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Mini Compression Test


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#1 Moggyman60

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Posted 12 October 2019 - 12:54 PM

Hi everyone, can anyone help with a compression test i am trying to do on my 998 mini cooper?

i have taken the power feed off the fuel pump and removed the plugs and on cranking the engine just flicks up and down

with the engine cranking over but when you stop instead of getting a reading the dial stays on zero, is my compression

tool faulty or am i doing something wrong?

Cheers Andy :shy:



#2 Ethel

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Posted 12 October 2019 - 12:58 PM

Most gauges do have a lock feature to trap the highest figure. If yours does there'll be a release button to zero it again. Have a look if there is a button maybe it's stuck?

 

 

 

....just a thunk: If there isn't a lock but it appears to be reading, you could try filming it with your phone to capture the highest figure the needle hits.



#3 Moggyman60

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Posted 12 October 2019 - 01:22 PM

What about if i try with the other spark plugs in place?



#4 Ethel

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Posted 12 October 2019 - 01:28 PM

The plugs make no difference other than making it harder to turn over. It could be a major fault like a burnt valve or holed piston - try testing the other cylinders you'd be very unlucky to have suffed them all. Can you see the rockers moving through the oil filler hole?



#5 dyshipfakta

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Posted 12 October 2019 - 02:28 PM

Faulty gauge or you are using it wrong. You only get compression the point where the needle is high is your compression.

#6 Rorf

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Posted 13 October 2019 - 05:05 AM

Thousands of youtube videos on the net showing how to do it correctly :D



#7 Moke Spider

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Posted 13 October 2019 - 06:37 AM

There's usually a Schrader Valve in them, same as used in your wheels. Yours has perished or is missing.



#8 sid trunley

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Posted 13 October 2019 - 06:12 PM

is it a screw in tester or one that as the rubber at the end I find it easier if there is two people doing it one in the car to turn the engine over take the HT lead off sid






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