well my car had flooded once again for some reason..so i figured i shud do a compression test done since the plugs were already out for the unflooding procedure.

back rotor ...84 psi
front rotor..87 psi

is this good or bad. this is before i started the car after the deflooding..when the plugs were still out.

 

You won't get accurate results testing a flooded engine. Unflood it, let it warm up and let the battery charge up, and THEN test it.

The same thing that causes the engine not to start, causes compression to be low. Which is why it won't start.

Remove EGI fuse, remove plugs, shoot excess fuel out, inject oil, clean and replace plugs, replace EGI, fire up. Let warm up or better yet drive it around a little, then shut it off, remove EGI and plugs, compression test.

90-100 is weak but still good enough to run.
100-110 is healthy.
110-120 is very strong.
120-125 is perfect.

 

from your posts it sounds like flooded engine shows lower compression. did i get it right?

 

hmm alright..thanks..ill give the test a try again. its just such a pain in the *** removing the plugs.

 

and i just unplug the ecu before the test...i dont think the injectors or the plugs fire with it unplugged...is it ok to do this ??

 

Just remove the EGI fuse from the engine compartment fuse box.

As far as conducting the test, you can get a general idea of the compression by using a conventional compression tester, but ya gotta know how to do it. Charge the battery first. Remove both leading (lower) spark plugs. Then you need to hold in the little button on the side of the gauge while you crank the car and read the maximum needle bumps for each rotor face. And you need to have someone depress the gas pedal to the floor while cranking the engine. The engine should be warmed up before the test, but that is not absolutely necessary.

Unfortunately, you cannot compare the readings with the Mazda specification unless you know the engine cranking speed at the time of the test. And you can't get that from a conventional compression tester. But, as I said, you can get a general idea of the health of the engine this way. Good luck!

 

is the EGI fuse one of the 2 big ones ....top one or the bottom?

 

The fuse box cover shows which fuse is the EGI fuse. The 3rd gen may have two of them as I recall. Check the shop manual.

 

hey guys how can I do a compression test to a 12a engine on the ground, meaning there is only the engine and no tranny. thanks.

 

http://www.rotaryresurrection.com/1s...ion_check.html

 

Thanks for the quick reply but this looks like to be tests on the cars with the engines mounted in and I am talking about an engine laying on the ground w/o a tranny

 

Read the first test:

 

Oh my bad :P, thank you very much!