my compression results.. doesnt look good

[DJ_Sunrise]

i ran a check on my car, i am running about 150-160 in all four cylinders, with a hot engine on a blistering NJ day. wonder what could be the problem???

~Sunrise

[fastpace]

that really isn't that bad, that is decent. Are you sure you followed all of the steps to checking your compression?

[mendozasport]

let me but in , how did you mesure compresion? what was the water temp? and what engine do you have ?

[DJ_Sunrise]

aww crap, thats right.. i forgot to mention that. S13 KADE, with 139,xxx miles on her. i like how its nice and consistant, :hsdance: but i was 95% sure that the PSI should be a lot higher then that? well.. when i did it, i had my center plug from distributor grounded to the engine, and i went one spark plug at a time. after i inserted the gauge nice and tight, id crank the engine for a couple of seconds. water temp was 3 notches up from 0. im supposed to step on the gas pedal right? how much different will the compression be if its not stepped on? in my haste, i think i mighta forgotten to keep the gas pegged.. :bash:

~Sunrise

[orion::S14]

...i went one spark plug at a time.

You mean you only removed one at a time???

All the plugs need to pulled to get a proper reading.

And holding the throttle wide open is correct, make sure you either pull the fuel pump fuse or unplug each injector.

- Brian

[kandyflip445]

Just pull the pump fuse and run the car till it dies to get all the fuel out of the line. When putting it back together turn the key to accessory ~3 times to build up pressure in the line before you start again.

[Jeff240sx]

Spec is 179 +/- 15% iirc. So recheck your methods and if it's 160, that's within spec. Also, some gauges read funny. The gauge at Secret Services reads a KA at 210-220psi. It's better to either know a) your gauge is dead on, or b) you're consistant.
-Jeff

[orion::S14]

Jeff -

You're correct about the 179 as stadard spec.

But the difference per cylinder limit is 14psi as a max...

And the "rebuild" spec is 155 for a KA.

And some guages do read high or low...at 155-160psi, before I'd consider a rebuild, I'd try another gauge.

That's if those numbers were gained using the proper method...

Again, did you remove ALL the plugs before testing any one cylinder???

- Brian

[DuffMan]

14psi isnt the max difference from 179 its the max difference between cylinders, so as long as they're all consistant and above 150ish you are fine.

[orion::S14]

Duffman -

You and I are saying the same thing. As long as there's no more than 14psi difference across the 4 cylinders, you're OK...if the readings are around ~170-180. i.e. 171/185/178/174 is fine, normal spec KA, healthy.

...so as long as they're all consistant and above 150ish you are fine.

Or all your rings are similarly worn out, and you still need a rebuild.

If I had 154/150/162/150, I'd be worried.

Again, before I went as far as a rebuild, I'd repeat the test with a (known good) compression gauge to see if my numbers were still low.

- Brian

[DuffMan]

Duffman -

You and I are saying the same thing. As long as there's no more than 14psi difference across the 4 cylinders, you're OK...if the readings are around ~170-180. i.e. 171/185/178/174 is fine, normal spec KA, healthy.

Ok, it was a bit confusing the way you wrote it.



Or all your rings are similarly worn out, and you still need a rebuild.

If I had 154/150/162/150, I'd be worried.

Again, before I went as far as a rebuild, I'd repeat the test with a (known good) compression gauge to see if my numbers were still low.

- Brian
I wouldnt be worried by compression numbers like that. Its normal for older cars to have a bit of blowby through the rings. It might consume a bit of oil like that, but still be healthy.

I woudn't turbo it though :cool:

[Colorado S14]

I live at 5500ft. do you think that altitude will skew the readings down. I have a 1997 KA that gets 155-160 psi. across the board. I would like to go turbo. I added a cap of oil and they only raised pressure by about 5 psi.

[orion::S14]

Duffman -

Agreed.

- - - - - - - - - - - -

thul -

Yes, I think the altitude will skew those numbers...

It's good that oil only raised it 5psi...that means the rings are good.

So either it's the altitude, or the gauge just reads low.

- Brian

[Chernobyl]

5500 ft = 82% atmospheric pressure

179psi * 0.82 = 147psi

so 155-160 sounds to be pretty much dead on.

[DJ_Sunrise]

sweet, ty for all the help guys, ill recheck the compression and post my results again. hope it turns out well.


~Sunrise