How to tell if I'm on compression stroke

[timebombprod]

How do I know.if I'm on compression stroke to do a leakdown test?

[Guest]

Maybe remove a spark plug and turn the engine until you feel air coming out?

[timebombprod]

Maybe remove a spark plug and turn the engine until you feel air coming out?

Maybe? Hmmmm

[Burque73]

How about inserting a wooden dowell in the spark plug hole and watch it while rotating the crank. Or just get a flashlight and look inside

[rphillips]

How about installing the gauge, pressure will build on compression stroke, not on ex. stroke

[Brendan W]

If the valve cover is off you can tell by what the inlet cam is doing.
Down and back up is the tell for the start of a compression stroke.

[Guest]

How about inserting a wooden dowell in the spark plug hole and watch it while rotating the crank. Or just get a flashlight and look inside

That will get you TDC, but unless you watch the valves, you won't know if it was the compression or exhaust stroke.

[Grimly]

That will get you TDC, but unless you watch the valves, you won't know if it was the compression or exhaust stroke.

Put your thumb over the plug hole.

[Burque73]

That will get you TDC, but unless you watch the valves, you won't know if it was the compression or exhaust stroke.

Gotcha....

[Guest]

Put your thumb over the plug hole.

Since that response was related to using a dowel to visualize the movement, it would be just a wee bit ... difficult to put your thumb over the hole.

[Killer2600]

Great methods given but I'm going to go at this another way. You're doing a cylinder leakdown test, so set the piston at TDC and run your test. If you get leakage rotate the crank 360? and run the test again. The test that leaked less is/was your TDC compression stroke.

[Guest]

Or, ... if you simply look through the spark plug hole before screwing in the gauge, you can see the valves to tell whether they are open or not.