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Old 15-11-2009   #1
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How do you actually do a compression test

Hi
I have a Brava 1.2 80sx
And its been using a hell of alot of oil lately about 5 litres every 3 months.
So i was talking to a lad at work and he said to do a compression test on it and lent me his tester.
So today i went to go do the test,and on the back of the tester it said undo all spark plugs then screw tester into cylinder in rotation,then says to crank the engine with throttle open.
So i removed all plugs and screwed into the first one and as i cranked the engine(turned key for 1 second) i kept my foot on the accelerator.
The first reading was saying 4.5kg/65 psi so i reset and did it a few more times but every reading was different varying up to 7kg/100psi.
Did the same on all other plugs and exactly the same so im unsure on how to get the reading i need.
Im sure im probably doing it wrong,any ideas on what im doing wrong or maybe about what causes the engine to lose so much oil.
There is a slight smoking coming from exhaust and every now and again you can smell oil coming through the heater blower
Thanks for any help
steve
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Old 15-11-2009   #2
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Re: How do you actually do a compression test

presume your trying to diagnose possible HG failure? When you change or add oil is there any white gunk, looks like mayonaise arround the oil filler cap and in the breather pipes? if so then the gasket is kaput.

i personally wouldnt trun the engine over on the starter with no plugs in. crank it by hand and you can see how the results vary whilst your doing it. Never done a test pesonally but i''m sure there are guides on here or from google
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Old 15-11-2009   #3
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Re: How do you actually do a compression test

You need to have the engine turning over at least 5 full revolutions, 10 would be better.

Engine also needs to be warm.

Cheers

SPD
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Old 15-11-2009   #4
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Re: How do you actually do a compression test

before or whilst conducting the test?
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Old 15-11-2009   #5
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Re: How do you actually do a compression test

Engine warm before starting test.

Attach compression tester then between 5 and 10 full revolutions of the engine, using the starter motor, with foot on throttle.

There is no harm in turning over an engine without plugs, it can be beneficial after an oil change, to get pressure up before starting.

When I start my old car I leave the choke in until the oil pressure light goes out, then pull the choke out to start the car.

Trying to save whats left of the engine.

Cheers

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