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Compression tester....

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Old 10-19-2003, 10:00 AM
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Default Compression tester....

So lets say I go out and buy a compresion tester....how exactly would I preform the compression test? I know I would remove one plug at a time and have to remove the other coils, but do I have to do anything with fuel? Then just crank the car, correct?
Old 10-19-2003, 10:05 AM
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Default Best way to do this test it to

1. Pull all the plugs and coils
2. dont have to do anything with the fuel
3. just crank for a few seconds, set the gauge so you can watch it while you crank and stop when the gauge stops moving
4. just make sure you do it exactly the same for each cylinder
5. should come out with 175-185 lbs if the compression is perfect
Old 10-19-2003, 10:44 AM
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Default Thanks!

Doesnt sound bad at all.
Old 10-19-2003, 12:29 PM
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Default Ive never done it on my A4 but...

On the last car I did a compressions test on, by the time that I got to the last cylinder, the battery had lost some of its power. This slightly altered the results, the last two cylinders we tested were lower than the first two. If you can, jump the car or hook it up to a battery charger while you run the tests.
Old 10-19-2003, 05:10 PM
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Default contrary to what he says...I'd pull the fuel injector connectors

you'll set a code in the ECU, but just clear it when you're done. that way you don't have a potential fire hazard or flooded cylinders.

Also, you definitely want to hook a running car's battery up to yours with jumper cables so you don't lose juice as you go. I found that out the hard way when I did my test. Thought my engine was f'd. hooked up a running car and bam, all cylinders within a percent or two.
Old 10-20-2003, 09:01 AM
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Default I agree with steve here....I unplug the injector connectors too...

I also have somebody else do the cranking while I watch the gauge.
Old 10-20-2003, 10:26 AM
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Default There is not much fuel being put in the motor if the maf sensor does not read any air

being sucked in.
Old 10-20-2003, 10:56 AM
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Default any amount is too much when you're pulling plugs

why take the chance on a spark somewhere as you pull the plug and release a flammable gas into the engine bay?

takes 15 f'n seconds to pull the connectors. and a minute to clear the code.

work safe. keep your hair and your fingers.
Old 10-20-2003, 11:40 AM
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Default I have done it a bunch of times on my car and others

and have not yet even came close to smelling gas and I know exactly what gas smells like since I used to pull switch injectors and FPR right in the pits at the drags.
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