quick and easy compression testing

ovendenk · Post by **ovendenk** » November 16th, 2005, 11:28 pm

alright today i was determined to get my compression results from my new motor. i eventually tracked down a compression tester for $13 at princess auto (princessauto.com) and i also got a squeeze type starter switch for $3. the advantage to using the switch is that you don't need to disconnect anything electrical. DON'T EVEN PUT YOUR KEY IN THE IGNITION.

all you do is disconnect the wire from the solenoid that's clipped on and connect the two switch clips to where the red circles are in the pic. then one by one you unscrew the spark plug and screw in the compression tester only hand tight and hold the starter switch until you've reached maximum pressure on the tester. it should only take about 5 seconds per cylinder. write down the results and release the pressure, then unscrew the tester and put the spark plug back in and move on to the next cylinder.

15 min and i was done my very first compression test. i got 205, 215, 205, 210, 215, and 210 for my #1 through #6 respectively.

Grants · Post by **Grants** » November 16th, 2005, 11:33 pm

Good description and pic! Great idea the squeeze switch.

AND good results on the test!

jschrauwen · Post by **jschrauwen** » November 17th, 2005, 5:30 am

Nice job Kevin!!
FWIW, I believe it's best for that process to have all of the spark plugs out ahead of time. And then go from cylinder to cylinder to do the test. The remote starter looks to be a pretty handy tool.

ovendenk · Post by **ovendenk** » November 17th, 2005, 8:30 am

thanks guys. btw, you can use and any switch you can find. and the reason i like using the switch is because you can use it under the hood and watch the pressure gauge as you turn over the engine and make sure everything is ok.

jschrauwen · Post by **jschrauwen** » November 17th, 2005, 1:20 pm

Kevin, those are some pretty high compression numbers. These are from the (yet to be installed) ZE? I thought max compression available for the ZE was 210lbs??? If that's the case than perhaps leaving the other remaining spark plugs in while doing each cylinder may taint the teast readings. Anyone else confirm this?

ovendenk · Post by **ovendenk** » November 17th, 2005, 1:38 pm

does it matter that i loosened them all? i wanted to do it quickly, so i unscrewed each of them about 2 rotations to be able to take them out by hand. then, i hand tightened them.

i'll redo the test and let you know what the numbers are without plugs.

btw, i did each cylinder twice for accuracy. and this was on a cold engine since i have no tb, alt, rad, or disty to run the engine with.

jschrauwen · Post by **jschrauwen** » November 18th, 2005, 8:51 pm

Something else I just remembered, was that the TB is supposed to be held open when cranking the engine over for each test.

ovendenk · Post by **ovendenk** » November 19th, 2005, 12:46 pm

ran out of time to do the retest with no plugs, but i don't think the intake could get anymore open since i have no tb or intake system on the ze car right now.

tomorrow night, i'll redo the test.

ovendenk · Post by **ovendenk** » November 20th, 2005, 10:13 pm

alright, pulled the plugs and redid the test. i got 202, 220, 205, 210, 216, 212 with no plugs and 205, 215, 205, 210, 215, and 210 with slightly loosened plugs for the #1 through #6 plugs respectively. basically the same.

should i be concerned with the 20psi difference between #2 and #1?

jschrauwen · Post by **jschrauwen** » December 16th, 2005, 1:46 pm

"Oven", those are still pretty high numbers for a ZE and I was hoping by now someone could step up and confirm what the "majic" number or max compression reading should be. You're still within the 10% range Kevin.

ryanlindenberg · Post by **ryanlindenberg** » January 10th, 2006, 4:12 pm

it's probably because he has no intake manifold... is it even possible to have compression that is too good?

ovendenk · Post by **ovendenk** » January 10th, 2006, 4:54 pm

ryanlindenberg wrote:it's probably because he has no intake manifold... is it even possible to have compression that is too good?

when did i say i had no IM? when the test was performed both times the intake manifold was securely attached. the only thing i did wrong on the first test was not removing the spark plugs. i just removed the plug in one cylinder, did the test, then put it back and moved on to the next cylinder. the second test was performed with no spark plugs.

ryanlindenberg · Post by **ryanlindenberg** » February 8th, 2006, 6:52 pm

ovendenk wrote:
ryanlindenberg wrote:it's probably because he has no intake manifold... is it even possible to have compression that is too good?
when did i say i had no IM? when the test was performed both times the intake manifold was securely attached. the only thing i did wrong on the first test was not removing the spark plugs. i just removed the plug in one cylinder, did the test, then put it back and moved on to the next cylinder. the second test was performed with no spark plugs.

well when you said:

but i don't think the intake could get anymore open since i have no tb or intake system

considering that the intake manifold is part of the intake system...

fieromx3 · Post by **fieromx3** » February 8th, 2006, 7:13 pm

i beleive the compression for a ze is 220 psi irc

ovendenk · Post by **ovendenk** » February 8th, 2006, 11:20 pm

ryanlindenberg wrote:
ovendenk wrote:
ryanlindenberg wrote:it's probably because he has no intake manifold... is it even possible to have compression that is too good?
when did i say i had no IM? when the test was performed both times the intake manifold was securely attached. the only thing i did wrong on the first test was not removing the spark plugs. i just removed the plug in one cylinder, did the test, then put it back and moved on to the next cylinder. the second test was performed with no spark plugs.
well when you said:
but i don't think the intake could get anymore open since i have no tb or intake system
considering that the intake manifold is part of the intake system...

true enough although it was a mix up. i have the intake manifold, but no tb or intake tubing. sorry for the confusion.