"Greg;
You should get some br
"Greg;
You should get some brief instructions with your tester, but you will need to set each cylinder at TDC on compression stroke and HOLD IT THERE, using a long socket bar. 18" or longer is best, using the damper pulley nut to turn it over and hold it.
With the engine warm, and the plugs out, start with #1 using the TDC timing mark on the damper. Go in 1/4 turn increments using 1-8-4-3-etc until you get to the cylinder you need to test. Your 1st test will be either TDC on firing stroke, or just as exhaust is closing and intake is opening. If the latter, the cylinder won't hold air pressure. Turn the crank 1 more full turn to get to TDC firing.
Note that this works best with two people; one dedicated to turning the crankshaft and HOLDING the cylinder to be tested at TDC, while the other applies the air and takes readings.
If the cylinder being tested is even slightly off TDC, it will want to rotate immediately to BDC as soon as you put air to the cylinder, so you need to be ready for this and hold the socket bar tight! Note also that it helps to mark the damper pulley in 1/4 turn increments with chalk or a white marker to make alignment of each subsequent cylinder easier.
Alternatively, you can feel each piston approaching TDC by inserting the eraser end of a pencil into the plug hole, angled down slightly. With your helper turning the crankshaft slowly, when the piston just stops rising, that's TDC.
Leakdown testers were originally used for checking piston aircraft engines, where one person holds the prop blade at TDC, and the other does the test. Holding the end of a prop blade sounds scary but it isn't. It's much easier than holding a V-8 engine crankshaft, because the prop blade is quite long, and provides more moment arm to hold the torque.
Good luck,
Rod"