Compression Test Results - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-06-2001, 05:32 PM Thread Starter
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Compression Test Results

My 258 likes to blow blue smoke at stop lights, sometime a whole bunch sometimes a little. The engine is supposed to have only 10K miles on it. If you number the cylinders from radiator backwards in order from 1 to 6. The number 1,2,3,6 plugs are a tan whiteish color and the 4 and 5 plugs are black. I did a compression test

DRY = 1-185 2-190 3-185 4-175 5-175 6-180
WET = 1-195 2-200 3-195 4-195 5-185 6-195

I am getting ready to install a Howell fuel injection on this motor. Do I need to rebuild the motor or head while I am doing this?


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post #2 of (permalink) Old 12-06-2001, 06:00 PM
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Re: Compression Test Results

what are those units? they seem really high. mine were around 120 psi. but the important thing is for them all to be within 10%....or so i am told.

shawn

The cup isn't half full or half empty, it's just twice the size it needs to be!!!
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post #3 of (permalink) Old 12-07-2001, 09:14 AM Thread Starter
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Re: Compression Test Results

I think these gauges are not all that accurate and they all read differently. I think you are looking for the difference between the cylinders with the same gauge not the number itself. Like my gauge might read 175 and yours might read 120 on the same cylinder.

Any ideas on what is wrong with my engine? Do I need to do a leak down test?

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post #4 of (permalink) Old 12-07-2001, 04:07 PM
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Re: Compression Test Results

they better not be that inaccurate!

shawn

The cup isn't half full or half empty, it's just twice the size it needs to be!!!
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post #5 of (permalink) Old 12-07-2001, 11:43 PM
 
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Re: Compression Test Results

Blue smoke is generally coolant leaking into the cylinders. The compression reading are definitely high, check with a known good gauge, if still that high then there is probably a carbon buildup problem, thus increasing the compression ratio, and the compression readings.
i would definitelty give the block and head a real good checkout before installing a fuel injection setup. It could just be a blown head gasket, or as bad as cracked block. How does the engine run? Strong? Weak? Sputters? The plug deposits don't sound great either.
There are a few tests, like a leak down test, that could tell you about the head gasket without disassembly, but i would definitely consider a real close look at everything before going any further. Good luck, Scott...

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post #6 of (permalink) Old 12-08-2001, 12:09 AM
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Re: Compression Test Results

I thought that blue smoke was from oil.

Could it be oil seeping in through another way?

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post #7 of (permalink) Old 12-09-2001, 03:13 PM
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Re: Compression Test Results

I also thought that oil makes blue smoke . I got beat to this post .

When it doubt , PUNCH IT !!
post #8 of (permalink) Old 12-12-2001, 03:15 PM
 
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Re: Compression Test Results

My Bad. White smoke=coolant, blue smoke=oil. Sorry. Possible oil problems in the combustion chamber: bad oil control ring, usually accompanied by bad compression rings, or, bad valve guide seals, usually show up during downhill deceleration (high vacuum), blown head gasket, likely with to neighboring cylinder plugs showing up black. i would move on to a cylinder leak down test if possible, it would at least narrow everything down for you.
Did you ever get more objective compression results? If the compression was really headed towards 200 psi, you're starting to ask alot of your head gasket, as well as eventual cracks.

Scott...

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1989 XJ: has seen every state except Hawaii

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post #9 of (permalink) Old 12-15-2001, 04:58 PM
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Re: Compression Test Results

Your compression gauge is reading high . You would have to run 100+ fuel with 190 PSI per cylinder . 150-160 PSI is the limit on 92 fuel . Check it with a hot engine and a NEW gauge . Make sure you fully open the throttle when you crank it for a reading and disconnect the coil wire .

When it doubt , PUNCH IT !!
post #10 of (permalink) Old 12-15-2001, 04:59 PM
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Re: Compression Test Results

Your compression gauge is reading high . You would have to run 100+ fuel with 190 PSI per cylinder . 150-160 PSI is the limit on 92 fuel . Check it with a hot engine and a NEW gauge . Make sure you fully open the throttle when you crank it for a reading and disconnect the coil wire .

When it doubt , PUNCH IT !!
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