need help with compression test readings......

[eschneider]

On a Geo Tracker 4 cyl:

with all plugs removed:

cylinder 1 - 150#
cylinder 2 - 0 (nada, nil, zip)
cylinder 3 - 150#
cylinder 4 - 160#

with #1 & #3 plugs re-installed: same results

with 30wt oil down the #2 hole, I get 40# of compression.
wait 30 seconds, test again, 10#
wait another 30 seconds, re-test, nada. Zero compression.

What the heck?

I've never seen 0 compression before.....

oddly, the #2 plug looked nice and tan. No hint of oil-fouling.

Sorry if this is posted in the wrong forum? I posted it in the pub, too.

 

[DrEntropy]

Wow, Eric! And this thing RUNS?

Rings catastrophically disintegrated?

...I'm grabbin' at straws here. I have seen zero compression, but only because a piston had a great-giant hole burned in it.

 

[AweMan]

Im guessing broken ring in #2
Oil would not fill a hole in piston unless it was a minute hole {could, I suppose; be a cracked piston tho}
Oil would deffinately not seal a stuck, burnt, bent valve.
Could be a burnt head gasket {cheapest fix senerio} hopefuly this is all it is.
I would deffinately NOT run that engine any further,
IF it were mine Id be ripping the head off to have a look see!
J.M.H.O.
Kerry

 

[racingenglishcars]

Check Valve Adjustment First.

I would say a burnt exhaust valve. Enough oil could seal it a bit, but not long. Zero is a bit low even for a moderatly burned piston, unless it's completely burned down the side, and then oil fouling would probably be present. A head gasket could leak out the side of the block and not to the adjacent cylinder. Usually they will leak to another cylinder at which time two cylinders have no compression.

Check Valve Adjustment First. Then when it's ok, the head comes off for further diagnosis.

 

[eschneider]

the mystery gets deeper.

pulled the head today. Before I pulled it, I checked that the valves were moving OK. Nothing suspicious.

I was shocked at how clean the cylinder walls were. no scratches at all. No ridges at the top of the cylinders. Pistons looked fine. Combustion chambers looked fine. No obvious signs of a head gasket leak.

something causing ZERO compression should have been obvious.

the only thing I can think of that there were some heavy carbon deposits in the combustion chambers, and that this was keeping one of the valves from closing all the way. The valve heads and stems were all clean.

Of course, I'll have the head pressure-tested by a machine shop, but in the meantime - I'm totally mystified.....

 

[eschneider]

not only does it run, but my dad drove it 90 miles from DC to Bunker Hill, WV......

I started it up, and it just sounded like a bad miss. No clatter, no knocking......

Honestly, we have beat the heck out of this car. It's a '92 2WD 5-spd Geo Tracker, and I am continually impressed about how simple (although sometimes cheesy) the car is..... I love it.

 

[DrEntropy]

They are a bit of a 'tin box' but I agree: gotta hand it to the Japanese (grudgingly /bcforum/images/%%GRAEMLIN_URL%%/wink.gif ), they've made great advances with regard to reliability... your current experience notwithstanding.

 

[eschneider]

Just an update.....

Turned out to be the head gasket. Very weird. Never seen one go to zero comression before.

FWIW, Suzuki makes a great engine. 200K miles of shameless abuse, and the cylinders looked PERFECT. Not even a ridge. Easy to fix and work on, and parts were cheap.

Thanks for the thoughts everybody....