Piston compression tester

Front rotor:

40psi bounces, build up was 105-110


Rear rotor

Not much, build up was less than 30psi, and bounces were uneven and didn't even clear 10-12psi when the needle did bounce.

That sure was alot of hard work only to find out that my motor was garbage.

 

Okay, feel better now and i haven't cried for couple hours.

I think Im going to take a short break from anything rx7 related for a week or two (or atleast try, going to be hard!!! ), then hammer down on pulling the motor and doing an ls swap....ah no, **** that just kidding Anyway, get the iron off to see what's up with that rear rotor the end of the month. My nerves are shot and I could use a couple beers and some fishing over the next couple weekends. Plus I can't move my hands in a normal fashion with all the knuckle busting going on lately.

"I'll be back."

 

How'd she blow?

 

This is a newly rebuilt motor that I couldn't get started so 0 miles, so something wasn't right on the rear rotor. Stuck seals, something slid out of place, etc. Find out when I get in there.

Too bad because that front rotor was holding some major psi for being cold and not broke in. But I only have to rip off the rear iron. got someone local to help me look into it so we will see.

 

Brand new engine and the rear rotor isn't making any compression? Refund from whoever you got it from!

 

What is buildup? You let the pressure build up in the gauge while cranking the engine? That's a meaningless bit of information in a rotary engine. Have a proper test done with a "real" rotary-engine compression tester before you freak. If you lived closer to PA I would do it for you gratis.

If you live close to Gold Hill, I may be able to arrange a proper test. In that case, PM me.

 

I used the guidelines from Kevin's site for using a piston compression tester so even though it isn't the best way to test for compression, it's better than nothing.

It was built by me with help from someone who used to live around here. I can't hold him responsible and it hasn't even crossed my mind to, because the guy was nice enough to help me out in his free time and didn't charge me anything and he had done this successfully many times before for himself and other local club members, so I'm sure that whatever is wrong isn't something done out of lack of knowledge on his part, maybe something slide out of place during assembly and went unnoticed at the time, etc.

I'm going to just pull a lower plug at a time and have someone crank on it so I can listen to the pulses on the rear to see if it will give me an idea of whether its an apex seal or a side seal.

 

Now I'm not entirely convinced it's the motor. I did another test, just with the lower plug holes opened and felt with my hand while someone cranked on it, had a good rythmic ch-ch-ch-ch-ch-ch and I there might have been slightly more coming from the front rotor, but after checking back and forth for 10 seconds, if there was, it was hardly noticeable. I thnk somebody MIGHT have had the tester hooked up wrong (me).

Replace trigger wheel, spark plugs (sat in the shed for 2 years but are new....never know) and take my injectors out and again, they were cleaned and flow tested but maybe I have a stuck injector. The rear plug smelled of fuel noticeably more than the front plug. This while give me a chance to go back to 550 primaries and with the steve kan tune and same mods on the car other than smic, if everything is in order I should be able to get it started.

Maybe it's just wishful thinking though.

 

u do have the throttle open the whole way when your testing right?

 

Yes.

I've had a couple people that think it's just flooded bad.

 

are you sure you're screwing in the compression tester all the way? You stated that this was a new build. Did you double check that the seals are lubed up? Pour a little bit of oil / marvel mystery oil / seafoam down into the rotor housings. Leave the spark plugs out and hand crank the motor a few revolutions to lubricate the inner walls of the housings. After a few revolutions, the majority of the oil or seafoam should be expelled through the spark plug holes or the exhaust manifold. Be sure to put a rag nearby the spark plug holes or you'll have a mess. Then proceed to crank the motor a few times, with the fuel pump relay, and ignition disconnected. Now try hooking up the compression tester and see if your pressure numbers are up. It may or may not help break loose the stuck seals. Just a suggestion before you go through the pain of breaking the motor apart again.

 

I'm going to disable the fuel tomorrow and give it a little spray of starting fluid to see if the engine will react to it.