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I went and got a tester, and I am trying to perform a compression test. I disconnected the ESS, the 20A fuse for the fuel pump, and the Ignition Fuse which is the big black block. I have all the sparkplugs out, and when I try to crank it, it makes one click. The battery has power as the radio is blasting and working, and the windows. Is there something I'm missing or is there something I pulled out that caused it to not crank? The key light is also flashing rapidly, but it locks and unlocks just fine.. Most of the time atleast, only on occasion it wont work.
I went and got a tester, and I am trying to perform a compression test. I disconnected the ESS, the 20A fuse for the fuel pump, and the Ignition Fuse which is the big black block. I have all the sparkplugs out, and when I try to crank it, it makes one click. The battery has power as the radio is blasting and working, and the windows. Is there something I'm missing or is there something I pulled out that caused it to not crank? The key light is also flashing rapidly, but it locks and unlocks just fine.. Most of the time atleast, only on occasion it wont work.
Don't really need to do all that stuff. If using the RCTV 5.2 tester, you only need to remove the two top spark plugs (trailing). The fuel pump fuse isn't needed to be removed as you can cut all fuel to the engine by depressing the gas pedal. The ignition fuse you removed is probably the culprit. All I do is disconnect the spark plug boots and depress gas pedal while cranking. Eliminates any spark or fuel from the system.
Don't really need to do all that stuff. If using the RCTV 5.2 tester, you only need to remove the two top spark plugs (trailing). The fuel pump fuse isn't needed as you can cut all fuel to the engine by depressing the gas pedal. The ignition fuse you removed is probably the culprit. All I do is disconnect the spark plug boots and depress gas pedal while cranking. Eliminates any spark or fuel from the system.
I do happen to have the RCTV tester, I guess I was kinda freaking out about something blowing up haha, but thank you! I also do have the tester in the Leading hole which I think is the right one... but thank you very much!
The trailing plug is what is needed according to the directions. Printed right on my tester unless yours is different. Never tried in leading hole so unsure if that will cause a problem. You'll also want to leave your leading plugs in while testing as that will for sure skew your reading if testing with all 4 plugs removed.
Last edited by CaymanRotary; 12-22-2020 at 05:06 PM.
Disconnecting the ESS will cut fuel and spark, reinstall the ignition fuse and try again.
I just remove all the spark plug boots. That is enough to disable the ignition system. Pressing gas pedal down eliminates fuel. Easy peazy. Not sure if it works like than on S2 RX8's but for sure works on all S1's and RX7's I've tested.
Last edited by CaymanRotary; 12-22-2020 at 05:15 PM.
I just remove all the spark plug boots. That is enough to disable the ignition system. Pressing gas pedal down eliminates fuel. Easy peazy. Not sure if it works like than on S2 RX8's but for sure works on all S1's and RX7's I've tested.
Got numbers... very worrying as they're in PSI, Rotor 2 was 49, 50, 59 PSI @280RPM and Rotor 1 was 50, 59, 50 PSI at @260RPM. It never did normalize and the block is cold because it took me too long to get it tested.. I would assume they're inaccurate hopefully, the car ran just fine today as well, no lumpy idling, no hesitant accelerating which still suprises me but its very possible..
Last edited by RX-8 40th Anniversary; 12-22-2020 at 06:09 PM.
The clicking but not turning is your battery being too low. to turn the engine. Radio, locks, take very little current compared to the starter motor. This also means that it's not really turning the starter at 280rpm.
Got numbers... very worrying as they're in PSI, Rotor 2 was 49, 50, 59 PSI @280RPM and Rotor 1 was 50, 59, 50 PSI at @260RPM. It never did normalize and the block is cold because it took me too long to get it tested.. I would assume they're inaccurate hopefully, the car ran just fine today as well, no lumpy idling, no hesitant accelerating which still suprises me but its very possible..
That cant be right thats like 3-4 bar, the engine wouldn't even run with those numbers. You aren't testing with all 4 spark plugs out right?
That cant be right thats like 3-4 bar, the engine wouldn't even run with those numbers. You aren't testing with all 4 spark plugs out right?
Nope, Just the trailing plug out. Leading plugs are still in and the tester was in the trailing hole too. I'll try again tomorrow hot and see what results I get again since this was my first time actually testing it by myself. I don't think its common but is it possible the tester is... faulty?
I only disabled the ESS, and took out the fuel pump relay as well as unhook all the plugs. I did take out the leading plugs on accident and got no PSI and was wondering what I did wrong.. Then I put it back in and got the results but I couldn't think they were accurate. This was also on multiple tries as well, and the car starts up cold with hot-start problems..
No hesitant idle issues and no stalling issues.. So I'll try again and double-check everything and see if there's any difference.
The clicking but not turning is your battery being too low. to turn the engine. Radio, locks, take very little current compared to the starter motor. This also means that it's not really turning the starter at 280rpm.
I did have some battery issues a while back but they went away... I got it tested and different companies told me it was fine... I'll double check the battery connections if anything. Turned out it was the ignition fuse not being plugged in hah..
I mean, sounds like you did it right. But since you are having hot start issues as well, this isn't sounding very good at all. May actually have to replace that engine.
I mean, sounds like you did it right. But since you are having hot start issues as well, this isn't sounding very good at all. May actually have to replace that engine.
I was prepared for it, I am planning to get it rebuilt by rotary resurrection, maybe a bridgeport. It drives just fine, and my father recommends that I just drive it until it just doesn't turn over, which is what I would love to do if I wasn't fearful of the seals falling out and ruining the entire combustion chamber heh..
I will do another test as it was done when cold and double check to see if I even plugged the tester in correctly.. I am still fairly new to rotaries but I try to learn as much as possible, and ever since the guy who sold me the car drove it like how it should be, I seriously fell in love with it... damn rotaries
I will keep you all updated and if I get the same results, well I will document the next engine build
Definitely go with a new engine if yours is too expensive to fix. If you do rebuild a bridge port isn't necessary. It won't really give much benefit to a stock RX8. Port polishing is all that is required. Good luck! Maybe try to give the test on the warm engine again and see what happens. Those numbers shouldn't be that low.
Seals don't really fall out. I suppose one can crack and fall out but your compression is apparently low everywhere, which points to wear rather than damage. That said, your housings are probably not in great shape already, so I would also recommend a rebuilt engine rather than rebuilding yours.
I had one comp test (with the same tester I think) that showed 80 psi in 2014. Since then every other test has been over 100 to this day. Not sure why, but these things happen, apparently.
That cant be right thats like 3-4 bar, the engine wouldn't even run with those numbers. You aren't testing with all 4 spark plugs out right?
I had a engine in my Rx8 with similar compression when hot and it ran completely normal. I could tell it was down on power just from having owned Rx8's since 2010 but there were no other recognizable symptoms of low compression believe it or not. While I don't believe the OP is doing everything 100% correct with his compression test at the moment (though it is possible OP is), its definitely not impossible for his motor to run at those compression numbers. That said however, his compression numbers are definitely indicative of his motor being toast assuming he is testing correctly regardless of if those are the hot or cold numbers.
I had a engine in my Rx8 with similar compression when hot and it ran completely normal. I could tell it was down on power just from having owned Rx8's since 2010 but there were no other recognizable symptoms of low compression believe it or not. While I don't believe the OP is doing everything 100% correct with his compression test at the moment (though it is possible OP is), its definitely not impossible for his motor to run at those compression numbers. That said however, his compression numbers are definitely indicative of his motor being toast assuming he is testing correctly regardless of if those are the hot or cold numbers.
I want to think there is something wrong I am doing, but wouldn't be suprised if it is that low, because the motor barely started cold, but I didn't charge the battery after cranking atleast 3-4 times to double check the numbers, PO335 code threw out though but I would assume its because of the ESS. Taking it out again and will re-do the test once I get back.
I would run the engine to normal operating temperature and run the test again. Compression tests should be done with the engine at normal operating temperature.
When I do a compression test, I just the 20A fuel pump fuse and hold the throttle open. Thats just me. No need to remove the ignition fuse as mentioned above. The ESS connector being removed from the eccentric shaft position sensor does in fact cut spark and injector pulse. The fuel pump will still operate and pressurize the fuel system. Do what makes you comfortable. Bit definitely repeat the test with the engine warm and the throttle depressed 100% when cranking.
not sure if my memory is correct, but I believe pulling the room fuse; which cuts the PCM from being powered (no fuel or spark) and then either jumping the starter solenoid power connections or the starter solenoid will get it to crank. The MOP won’t be operating either, but for cranking only to make a compression test it shouldn’t matter much, but should not be over abused either. You have to be absolutely sure it’s not in gear either or the car can potentially lurch forward to ruin your day/life.
I want to say that when the throttle is held down that in addition to cutting fuel it also results in the MOP going max setting too (my memory is not clear on this, been a while)? This would be good for helping overcome a fuel-flood situation, but could lead to an erroneous compression reading being higher than actual. The extra oil provides additional sealing that would otherwise not exist under normal operating conditions.
IMO it’d also be better to disconnect the ignition coil harness/control-wiring connectors rather than just pulling the spark wires off the plugs for those who choose that method. There’s no need to be powering and charging up the coils if the intent is not to discharge that potential energy as well. There’s a safety factor with that too.
12-22-2020, 04:50 PM
RX8 refuses to crank for compression test
Then I put it back in and got the results but I couldn't think they were accurate. This was also on multiple tries as well, and the car starts up cold with hot-start problems..
