hybridphil

Ok so I just did a poor man's compression test on my 87 rx7 that I thought has a blown engine and has been sitting around for the last few weeks...or months...I took out the leading spark plugs of each rotor. With the front one out I hear a steady "psst". Just like it should be. With the rear one out, it puts out no "Psst"s at all. Does that mean that all the apex seals in that rotor? Or is the rotor simply frozen in place. I'm thinking that the front rotor would be turning the eccentric shaft in turn roatating the rear rotor and the lack of "psst"s meaning it's not frozen but actually blown apex seals...but then again...I am only a rotary apprentice in training. Give me your thoughts.

eriksseven

iTrader: (6)

So the motor is in the car and you used the starter to crank the motor?

The 'psshing' should be violent and clearly even in strength and uniformity in it's timing. If it's not then there's a problem.

hybridphil

The psshing was no less than violent in the front rotor. In the rear there was no psshing at all when the motor was cranked. I know that if it's uneven then that means either a side seal or apex seal is blown depending on the pattern. But what does it mean if it doesn't pssh at all?

hybridphil

bump

eriksseven

iTrader: (6)

I might be wrong (although I would need help understanding if I were), but the design of the E-shaft would make it physically impossible that one rotor would be 'spinning' while the other was 'stuck'. So, by using this logic it's obvious that no noise=no compression.

If no-one either corrects or verifies my logic, you could remove the exhaust manifold and use a flashlight to see whether-or-not the rotor is turning... Kind of the long way, but whateva'.

Carzy Driver

go get a cheap compression tester and if you want to try the ATF trick, search that

SCCAIT7

You are correct in assuming that if one rotor is turning the other IS. NOW I would suggest getting yourself a little squirt bottle and some ATF fluid. Pull the plugs out of the rear housing and FILL it with ATF. After allowing it to sit for 15-20 minutes. Spin the engine over just enough to get the majority of the ATF out of the chamber. Then take your plugs and put them back in and try to fire it off. Keeping in mind that you have Transmission fluid in there...and your going to have to compenstate with fuel... ie...pumping...holding your foot down... Just depends on weather the seals want to come back or not... (they have mind of their own)... lol... My 88 will sometimes loose compression if I start it...back it out of the driveway to move it and shut it off before it has time to get warm and lean out....thus- washing the seals... I have used the ATF trick now 5 times and each time the engine comes back.

One thing to keep in mind...If the engine does start...get it warm...drive it if possible...let it cool and change your plugs...

Also- these engines WILL run on one rotor- If it starts and shakes...rattles and rolls... and you do not have power... you know that you are not running on both.

Good luck...

One last thing- you may have to go through the process more than once... ie..filling it up with fluid...waiting...spinning it over... if your patient...and hold your tongue right...they will come back! lol...sorry... its almost 1:40AM and I had 4 final exams today starting at 8am... Anyway.. Best of luck... Keep us posted!

KompressorLOgic

iTrader: (6)

if your getting nothing out the back at all then somethings toast, you dont get more hten 1 stuck apex seal ussually, and stuck one will make a lil compresson ( would still make a small chhh noise...)

vaughnc

yeah, you need to determine if it's simply a flooded engine (non-critical low compression) or bad apex seal (rebuild time). Note it may take allot of cranking and near-starts before it will fire up. Once the oil film seal is re-established in the rotor chambers it should run MUCH better & idle smoothly... assuming the engine has good hot-compression (good apex seals).

hybridphil

The thing is..my 7 does fire up...and just today was able to idle for the first time in a while without me having to push on the throttle. Just idling, it will rev for a sec and then nearly stall, rev, nearly stall...etc. I just got a compression gauge today to check out another 7 that I was looking into buying just for the engine and when I showed up there realized I forgot the necessary 13/16 socket...After returning home, I decided to make use of the gauge and compression tested my car. When holding the pressure relief valve and cranking ( compression gauge in trailing hole of front rotor) it jumps evenly to about 70 psi and when valve is released, it evens out to just over 90 which I'm guessing means close to a rebuild anyways. When compression gauge hooked up to rear rotor, the gauge doesn't move at all, relief valve pressed or not. I know it's going to need a rebuild anyways but I just wanted to know the condition of my engine internally. Also, I was going to get started on the rebuild by draining my fluids. Would it be ok to drain coolant and let the car sit without it for a while considering that there is frost at night? I remember seeing an engine where the coolant seals leaked, coolant froze or something, and the housing cracked. I wouldn't want that....

SCCAIT7

Are you storing it inside or out? Even still... I would not drain fluids until you decided to pull the engine out. Make sure you have a good 50/50 mix in the coolant and she will not freeze....

RotaryResurrection

iTrader: (8)

You already know it's blown, I dont understand the question?

It is most common for rotaries to blow all 3 apex seals on one rotor at once, so you have no compression, no noise, no whooshes, no combustion, no nothing on the affected rotor. Which is what you have. IF you elect, you will require a rotor and a rotor housing be replaced (where the apex seals have damaged) in addition to regular seal kit.

www.rotaryresurrection.com ---> tech ---> internal engine damage

hybridphil

I guess I will just have to wait and see when I take it apart. I'll keep you guys posted. Thanks for the input!

drft_180sx

maybe you have one of those special edition 6.5B's ?? Sorry..i feel your pain. blown motors suck...and thats exactly what is sounds like to me from your description.