tester on cylinders 2-6 and found #2 at 145lbs and #4 and 6 with absolutely Zero. Won't even flicker the guage. So i continued with a leak down tester. I put a 100lbs to it and hear a little blowby on the rings and nothing through the coolant or valves. Piston travel is definitely happening. Valves and timing are spot on. checked and rechecked the valve timing with two different sources of information. this engine is driving me bonkers and would like some input to as why this is happening. if i left any information out for your conclusion. let me know and i'll post it. thank you

Loren Champlain Sr
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Loren Champlain Sr profile image

Mar 31, 2009, 6:47 PM

Post #2 of 2 (769 views)
Re: loss of compression on cyl's 4 and 6 [In reply to] Sign In

trevor; Did you do a wet test on 4 & 6? It's possible that they are just fuel washed. If still no compression, remove the valve cover and note rocker arm travel. This isn't an 'interference' engine, but it is 'possible'. 145# on #2 isn't anything to write home about, but enough to run. Will the engine start and run, at all? Might be interesting to get the other three cylinders' pressures, as well. With #4 & #6 next to each other, it 'could' be a head gasket, leaking between the two cylinders. Hope not.
SW Washington

loss of compression on cyl's 4 and 6

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