I keep hearing about it so I might as well get mine done. What kinda shops do this? Is it just your neighborhood garage kinda thing? I know the numbers are suppose to be close for every cylinder but what does it mean if they are waaay off.

I did search but couldn't find anything. :(

got a decent kit at Pep Boys for $30 bucks. Took me about ten minutes to do.

-just pull the fuel pump fuse
-start the car and let it die
-then remove 1 plug at a time, put the compresion tester on, preferably on that screws into the plug hole
- have a friend turn the key, let the engine crank over about 5 times and watch the guage.
- repeat for rest of the cylinders

If all is good the compression should raise at a fairly good rate on each stroke of the engine and after about 5 turns should be at maximum compression. The compression of the cylinders should all be relatively close to eachother. On my engine w/ a 121k miles it read as follows : 167,171,176,173. I did the check twice and each cylinder came up +/- 1 or 2 of those numbers.

If all 4 cyls are way off from eachother, something is wrong. If the compression doesn't build up quick or is low, something is wrong. Forgot what all the symptoms are, someone else will most likely pop in and let you know.

Make sure the engine is fully warmed up, you remove all the plugs, and hold the throttle wide open during cranking. You also need to have a good battery since cranking speed will affect compression readings.






Originally posted by dontblameme

-then remove 1 plug at a time,

the car won't start running, will it? do you just turn the car to the "ON" position or try to fully start the car?

I should probably do one on my 185k beast, too..

Originally posted by silversx
the car won't start running, will it? do you just turn the car to the "ON" position or try to fully start the car?

No the car won't start running, *** you pull the fuelpump fuse and you pull all the sparkplugs. It also doesn't hurt to pull the plug on the distributor so you don't shock yourself.

Lower than compression spec = rings going bad. If you get low compression, then try pouring some oil in the cylinder and if the compression is w/in spec, then your rings are worn.

The other test you may want to perform after your compression test is a leakdown test. This is where you pump air into the cylinder and record the percentage of pressure loss.

Michael.

Just a clarification that if you still have low compression after pouring some oil in the cyl, then it is either a cracked head, bad valves, or a big hole in your piston! (usually it is a bad valve or worn valve/seat.

Originally posted by Michael-Dallas
Lower than compression spec = rings going bad. If you get low compression, then try pouring some oil in the cylinder and if the compression is w/in spec, then your rings are worn.

remember people you have to let the engine crank 4 rotations. which is why they call it a 4 stroke. when u do 5 you get more compression then you should have!

Originally posted by HaulinSentra
remember people you have to let the engine crank 4 rotations. which is why they call it a 4 stroke. when u do 5 you get more compression then you should have!
That's not true. Just crank it until the gauge stops going up.

and make sure you listen to what probedude said:
"Make sure the engine is fully warmed up, you remove all the plugs, and hold the throttle wide open during cranking. "

Lots of people forget to hold the throttle open.

[QUOTE]Originally posted by jacen99SE
[B]
That's not true. Just crank it until the gauge stops going up.




Are you 100% positive on your statement? I have always heard 3 times is the correct amount. Now I'm really confused, because 3 turnovers compared to say 5 is a major difference on my motor.

111K miles... three cranks I get 150-155 on all four. Just checked it last weekend with a brand new accurate compression tester.

Can you please explain, because as I see it even if you did have some blow by there doesn't seem to me to be enough time for the cylinder to fully loose all the pressure you built up. Thereby showing a false, inflated reading the more you turn it over. I'm not saying you're wrong man, I'm just trying to have a clear understanding once and for all.

TIA

I checked 2 engines this weekend. Mine: 175/176/188/177, B15 I checked had high 180's to low 190's across the board.

Are you 100% positive on your statement?
Yes, I am.

Imagine your cylinder pressure is 175psi. Now matter how many times you crank the motor, your not going to get 200 psi into the gauge. The compression tester has a one-way valve that only lets air in. If you've got 175 psi in the gauge, and your engine compression is 175 psi, no more air will go into the gauge to increase the reading.

If you keep cranking the motor, your compression reading will increase rapidly at the start, then level off after a couple readings. Just crank it until the gauge stops going up.

Originally posted by HaulinSentra
remember people you have to let the engine crank 4 rotations. which is why they call it a 4 stroke. when u do 5 you get more compression then you should have!

They call it a 4-stroke because of their are 4 stages of internal combustion in this particular engine (and almost all cars for that matter). (1)intake - stroke down (2)compression - stroke up (3)combustion - stroke down (4)exhaust - stroke up. 4 exact rotations of the crank shaft will actually cycle those strokes 2 times.

No the car won't start running, *** you pull the fuelpump fuse and you pull all the sparkplugs. It also doesn't hurt to pull the plug on the distributor so you don't shock yourself.


The plug on the distributor? Is that the one to the ignition coil? Last time i tried to start my motor with that unplgged (by accident :tongue:) my friend said sparks were coming out...

The plug on the distributor? Is that the one to the ignition coil? Last time i tried to start my motor with that unplgged (by accident :tongue:) my friend said sparks were coming out...


unplug the larger of the 2 that are on the distrubutor, not sure which one that is off hand. oh yeah, and how many threads did you have to read through to get way back to this one? LOL :squint:

They call it a 4-stroke because of their are 4 stages of internal combustion in this particular engine (and almost all cars for that matter). (1)intake - stroke down (2)compression - stroke up (3)combustion - stroke down (4)exhaust - stroke up. 4 exact rotations of the crank shaft will actually cycle those strokes 2 times.


I was waiting for this to be brought to light :tongue:

That's not true. Just crank it until the gauge stops going up.

and make sure you listen to what probedude said:
"Make sure the engine is fully warmed up, you remove all the plugs, and hold the throttle wide open during cranking. "

Lots of people forget to hold the throttle open.

What if my car wont start so it cant warm up?

Wheres the fuel pump fuse?

is it just me or was this thread 2 years old and you brought it back...

No, this thread is actually 4 years old!