How to conduct a compression test...

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Originally Posted by e34.535i.sport

Thanks Dave...

What I'm wondering is when I crank it there's still going to be sparks going to the leads, which could be dangerous?!

Could I do it by using the CODE function on the OBC - as this allows it to crank but not start?! Does the CODE function stop the sparks/fuel or something else?

I worry too much I'm sure.

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Pull your fuel and DME relays.

Dave

This might help. They are located under the black cover just rear of the pass. side strut mount.

http://img.photobucket.com/albums/v1...p/DSC00502.jpg

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Originally Posted by e34.535i.sport

Brilliant! Many thanks for going to that effort for me Dave... So pull the white one, the blue fuse thing and the Lead going from the distributer to the cap and bang the compression guage in! Will do tomorrow hopefully and report back with some big numbers hopefully!

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The pic is from a fuel pump test. You ill not find the blue fuse thing . You will, however, find the fuel pump relay in that spot, which you will remove for the comp. test.

Best of luck,

Dave

Have you done it? How did you get on?

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Originally Posted by whiskychaser

Engine may make a sort of 'bloop bloop' sort of noise. Dont worry - its only blowing air out of the other plug holes:)

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Thanks Whiskey... I'll be prepared for that then. I hope this is one of them things I get nervous over and then find out its a peice of piss. I suppose I should be worrying more over the results than the test itself!

No been in work but heading home now... Lets see what happens!

Just so I've got this straight I'll do it with no sparks in - should I expect air to come out of the other cylinders or anything else that may seem unnerving?!

Quote:

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Originally Posted by e34.535i.sport

Just so I've got this straight I'll do it with no sparks in - should I expect air to come out of the other cylinders or anything else that may seem unnerving?!

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Engine may make a sort of 'bloop bloop' sort of noise. Dont worry - its only blowing air out of the other plug holes:)

you should try a differential compression test

Hey guys results are as follows... Not sure whether I should have been measuring the highest point the needle reached whilst in motion or the point where the needle settled after the seven cranks I did - so here's both figures:

HIGHEST POINT REACHED (psi)
#1 - 180
#2 - 180
#3 - 190
#4 - 190
#5 - 186
#6 - 186

SETTLED VALUE AFTER SEVEN CRANKS (psi)
#1 - 173
#2 - 173
#3 - 181
#4 - 186
#5 - 180
#6 - 182

I don't know which is the correct set of values but by my reckoning there is only a 6.99% error on the settled value and only slightly higher on the other which is good I hope?!

One thing though, as I conducted the test, and removed the key after each set of crankings the words OIL PRESS SENSOR came up on the dash... It didn't come on after I removed the guage but then when I done another set of readings it would chime again... Please tell me this is normal or nothing to stress over so I can stop worrying about it. :(

Overall I feel a bit more secure over the engine health as the values seem ok as far as I know (which isn't normally much) and that I didn't damage the HG when it overheated a couple of weeks ago...