I just got through looking at a 1991 RX7 Turbo II conversion in the hopes of buying and want to verify that the procedures we used to test compression were correct.
The car would would crank but not start so we did the test with the engine cold. The compression tester was a generic piston tester purchased from Autozone so the schrader valve was removed. The EGI fuse was taken out and we tested the Leading spark plug for Rotor # 2 ( rear housing ) and Rotor # 1 ( front housing ). During each check all other spark plugs were in place and the ignition coils were off for trailing spark plugs. The Front housing had very little compression ( less than 10 psi ) while cranking. The Rear housing showed 70 plus psi while verifying each bounce in compression signaling each rotor face. Can someone verify if this is the proper way to test for compression. Thanks

 

did you floor the gas pedal while doing it? doubt that it would make up for 90PSI worth of compression but still worth asking

 

If the front had 10psi then walk away or expect a rebuild.

 

Yes, gas peddle was floored while cranking motor over for no less than 5 seconds. I thought a good compression reading for a cold engine was 60 psi and above ? As for purchasing, I decided to pass. Just wanted to make sure I was was using the correct procedures and specs when I tested.

 

I used a piston engine tester, you can test a rotary if you hold the button down. Doing this allows you to get 3 "jumps" or readings so you can test each face of the rotor. When doing the test you need to remove all of the spark plugs, leading and trailing for both housings. Put the compression tester in the bottom (leading) spark plug hole.

Once it is in, hold down the "air release" button on the tester and have someone try to start the engine.

You should get 3 little "jumps" or readings on the compression tester. Each reading, or jump, is for one face of the rotor.

Proceed this again for the rear housing.

You can also do this test on an engine that is not in a car, just crank it over by hand or with a socket, you will need some kind of power source however. Like a car battery.

 

Since you removed the valve though, you might not need to hold down the air release button. But each and every spark plug needs to be removed to prevent the engine from firing.

 

No, if you remove all of the spark plugs, there will be no compression since the air will just fly out of the open holes. Don't hold the button down either since the air will just pass through the tester without ever making it to the gauge.

You do need to remove the EGI fuse to avoid the car starting.

Yep, if you're only reading 10 on one of the rotors, that's no good. Sounds like you're doing it properly. I use the Autozone piston gauge and it's always worked as planned.

 

You did the test properly. Looks like a rebuild is in the future for you. Don't worry, rebuilding it is not hard.

 

How would I remove the Schrader valve so I can use my piston tester on my 13bt? I guess that means I got an incorrect reading.

 

Would someone please explain definitively how to test compression using a standard compression tester?!?! Styx, that means you! (Guru advice needed)

 

take the valve out of the hose at the bottom of the tester.
If you push the valve up near the gauge you can see the "bounces" and just note if there are 3 equal bounces.
If there is not then you got problems.
When you let go of the valve it will give you an overall compression reading(IE: 100psi)

I got the newfangled TR-01 tester.Now I "see all"..(you know..since I am now a "guru".........................................Gur u,
sounds like a Chinese side-dish..spare-ribs and a side of Guru..)

 

the digital gauge just gives more doubt to the overall readings.

 

Sure, I suppose I could make a quick video of it; assuming time can be found in my schedule this weekend.

You can use the schrader valve remover tool and/or use a pair of needle nose pliers (They must be small enough to go inside the fitting and grab the valve inside). It's threaded in so loosen it and remove it. Be careful not to lose the valve since it's tiny. Then on, do your compression test.

 

I have been trying to remove the Schrader valve for awhile now. I can not get it out. I have purchased multiple Schrader valve removal tool and none work. I have been able to twist the valve with pliers and with tweezers but I can't get it to come out. Any tips? It definitely had loosened but it wont come out, I have been twisting it for days