Compression test on the engine

[kthorne]

Can anyone tell me what the compression should be on the 1.3. I have ( I believe a 91) with a compression of 75 on number 1 & 4 cylinders and 105 on number 2 & 4. It would be much appreciated if somebody could give me the correct values.

[FestYboy]

that's WAY low. should be around 160-180. just for giggles though, HOW are you doing your compression test?

[kthorne]

I have a hand held tester. I remove the spark plug and insert the tester then crank the engine over. I am doing this for a favor for a friend.

[Gforcefd]

my bp was around 125 on all 4 and the mechanic said it was fine.

[FestYboy]

to do the test correctly, you have to remove all 4 plugs and have the throttle fully open for the entire test. then you have to count the number of pulses you see on the gauge and match that number for each cyl. minimum 5 pulses, max 7 pulses. numbers should be within a max of 15% from highest to lowest (ie: you lowest reading should be within 15% of your highest reading, ignore the middle 2 readings)

[WmWatt]

Sorry I can't remember what the compression should be. It's at home in the Haynes manual. It gives the compression when the engine is new and when it is worn out. I've checked the compression on my '89 a few times.

Turn the engine over until the gauge stops climbing. If it climbs fast the compression is better than if it climbs slow.

You should also do a wet compression by squirting some oil into the spark plug hole first. A big change between the wet and dry indicates worn rings, as does white exhaust smoke.

Not only does the compression on all cylinders have to be between the two numbers in the manual, but all the cylinder compressions have to be within 5% of each other. One of your cylinders is 'way out of line. One of my cylinders had lower compression. There was a buildup of carbon deposits on the exhaust valve. I was able to dissolve it by putting engine cleaner in the oil. The compression has been fine since.

[darkdan]

Check out the before and after compression numbers on this:

http://www.auto-rx.com/rms13/

[WmWatt]

The Haynes manual says standard compression is 204 psi (1412 kPA)
and minimum is 149 psi (1030 kPa) on the production 1.3 litre engine. Mine are all within 5% of 190 psi with 106k km on the carburetted engine.