Quote:
Originally Posted by Nervous
. . . 1MZ. . . . . Do I need to have timing belt installed (it is not now)?
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YES, you'll want the belt on and cam timing indexed correctly or your results will be meaningless. The valve train must be operational as measuring pressure means the valve must open and close. If they are not connected, some of valve will always be open and they won't build any compression.
As said above, disconnect the igniter or the coils. Personally, if you're checking presser because you think something is wrong, leaving the plugs in will vary the readings from cylinder to cylinder because a weak cyl will allow the engine to spin faster via the starter and raise the measured compression of the "good" cylinders making things look worse than they are.
What you're really looking for here in home use is consitency. That is, what you do today, can you repeat it 6 months from now when you compare records?
I vote, pull all plugs and make sure you have a fully charged battery. Throttle position is optional just don't change anything once you start.
If you have a compressor (canned air), blow the plug holes out after the coil packs/wires are removed but before yanking the plugs. Lay some heavy shop towels over the open cylinders to protect them as Hill mentioned is a good idea too.
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