compression test

[bryanmp3?]

i did a compresion test the other day 1,3,and 4 were all between 202 and 208 but num 2 hole was at 154 im going to pull the head soon but i dont know if i should just rering it or maybe i shuold run a bottle brush in it if itsnt so messed up. not shure what to do i dont have the money to rebuild the hole thing any ideas would be helpful thanks

 

[orng1]

Do you have a leak down tester? If you do you could tell if it's the rings, the gasket or a brned valve thats casing your problem. It doesn't sound too bad but it would be better if you could rebuild it. Don't go around boosting it, got to nurse it until you get some money might be able to last you a bit.

 

[Fudgie]

Throttle all the way open when testing #2?

 

[Captain KRM P5]

180psi on all cylinders is excellent for these motors, which is why i think you should run the test again, perhaps with a different tester. 120psi is the lowest allowable compression for these engines according to the FS engine manual, however a variance of 20% or more between two cylinders is usually a bad sign.

i assume the engine is running poorly otherwise you would not have done the test - whats the symptoms?

 

[bryanmp3?]

i dont have the power i used to have. it dosent get boost as fast

 

[TheMAN]

how many miles on the engine?

 

[bryanmp3?]

108 thousand

 

[jeffmsp]

is there any chance you have a leak at the exhaust manifold or a crack? I swore mine wasnt leaking once on my old motor but I pulled back the manifold a bit and saw how much exhaust one part of the gasket was leaking by the black buildup on the gaket in that spot around where it would seal around the port on the head. after retightening it build boost normally and drove better. torque specs is around 14-16 pounds for exhaust manifold bolts.

 

[bryanmp3?]

it dosent fix the compression

 

[orng1]

it dosent fix the compression

But if the mani is broken it will not allow to spool up as fast and may feel as it has less power.

 

[Captain KRM P5]

But if the mani is broken it will not allow to spool up as fast and may feel as it has less power.

thats true, but like he said it doesn't fix the fact that the compression test shows what it does.

 

[jeffmsp]

well then swap in a new motor. theres no magic way to fix your compression. 154 isnt that bad, im sure you could drive the motor for years still and it would not be too noticable. Another idea would be to pull your head, remove your upper and lower oil pan and then push the con rod and piston out through the head then replace with new rings and maybe a new piston. should not be that hard.

 

[bryanmp3?]

thats the plan thati had i was just wanting some input

 

[Alejo_NIN]

what are the right precedures for chekcing the compression?
i did mine with all sparkplugs off and got a 120 with 5 percent difference between cylinders

am i doing something wrong?

seems funny to be right at the border line

 

[Captain KRM P5]

what are the right precedures for chekcing the compression?
i did mine with all sparkplugs off and got a 120 with 5 percent difference between cylinders

am i doing something wrong?

seems funny to be right at the border line

the gas pedal needs to be at the floor while doing the compression test. if still remains that low but is also consistent across the board you engine may be timed improperly.

thats the plan thati had i was just wanting some input

i asked you some questions about your fuel management and ECU setup in another thread. you may have some very important concerns to address that brought you to this point.

 

[bryanmp3?]

and what are your concerns

 

[Captain KRM P5]

and what are your concerns

you are running an mp3 ecu, which for boost is typically not a good idea. it advances the timing too far even with high octane fuel to avoid detonation while in boost. if you are running a standalone engine management system, this is a non-issue but from the sounds of it you are not. i wanted to know how you are adding fuel into the system. if you method of adding fuel is incorrect, this in combination with the mp3 ecu could likely be the culprit for the damage done to your engine.

 

[onequickmsp]

Is there a complete compression test write up?? I would like to do one but I have no idea where to start. A friend has a compression test but he told me that every car is different and I have to find out how to do my car.

 

[1moreMPH]

^ im interested to. does a compression test just basically check the seal to the cylinders?

 

[Alejo_NIN]

i read in the mazdaspeed protege workshop manual that to accurately read the compression, you need to remove all plugs at once and check cylinder by cylder

connect ur compression tester where the sparkplug goes, remove the fuse for the injectors/fuelpump in the fusebox
try to start the engine three time and each time should last 3 seconds
the compression will start going up, and the highest reading will stay on the compression tester, that's ur copression
minimum is 100 and max...is whateve rit is.
i currently have 120 with about 3 or 4% difference among all cylders

if you ahve three with 120 and one with 150, there's somehting definately wrong.

if u want to know what's leaking, add some oil into the engine..if the compression continues to be bad...it is ur valves
if the compression actually increases, and it was low at first, it is ur rings...

no mater how good the engine is, if u add oil, it will alway raise the compression....but if by adding oil it goes over 200, i don't think it is the rigns
but i adding oil only gets it like around 150ish
then i believe is the rings...


someone prove me wrong, please