NoPistons -Mazda Rx7 & Rx8 Rotary Forum

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-   -   Self Compression Test... (https://www.nopistons.com/2nd-generation-specific-17/self-compression-test-24903/)

FrestyleFC3S 09-17-2003 09:05 AM

i talked to a few of you yesterday about this problem im having.....im not gonna get into the problem yet maybe later if this doesnt work



but im gonna change the spark plugs cause theres a chance they can be rfeally fouled up .....while theyre out im gonna do a self compression test....basically the audio test where you listen for the rotors moving



how exactly do you do that....



take out plug, pull egi fuse...then what...crank the engine?....how many should i do at a time? etc?



thanks guys



- mike

Baldy 09-17-2003 09:15 AM

I would take out spark plugs for 1 rotor, remove fuse, then crank. Replace spark plugs, then remove plugs from the other rotor, and crank.



I've only listened to compression with no exhaust on, not through the spark plug holes, so I'm not sure exactly what it would sound like. But you should hear 3 sounds, swooshes or something. If compression was bad, you would not hear 3 consistant sounds.

Jims5543 09-17-2003 09:58 AM

I think you can borrow a piston engine compression tester from Autozone. Just remove the trailing plug from the front and rear rotor housing. Pull the EFI fuse on your fuse block under the hood. Then take the compression tester and remover the schrader valve from it. Thats the little nipple thingy in the middle like I bike tire has. Screw it in and have someone turn over the engine while you watch the tester. You should see the needle bump 3 times all the same.



Good luck.





Make sure you pull all you plg wires.

MazdaEnthused 09-17-2003 01:04 PM

i need to get a compression tester my self how much do they run??

UniqueTII 09-17-2003 01:16 PM

$45 at Napa.

FrestyleFC3S 09-17-2003 01:59 PM

well theres no vac leak i can see .... i changed the spark plugs so im at a loss...im gonna get a compression test to check out the engine next...its only got like 30-40k miles on it so this sucks



ima go cry

Jims5543 09-17-2003 02:19 PM

FrestyleFC3S - What is the car doing or should I say not doing. I missed the memo.

Nemesis 09-17-2003 02:29 PM

Self Compression Test:



1) Stick finger in ass

2) Hold breath

3) Squeeze body as tight as possible

4) Repeat three times



If you explode or **** yourself, you failed.

FrestyleFC3S 09-17-2003 02:32 PM

jim....it wont idle for ****....the engine and body of the car rock heavily like massively and it wont hold idle well...it clicks around at 5-700 depending on what it wants to do...the boost gauge shows the vac pressure going crazy too..just bobbing and not stable at all



its loud and sounds like a v8....sometimes it stalls



i changed the plugs, checked the lines, and need to check compression...coming to the conclusion that its a dead engine :(

UniqueTII 09-17-2003 02:47 PM

Can you hear any noises inside the engine while it's running? I've heard two blown rotaries and they sounded exactly alike...there was a definite metallic sound coming from the engine.

MazdaEnthused 09-17-2003 03:44 PM

sweet i'll have to pick one up... and all i do it thread it into the spark plug hole and crank it over?

FrestyleFC3S 09-17-2003 10:53 PM

yea im pretty sure its blown...i had two guys around here listen and theyre pretty sure too...theyre rotorheads over at the evil forum but cool nonetheless ima try and get them in here



anyways looks like its time for :



rebuild kit....haltech....ito ports...720s .... any other suggestions....



im thinkin around 2500 for the full rebuild and everything....im gonna be doing it all myself with djgiantrobot and the guys up here in newark, DE....

FrestyleFC3S 09-17-2003 10:56 PM

oh i forgot....upgraded fuel pump, gotta figure out which will be best for me....and then .... dun dun dun.... fmic

94touring 09-17-2003 11:14 PM

What about the map sensor? Did the little hose come off? If you pull the plugs you should hear loud thumps as the motor turns over.

FrestyleFC3S 09-18-2003 12:24 AM

yea people said to check that...but im almost 100% positive that its dead

adamlewis 09-18-2003 12:41 AM

I always thought you were supposed to plug the tester into the leading hole since its larger...?



Also, you need to hold the throttle all the way open while youre cranking it over and doing a compression test.

TheCamel 09-18-2003 04:54 AM

Ok here are the steps to the compression test.



1) make sure you have a good battery

2) pull the EFI fuse

3) pull both leading or both trailing plugs or all of them ( but do not mix and match the plug holes you are getting the readings from, they must be out of the same holes, both leading or both trailing

4) install compression tester in first hole, there are two ways you can do this to get the correct reading. Most gauges have a peak hold button on the side, you can either hold this button, or remove the schrader valve in the bottom of the gauge hose

5) prop the throttle open or have it held to the floor so that there is no restriction for the air that you will be measuring.

6) crank the engine over and observe the gauge this is easier with a second person or a starter button, if you do not know what a starter button is or does find the second person to help

7) watch for the needle to jump as the engine is cranked over, make sure you get at least 6 revolutions of the motor

8) record the readings and move the compression testor to the next rotor and repeat step 6 and 7

you should have 3 distinct needle jumps reading in the 100's or higher

9) post your compression readings for everyone to see, you will know if there is a blown apex seal(s) from the reading





Hope this helps

djgiantrobot 09-18-2003 10:54 AM

make sure the engine is HOT when you do this

Jims5543 09-18-2003 11:08 AM

Your engine is blown. It sounds like it is doing the death shake to me. It looks like a paint mixer from home depot at idle right? No power. It sort of smooths out at higher RPM but there is still no power.



You can do a compression check to confirm this. From what you decribed to me it sounds like it is blown.

FrestyleFC3S 09-18-2003 11:25 AM

yeap....jims i think we all have this correct assumption



dj ur coming over this weekend though right?...we can do this with the one you have....and im gonna start to order the parts this weekend - next week



these guys here in newark down the road from me are gonna let me use their house and stuff to pul lthen engine and rebuild at....so we got a place to do it now....


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