manual compression checking
 

i live in the middle of the north pole and my nearest mazda dealer is 3hrs away. im trying to get some thing str8 and i have never gotten an answer... when u do a manual compression check (u know, the whole putting ur finger in the hole while a buddy cranks it, ok that just sounds wrong) but what are you really looking for?? blowing or sucking?? ok, that sounds really bad! no wonder i couldnt find nothing in the search... theres no cool way to ask this...

HAHAHAHAHAHAH LOL

If you feel some blowing while you put the finger in the hole and your friend cranks you'll be all good...

Sparkplugs are on the compression side of the engine so you should feel the pressure coming out.

I'd just go down to Autozone or something and spend $30 on a compression tester. Remove the trailing plugs, disable spark and fuel, screw it in, and see what you get.

Dale

Remember to remove the one-way valve in the compression tester, that way you will ba able to see the compression on all the faces of the rotor.

Are yall talking about using piston compression tester on a rotary ? Do the numbers come out a lil different ?

anybody???

sooo... no sucking???? at all?? the guy that had the car before said u need both... but every time a thread drifts off in to the compression cheking thing... someone says air coming out, some say sucking and blowing and no one clears it up.... this time id be me, making sure...

You're going to get both- as the apex passes the hole, you will get vacuum also until the next face pressurizes it. The blowing should be much sronger than the sucking (man, you are right- this is hard to say and be serious lol). Best way is still with a compression gauge though. Like someone said, just use a standard gauge but remove the schrader valve from end of the hose for it (same as a tire valve). It will not build up to max comression like you would want on a piston, but it will jump up and down as each face passes. I forget what is good- others can be of more help here. If you see something like 80-80-20, 80-80-20- then you're screwed :). Hope this helps some.
Joe

The compression gauge I use is for a piston engine of course, but it has a relief valve on the side. Screw in the compression tester, hold down the relief valve, crank the engine, and watch the pulses. I then let go of the release valve, and see what pressure it builds up to. If you see 3 even pulses and over 90-100 psi built-up compression, that rotor's fine.

No need to remove the schraeder valve from the tester, BTW.

Dale

You are better off watching the pulse of each face, not the total compression. To do so would require removing the schraeder valve. Unless you have a good eye and watch the increments as it jumps to make sure it is jumping evenly with each pulse- but it is easier to remove the schraeder and just focus on one part of the gauge instead of trying to watch it climb evenly- no?
Joe

Really, I just use both readings - the pulses with the relief held in, and the total build up. The pulses lets you know if the side, corner, and apex seals are intact and doing their job, and the buildup number shows the general "tightness" of the motor.

Not to mention I can still use the tester on a piston engined car if I need to :).

Actually, I've gotten to where I rarely use it. I can tell a lot about the health of an engine just by listening to it start and idle. That's just from being around too damn many RX-7's :).

Dale

Gotcha, I just wanted to keep it simple for someone who may not be too familiar with how the gauge works, reads, etc. plus you have a bleed off on yours- some don't. Lol, I hear ya about too much time around them- I am the same way with DSM's- I can tell a lot just by hearing it crank...
Joe