Chrysler Repair: engine compression readings, chevy astro van, chevy astro

Question
I know an Astro Van is a Chevy but I need the help... I have a chevy astro van and it wont get anymore than 95lbs compression in the motor, do you know what might be wrong with it...

Answer
Hi Amy,
I don't know what the minimum compression is supposed to be so that is the first question to try to get an answer for. It depends upon the compression ratio, and how fast the engine is being cranked by the starter motor, and of course it should be measured with the engine warm, and also with all the spark plugs removed. The value of 95 is not so low in and of itself for most engines of such an age. More important is what the variation of compression reading values between the cylinders, which should be within +/-25% of oneanother. If they are then I would not worry about it. If one of the cylinders was far lower then the others then that would a reason to do a 'leak down test' of that cylinder (by adding a teaspoon of oil to the cylinder via the sparkplug hole) and then seeing whether or not that raised the reading significantly. If not, then it is probably a valve issue; if so, then it is probably a piston ring issue.
I hope this has been helpful to you.
Roland
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