compression test video, what do you see?
 

OK guys, i have been struggling with getting a car to start that doesn't want to. My last resort was compression so i decided to try to take the compression. It is the first time i try that and i have to say i don't like what i see but since it's the first time, i would like to know what you guys think of it.

first of all, i unplugged the coils harness and removed the circuit relay (so the fuel pump doesn't run and the plugs don't fire). I removed both leading plugs and left the trailing in place.

This mean that in the first vid, what you see on the gauge is the compression of the first rotor. To me it seems like one doesn't look to be working but what do you think? Also, the sound you ear is of the rear rotor on (since spark plug is out)which it really looks like one of the apex seal isn't doing it's job. You can ear only 3 "whoosh"

on the second vid, the gauge is of the rear rotor and it really doesn't go high. You can ear the three "whoosh" of the front rotor i beleive.

please let me know what you guys think.

thanks a lot

puma

http://media.putfile.com/first-rotor-compression

http://media.putfile.com/rear-rotor-compression-74

I'm no expert, but it would be really helpful if you slowed the video down, or used a site that will let us download the video and edit it ourselves.

For instance:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/compression-test-video-443006/

-s-

hmm do you have any site where i could do that?

That doesn't look good on the rear rotor.

IME, the exact numbers you get using this method aren't accurate, but you should be getting nice even bounces.

I guess it's shot, but since I'm not an expert I'd take it to a shop for a 'real' compression test first.

Dave

The rear rotor definitely has a seal gone (or stuck).

The vid of the front rotor is hard to tell but it doesn't appear to be very even either, it's just not near as bad as the rear.

is the fact that i removed the spark plug in the other rotor a bad idea?

yeah that's wht i thought

Here is a link to someone's video of a compression test on a blown motor. Both rotors are bad.
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/compression-vids-308325/

-s-

someone was able to edit the vid and put it in slow motion, here it is

front rotor

Click here to watch slow-front-rotor

rear rotor

Click here to watch rear-rotor-slow

Both look bad from the slow-motion videos you posted.

Front looked like:
85-85-50

Rear:
30-30-10

Note that I've never rebuilt a rotary myself, so I'm just repeating info that I've come across in my own research. From what I've heard, a single low pulse indicates a failed side seal, while two low pulses indicate an apex seal. Someone please correct me if I'm wrong.

-s-

Does the car start with compression like that???

no the car doesn't start, this is why i did a compression test

this is correct

Im no expert but what I see is a blown motor...

OT but heres a computer lesson for you guys...
You can get anything off a webpage with a little know how....putfile is super easy!
If you want to download a video from putfile all you have to do is go to view, then source. This will take you to the raw HTML of the page, all you have to do is find out the link the video sits at, I know that putfile normally uses AVI, so just search for that in the source code, bam theres your link.

IE: Heres the first videos actual link
http://uploadfile.putfile.com/videos/24811091711.avi

Different webpages or videos may be in different formats so it may take some searching, but its always possible if the video is playing from WMP....capturing videos in a flash player is a little more tricky.

Does anyone think that it might be carbon build up or something?

I'm the owner of the motor, and this thing was runing good before I swaped from auto to manual. The motor has been stopped since October and has not run since then. Is it possible that a seal decided to stick or glue itself on the housing and broke when we tried starting it without any oil in the housings?

This is simple. The rear rotor is bad, at least 1 apex seal is bad and it really doesn't matter what else is going on. The engine needs to be torn down. No question, no excuses, just do it!

I had a motor with the same compression behavior, but a little better on the back rotor. It had hard starting and I eventually rebuilt.

I think the problem is this. You can have all the seals in tact, but the carbon that gets in the grooves of the side seals and behind the corner seals disallows the seal to move freely, and thus seal adequately. Other than trying to free those seals up, a rebuild may be the only option.

Thanks a ton. It's been years since I've used looked at a webpage's source code, I had completely forgot about that.

-s-

so anyone think it can be seals that are stuck? what do you do to free them up?

PUMA...here is what is up with mine....

My car started and seemed to drive relatively fine at all speeds. I couldn't boost past 7 psi though. Car idled like absolute JUNK...up and down back and forth. Here was my quick run down for compression:

Rear: 90-90-90
Front: 40-40-90

I know that either one of my apex seals is blown or stuck on the front rotor...I just can't figure out why the car still drove fairly well apart from the boost and 3k hesitation. Is this possibnle because I had one good, consistant rotor at 90's on all 3 hits? Either way, the motor and tranny are rady to be pulled out (need to replace 2nd synchro as well) so I am HOPING that is it stuck and I can keep my housings:) They are ported and it would be nice not having to get another housing and have to try and port match it to the rear.

Trev

I see uneven bounces on both front and rear, so I think you have stuck or cracked seals on both sides. Either way, it needs to come apart, and won't fix itself. The exact internal problem is a moot point, kinda like "why" is a tire flat...it doesnt matter why, you still need a new tire. You'll find out when it comes apart.

all right, thanks everyone for the help.

anyone think that the fact it was made when the engine is cold could affect a lot the test?

you'll just get inaccurate readings (higher than normal).

Hi Puma, on my 20b with cold engine i have about 118/ 120Lbs with street port.
Your engine is dead.

higher? damn i don't want to see what they are when the engine is hot :D