OK,I gotta do a comp. test,but I cant find a comp. tester specific for the rotary.Does anyone know where I can get one? Would strauss,pep boys,or any other large "chain" store carry them? Or should i get a "normal" one and modify it?If so which one can I modify? Also I was wondering,is the compression measured in p.s.i. ,or another form of measurement? If it IS in p.s.i., I can just make a tester from some old oil burner parts I have and 200 p.s.i. "wet" gauge.

THANX IN ADVANCE,...

ALSO,IF MY IDEA WONT WORK,...TELL ME WHY,AND WHAT I NEED TO MAKE IT WORK.

 

I believe a normal compression tester can be used, but the Shrader valve has to be removed in order for it to work on a rotary.

 

yup, I got one, I haven't figured out how to access the schroeder valve yet, but all you have to do is yank that sucker out, and watch it go to three distinct compression cycles..

 

The schrader valve is in the very bottom (tip) of most gauges. It can be removed with a tire valve cap that has the slotted head. If you don't have a cap like this any place that services tires will have a valve wrench to remove it.

Disconnect the main fuse to disable the injectors. Either block the accelerator open or have someone hold it to the floor while you are cranking the engine over. You will be looking for three bumps in the gauge reading. This indicates all three apex seals are OK. If one seal is bad you will only get one bump because one seal affects two chambers. If two seals are bad you will get no reading, or at most a very few pounds.

On a good engine you need to see each bump at or near 80 PSI. After checking for the three bumps install the schrader valve and get a max reading by turning the engine over for several copmression cycles. You should see near 110 PSI or more on a good engine.

 

So what exactly does the schrader valve do that I gotta take it out,then put it back in,hold the highest reading or something?? You guys got me confused,cuz all of you said it has to come out,but only 1 said it had to go back!!

 

Removing the Shrader valve lets the needle bounce and give you three readings for the compression of each rotor face, hopefully near 80-80-80. This is the important comp test.

Putting the valve back in give you a max reading.

 

HoNdAh8rRx7LuVr, im tellin you its that damn back rotor

 

The schrader valve is just like a tire valve, it keeps air pressure from leaking out until you press the release pin in the middle. It can be unscrewed from the tip of most any inexpensive compression tester with either a pair of needle nose pliers or a tire valve remover/cap.

 

Mazda service manual says to screw the gauge into the trailing plug holes.

 

You don't have to remove the schraeder valve, just use your fingernail or a screwdriver to push the little needle in while somebody else cranks the engine. That is how I do it.

 

me too.. stupid rear rotors blowing..

 

I usually just hold the release button down. Should serve the same purpose, I'd imagine.

 

Whats good comp. for a COLD eng.?? Remember my car wont start and this is part of a LONG and AGGRIVATING process of narrowing **** down.And if I do some how manage to start it,whats the lowest acceptable reading for a WARM engine??

 

ANY HELP?!?!?!?!?!

 

Let me say right off that the following numbers are from my personal experience only. I am not trying to give you hard and fast compression numbers here. Others may have different ideas. My experience has been that an engine with a compression of 80 PSIG on each rotor face will not flood. I haven't had my car flood once since its rebuild with new rotor housings and lapped end housings.

I have found that at 60 PSIG (pounds per square inch, gauge) or below on a warm engine you are likely to experience hard starting and frequent flooding. Compression numbers above 60 PSIG are good, and 80 PSIG is near perfect. A total compression test (where you check the accumulated pressure) of 100 PSIG or less is bad. Perfect here would be 120 PSIG or better. Remember that one bad seal will affect two faces of the rotor. Two low blips and one decent blip means you have one seal (at least) stuck big time. Remember to watch for the individual blips as you crank the engine over. Make sure the accelerator is wide open here. You also need a good hot battery to spin the engine over as fast as possible. Failing to do either of these steps will result in a false reading. Another thing to remember is the need for a relatively close reading on each rotor face. A big difference will cause the engine to combust the fuel/air mixture less efficiently on the bad chambers and thereby cause excessive strain on the engine components. It will also cause accelerated wear on the rotor housings and end housings from the excess amount of fuel diluting the lubricating film of oil.

If you experience low compression (most likely will be the rear rotor) squirt a little ATF or engine oil through the spark plug hole. Recheck the compression after this. A higher reading will indicate sticking seals. The first seals to stick are the side seals on the rotor. From this you can deduce that the engine is on its way out. Performing the ATF soak might buy you some time.

If you do indeed have low compression my suggestion would be to plan on an overhaul as soon as possible. This will prevent you from ruining the rotor housing and probably the rotor as well when the apex seals take a ****. Overhauling a rotary before the housings are damaged in this fashion is mainly a clean up and new seal job. Expect to invest between 1,000 and 1,400 dollars for a decent job at this point. Waiting until your engine blows up will require a new rotor housing. These are over 400 bucks each new.

 

A stickler for details,nice. Thanx for the super informative post,thats what I needed. Well I'll either be buying or building my compression tester this week(when the got damn rain stops!!!!),I will be sure to keep u guys posted on the status of my 7. THANX AGAIN!!!!

P.s.-if anyone wants to learn how to build a compression tester,pm or im me and ill explain it.

 

hmm so just get a basic checker and check after engine has warmed up then cooled....do i pull ecu fuses?? or do i just need to remove a trailing plug and insert the checker will that work??

CB

 

well i would help but what your doing to my mom has made me mad! lol

james

 

i didnt do anything to your mom, if the herb waSnt getting to you , you could see its the post above mine:smile: