I bought and fd about a week ago, not running with a (probably) blown apex seal. I wanted to verify that it really was a blown seal before I replaced the engine. It has spark, the fuel pump works, I checked the compression with my tester and got zero compression in all 3 chambers on both rotors. Not even a tiny little blip. (yes, I removed the schrader valve to see all 3 faces) I figured my tester wasn't working, so I borrowed a compression tester from a shop, and got the same results.

I was wondering if anyone has ever seen ZERO compression all around?

I've never had the opportunity to work on a rotary, but have done plenty of reading, and I can't see how I could have gotton those readings both times.

-Shane

 

You can have an engine with zero compression. Seals coming loose & gouging up both housings could do it.

You can also do a quick and dirty compression test by ear. Remove a trailing spark plug, and turn the engine over. Leave the plug hole open. If there is no "chug" sound as the apex seals pass the opening, there's no compression.

 

When an apex seal goes, esp a stock Mazda seal, it will tend to take the rest of the seals with it. Usually this is just a chunk or two and the rotors will still have some compression, but not always. having it happen on two rotors though is kind of odd. Thinking out loud a serious overheat might cause that, or having both plugs out of the housings when doing the test.
Just out of curiousity (and you may not know or have been told the truth, so no biggie if you dont know) but:

What do you know of the history of the car?
Has the engine been rebuilt? If so by whom?
Stock radiator?
signs of overheat?
Ran fine until ______?
Single turbo?
Signs of a single turbo converted back to stock twins for sale? Look for scratches on the shock tower, hand prints all over the intake/boost plumbing, mismatched clamps, bolts, etc on oil/water lines etc. Also look for cut fuel lines etc. indicating that a fuel system was on the car then removed.
Stock ECU?
Single or stock twins?

EDIT- also make sure that the set of plugs you are NOT removing from the engine are tight when doing the comp test, the battery is on a charger, and the TB is WIDE OPEN. These things really effect the test results.

 

+1
yes. i bought an REW back in '06 and it sat in my garage for years, untouched. i bought it knowing that it needed a rebuild, and it had one very weak pulse on each rotor. i could see that the apex seals were all intact, so i knew something else had to be at work. i finally had a reason to pull it apart a couple months ago and what i found leads me to believe it was probably overheated - the side seals were pretty much all stuck, there was a varnish/residue on all the front cover components, etc.

 

To answer your questions:

What do you know of the history of the car?
-the guy I bought if from was the second owner, and was more interested in its looks than preformance, however took care of regular maintnance. (well, he had regular maintnace taken care of)
Has the engine been rebuilt? If so by whom?
-Not to my knowledge
Stock radiator?
-Yes
signs of overheat?
-No
Ran fine until ______?
-2 weeks ago, story is he was pulling away from a red light (calmly) and it bucked like he had stalled it out. he got it to start, drove it 2 blocks (running poorly) it died again, and he could not get it started again.
Single turbo?
-Yes
Signs of a single turbo converted back to stock twins for sale? Look for scratches on the shock tower, hand prints all over the intake/boost plumbing, mismatched clamps, bolts, etc on oil/water lines etc. Also look for cut fuel lines etc. indicating that a fuel system was on the car then removed.
-everything (other than vacuum lines) appears stock. I can't see any reason to believe that its ever been modified more than it is now.
Stock ECU?
-Yes
Single or stock twins?
-Stock twins

The other (leading) plugs were tight, TB was wide open, car was hooked up to my (running) r32. It was cold, but thats hard to change considering it doesn't run.

I'm looking for another engine now, as soon as I swap it out I'll tear it apart and let you guys know what happened.

thanks for the replies,
-Shane

 

Single Turbo, Stock ECU?

-Geoff

 

so you bought it a week after it quit? were you there to confirm he was not beating the snot out of it? i ask simply because i hold this account suspect.

while this account does not explain your not having compression, it does open up other possibilities. even in cases where i've seen people have huge blow-ups, the majority of the ones i've heard will idle - albeit shitty.

come to think of it, i suppose one scenario that fits everything you've said though might be if the engine ingested some kind of foreign bodies to wreak all hell in it while he was driving.

i'd say pull the turbos and have a look inside through the exhaust ports, before taking the whole engine out.

 

Just noticed you were in Japan, so sourcing an engine should not be much of an issue.

 

Stock Twins, Stock ECU. I have no way to prove/disprove the story I was given. I do plan on pulling the turbos off to see if maybe the seals are just stuck with alot of carbon buildup, as I honestly suspect the previous owner didn't drive it very hard.

Sourcing an engine here isn't too bad, they average about $500US too.
I'll keep this updated.

Thanks for the replys,
-Shane

 

I tried some power steerin fluid in the chambers to see if I could free up some carbon and get some compression, it worked a little bit. I didn't let it sit for much time, I just worked it around good in all the chambers. Hooked the tester back up and got about 30psi in one (only one) of the front chambers, and about 10 psi in the strongest of the rear chambers.

After that I put about 1-2oz of atf in each chamber and worked it around really good. I used about half a qt total. That was on Sunday, on Wednesday I'll test compression again and see what happened.

-Shane

 

After sitting for a week with ATF in it, it squeesed out 90/20/15psi for the front rotor, and ~10/~0/~0psi for the rear rotor. So, out it comes.

I struck gold and was able to strip another FD that was going to the crusher. So that "block" will go in and I'll tear this one apart to see what the damage is.

-Shane