Lame'O compression test question......?

[Halon]

I've always done mine with the throttle plate all the way open. Never really dug into the 'why' aspect, just did it like that because that's how I learned to do it. Whatever way you do it, I'd say just be consistent across the board. Don't do 2 cylinders one way, and the other 2 the other, or one month do it one way, and a couple months later change your method. Just be consistent is what I'd say.

As for only having 20 on the first crank and then jumping up, well the only thing I can think of is, maybe the piston was already like 3/4 of the way up when you started the test, so there for the first crank only gave a little bit of pressure compared to the other which maybe had a full crank in on the first 'pop'. I've never really payed much attention to the psi number on the very first crank, because I'm usally by myself, and so I'm just sitting in the car, cranking it over a few times, then get out and see what the gauge is at.