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Compression Test


91GranSport

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How do you use a compression tester? From what I understand you remove one spark plug and thread the compression tester into the spark plug hole. Then you start your car. Obviously you only do this one cylinder at a time. However, do you leave the car running do you simply start it up long enough to complete one cycle then shut it off? Thanks.

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That's basically it, BUT make sure you unhook the ignition system so the car doesn't actually start (Just pull the ignition fuse). Pull one plug at a time, screw in the compression tester, and then crank the car about 5 or six times. Get out and read the gauge, relieve the pressure off the gauge then remove it. Then put the spark plug back in and go to the next.

 

That's how I've always done it......It may not be the 100 percent correct way, but it seems to work for me.

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I'd recommend using a remote starter switch ($10-$15). That way you will be in front of the car and watch the needle fluctuation and not just the end of the needle movement after you finish cranking but the whole activity of the needle from start to finish.

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Thanks for the help guys, that's great! By the way, where the hell is the ignition fuse? I've been looking for it! Is it in the engine bay or in the glove compartment?

 

I have a '91 Regal GS sedan where the fuses can be located either in the glove compartment or under the hood on the passenger-side. Thanks again!

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my friend, its in the engine compartment, you can also take out the fuel pump relay, located near the batery, monted on the strut tower, says fuel pumpo relay on the lid

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Damn, if I knew here the fuel pump relay was it would've been easier for me when I changed my fuel filter two years back! Thanks again for the help guys!

 

my friend, its in the engine compartment, you can also take out the fuel pump relay, located near the batery, monted on the strut tower, says fuel pumpo relay on the lid
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Damn, if I knew here the fuel pump relay was it would've been easier for me when I changed my fuel filter two years back! Thanks again for the help guys!

 

That won't help you. Just pull the ECM fuse INSIDE the glovebox. That controls ignition power to the ECM and will NOT erase the ECM.

 

If you pull the fuel pump relay, the car will still start provided you have sufficient oil pressure. The fuel pump relay is just a backup to the fuel pump switch inside the oil pressure sensor.

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No, because diesel engines run at around 20.5:1 compression and they don't use spark plugs to ignite the fuel. The compression itself builds until the fuel is ignited due to the extreme force being put on it.

 

I would assume the "compression tester for gasoline engine" are the same for all gasoline engines and would not work on a diesel engine.
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