I recently notice my mark was getting sluggish so i did the normal tune up and air filter and oil change cause it needed it. But did not help much also my gas milege went from 17 to 12 and my oil smeels like gas and is water thin. So i did a compresion test and got 115-117 across all 8 Anyone know what a typical motor should have for compresion numbers. Any ideas guys thanks.
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Time To Rebuild?
- Thread starter 91lsc5spd
- Start date
Gray Mist
Active LVC Member
compression...
115- 117 is acceptable, though a bit on the low side, most inportant is that they are all close to the same. If I remember correctly 135 lbs or so is more disirable. Sounds like engine may be getting tired. (I'm sure if I'm wrong I'll get pounced on rapidly.) The fuel in the oil isn't helping to protect the rings for wear.
Sounds more like a fuel problem. Gas smell in the oil and very thin oil are not a good sign. Diluted oil is not the best lubricant for engine parts. But it will clean the inside of the motor! The fuel getting into the oil is usually associated with flooding problems and raw fuel drains past the rings.
I would think a fuel pressure test with leak down would be in order. To do this, hook up a fuel pressure guage and check pressure at idle and under load, then shut engine off and see how fast the fuel pressure drops. If injectors or back pressure valve are leaking, the pressure will drop accordingly.
If its injectors, raw fuel will drain into cylinders and past rings diluting the oil.
If it's the back pressure valve it would show up as a little bit more cranking before engine starts.
115- 117 is acceptable, though a bit on the low side, most inportant is that they are all close to the same. If I remember correctly 135 lbs or so is more disirable. Sounds like engine may be getting tired. (I'm sure if I'm wrong I'll get pounced on rapidly.) The fuel in the oil isn't helping to protect the rings for wear.
Sounds more like a fuel problem. Gas smell in the oil and very thin oil are not a good sign. Diluted oil is not the best lubricant for engine parts. But it will clean the inside of the motor! The fuel getting into the oil is usually associated with flooding problems and raw fuel drains past the rings.
I would think a fuel pressure test with leak down would be in order. To do this, hook up a fuel pressure guage and check pressure at idle and under load, then shut engine off and see how fast the fuel pressure drops. If injectors or back pressure valve are leaking, the pressure will drop accordingly.
If its injectors, raw fuel will drain into cylinders and past rings diluting the oil.
If it's the back pressure valve it would show up as a little bit more cranking before engine starts.