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Proper Grounding for Compression

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Kjay

Member
While reading one of the post on compession I noticed you should ground the coil leads and ecu. What is the best method to accomplish this grounding?
 
I leave the spark plugs attached to the wires and let the threaded part of the plug rest on the cylinder head.
kemo
 
kemo said:
I leave the spark plugs attached to the wires and let the threaded part of the plug rest on the cylinder head.
kemo
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This is good and you can use a jumper wire with alligator clips to make a better ground, attach one clip to the ground on the plug and the other clip to a case bolt:s
 
Help a novice out and help me understand how grounding will change the compression. I'm not doubting that it the proper procedure but would like to understand how it makes any difference. Thanks.
 
glenalt said:
Help a novice out and help me understand how grounding will change the compression. I'm not doubting that it the proper procedure but would like to understand how it makes any difference. Thanks.
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It's a precaution taken during a compression TEST. Grounding the secondary of the coil pack eliminates the tremendous stress put on the secondary insulation within the coil assembly.

In other words never just pull the wires off the plugs and let them hang while you crank the engine during the test.

The ECM ground part I am waiting for an answer to.:p
 
Here is how I bypass all concerns with grounding anything while doing a compression test. Remove the plugs, install compression gauge. Leave ignition off and kill switch off. Using a jumper wire or a remote start button, jump from the terminal that the green wire at the starter has been removed from, to the main battery cable on top of the starter there by spinning the engine over without the ignition on at all.
Anyone see a problem doing it this way?:31:
 
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