How to do a compression check?

I have the compression tester, but I am wondering what special steps I need to take to test compression on a SC.

The instructions mention grounding the coil wire and disconnecting all of the spark plug wires. It also mentions holding the "throttle plates" open.

Anyone know how this translates for a CIS 911?

Thanks,

Olivier

just move all the plug wires out of the way so you don't get shocked. then do the test. the open throttle relates to carbs and MFI, that have real short intakes below throttle.

Thanks,

And all I should do to prevent starting is ground the coil wire? I don't have to cut the fuel supply as well?

Also, what is the best way to ground the coil wire safely so I don't fry anything else?

Thanks,

Olivier

Olivier,
Rather than messing with High Voltage, pull the input power connector on the CD unit. You can damage the CD unit if you crank the engine with coil and/or plug leads not firmly grounded.
And yes, pull the fuel pump relay to disable the pump. When doing your test have a helper crank the motor with throttle pressed to the floor. You are at the motor end, watching your gauge and recording the results. Don't overwork the starter; 3 to 5 seconds cranking should get you a stable reading.


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Doug
'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
members.home.net/zielke/911SC.htm

it won't start with the plug wires off.