noob question

bigal0043

bigal0043

New Member
Jun 29, 2005
813
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Plattsburgh,NY
www.mk3supra.net
alright i have never done a compression test before and was looking at them to make sure my supra is still good... i have a couple question about them
1. the tester screws into the spark plug hole on the block correct?
2. Car is off correct?
3. i was looking at this one at sears
http://www.sears.com/sr/javasr/prod...tomotive+Testing+Equipment&BV_UseBVCookie=Yes
and do i need to hook a compressor to it? how does it test compression i would assume it needs to get air from somewhere.. if it does need a compressor could you just use a bike pump?

4. can you hurt your car by doing a compression test?

5. on that one from sears it says it fits 14 and 18mm size spark plugs will that fit our cars?
please dont flame me!
 
Last edited:
Y

Yeahdoug

New Member
Jun 3, 2005
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Rochester Hills, MI
1.Pull all spark plugs.
2. Screw in compression tester. (It is recommended to do the test with the engine warm but I usually don't)
3. Have someone crank the engine over ~5 times with the throttle open. Try to observe the first reading you get and then your final number.
4. Repeat for all cylinders.

If any are low try putting a little oil in and repeat test to see if your numbers come up. Also pull the efi fuse while your doing the test.
 
bigal0043

bigal0043

New Member
Jun 29, 2005
813
0
0
Plattsburgh,NY
www.mk3supra.net
thanks yea i also when and found an article on this shown below.. is that one from sears look like a good gauge?

How To Do The Test
Run the engine until it reaches normal operating temperature. Tests done on a cold engine usually show lower readings. Remove the HT leads and take out all the spark plugs. The ignition system MUST then be disabled. If this isn't done it will continue to generate high tension voltages into the HT leads which will have nowhere to go with the plugs out. These high voltages will find another route to earth and can damage the ignition system or even the car's ECU. Unplug the low tension connections to the coil or to the distributor. If you aren't sure how to disable the ignition system on your own car then check with a dealer before you start. It is also good practise to unplug the fuel injectors or disable the fuel pump, especially on cars fitted with a catalytic convertor. This prevents unburned fuel getting into the exhaust system during the test.

Screw the gauge into cylinder 1 and rest it somewhere you can see the dial while you crank the engine. Open the throttle fully either by pressing the accelerator or wedging the linkage open under the bonnet. If the throttle isn't open then air can't get into the cylinder and the readings will be far too low. Crank the engine until the gauge stops rising and count the revolutions while you do so. It should normally take no more than 10 engine revolutions (5 compression cycles) to get a full reading. You can count the cycles by watching the gauge too - each jump of the needle is one compression stroke. Write down the final reading and also make a mental note of how quickly the gauge rose on the first few cycles. Then just repeat for the other cylinders. Make sure that each cylinder reaches its highest reading after the same number of engine revolutions. If all readings are good then the test can end there. If any cylinders are low then a "wet" test can be done. This involves squirting a few ccs of oil into the cylinder and repeating the test. The oil will help seal bad rings and increase the reading but won't affect it if the problem lies in the valves or head gasket. Copyright David Baker and Puma Race Engines
 
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