never used a comp tester before!

I rented one from autozone...it came with a little screw in thingie..I screwied it into the spark plug hole..then screwed the hose into the end of that...then popped the other end of the hose into the gauge.

When I turn the engine over with someone watching the gauge..the needle doesnt move at ALL.

I have the throttle wide open too so itll suck in air, and the fuel is off..and the plug wires are off...

 

Did you follow the instructions that came with the gauge?

Some gauges have a small valve that needs to be opened. In order to get a proper reading on a rotary you need to use the leading spark plug hole and remove the Schrader valve from the gauge (or hold the pressure relief open).

 

Tried with pressure release open.

There are no instructions with an Auto Zone rental gauge lol...and that valve is integrated into the hose itself...couldnt remove it.

 

Maybe the tester is broken?

 

That was my conclusion.

Even a totally fucked up engine with no apex seals what-soever and a housing scarred to hell and back..the rotor should be moving enough air to make the needle jump to at least 10psi

 

I did a compression test today. I got 120 in the front rotor and 90 in the back rotor. I heard they can be different, but 30 psi difference seems like a lot to me. What should I do next?

 

How did you do the test? If you just used a conventional tester and let the pressure build to a single results, that doesn't provide the information you need to evaluate the health of your engine. A proper compression test needs to provide the readings for each face of each rotor and the engine cranking speed at the time of the test. This requires a special compression tester.

However, there are procedures for doing a simple ghetto test with a conventional tester, so do a search for the instructions. The specification for an S5 is a minimum of 85 psi@250 rpm and a minimum difference between rotor faces of 21 psi@250 rpm.

To answer your question, if after you do a proper test the results are close to the above spec, the engine starts and run OK, just continue to drive the car.

Edit: Here are instructions on doing a simple compression test
http://www.aaroncake.net/rx-7/blown.htm

 

Good info