The Autonerdz Community Forums - In cylinder compression testing

TomSr71

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In cylinder compression testing
Dec 16^th, 2014 at 6:30pm

I have a 2001 Nissan 3.0 as a trainer car it starts and stalls fairly fast I am trying to learn as much as I can from the in cylinder test. I am not in a hurry to fix this car but would like some input on analyzing the results I have. With a mechanical compression gauge I am getting around 225psi after 10 seconds cranking. This is similar on all 6 cylinders. This is a learning car so I am not rushing o fix just get some experience with scope.

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_2_2001nissan_timming_problem_maybey.psdata (142 KB | )

2001nissan_timming_problem_maybey.psdata (148 KB | )

2001_Nissan_Maxima.psdata (4088 KB | )

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TomSr71 Freshman Member Picogroup Offline Posts: 18 Logan Iowa USA Gender:	Re: In cylinder compression testing Reply #1 - Dec 16^th, 2014 at 6:42pm The last file I uploaded is running test and on frames 15 - 16 is the engine stalling. This is the first car I have done in cylinder compression test with scope. I noticed is as engine stalls the pressure increases is that normal?
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dennisb Senior Member Offline I'm an Autonerd Posts: 145 benton Tennessee USA Gender:	Re: In cylinder compression testing Reply #2 - Dec 16^th, 2014 at 6:59pm tom i would like to see cam and crank signals along with comp. capture to help verify timing. the capture you posted does not give enough info to tell what has taken place if timing is off. dennis
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TomSr71 Freshman Member Picogroup Offline Posts: 18 Logan Iowa USA Gender:	Re: In cylinder compression testing Reply #3 - Dec 16^th, 2014 at 7:17pm I should have some time tomorrow for cam and crank.
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Abndanger LSD Guide Picogroup Offline Posts: 2,141 Grand Rapids, Mi Michigan USA Gender:	Re: In cylinder compression testing Reply #4 - Dec 17^th, 2014 at 12:30am Tom, along with cmp & crk would like to see a sync on the coil for that cylinder. Don't forget to connect a spark tester to the coil. Don't want to damage a driver. Maybe HarleyMike will step in here. He works at a Nissan dealership
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HarleyMike Super Nerd Picogroup Offline Posts: 1,308 Dinwiddie County Virginia USA Gender:	Re: In cylinder compression testing Reply #5 - Dec 17^th, 2014 at 5:29am http://www.autonerdz.com/cgi/yabb2/YaBB.pl?num=1418010021 Reply #3 from this link are the cam specs.
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HarleyMike Super Nerd Picogroup Offline Posts: 1,308 Dinwiddie County Virginia USA Gender:	Re: In cylinder compression testing Reply #6 - Dec 17^th, 2014 at 7:51am Hey Tom, the next time you are poking around under the hood could you let me know if that engine has an EGR valve. Some did and some didn,t in 01. If it has one it will be buried under the IAC valve and hard to spot, I think it would be electric also. And also what cylinder are you testing?
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Tom Roberts

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Re: In cylinder compression testing
Reply #7 - Dec 17^th, 2014 at 9:01am

TomSr71 wrote on Dec 16^th, 2014 at 6:42pm:

I noticed is as engine stalls the pressure increases is that normal?

Yes. Compression pressures and intake pressures have a direct relationship. Intake pressure higher then compression pressure is higher. That's why cranking compression pressure is higher than running pressure.

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intcomppress.gif (109 KB | )

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TomSr71 Freshman Member Picogroup Offline Posts: 18 Logan Iowa USA Gender:	Re: In cylinder compression testing Reply #8 - Dec 17^th, 2014 at 6:42pm I had a quick chance to get cam and crank today
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JNelson Super Nerd Picogroup Offline I'm an Autonerd Posts: 684 Livermore, CA California USA Gender:	Re: In cylinder compression testing Reply #9 - Dec 19^th, 2014 at 9:00pm Tom, wow. That is a great pic, shows how direct the pressures are connected.
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Logic

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Re: In cylinder compression testing
Reply #10 - Dec 20^th, 2014 at 12:09am

JNelson wrote on Dec 19^th, 2014 at 9:00pm:

Tom, wow. That is a great pic, shows how direct the pressures are connected.

Absolutely bravo..........

I take it that all the engines in this discussion are similar.

Petrol?

Tom, Do you have a know relationship between these parameters and a common rail diesel, can one make the same comparison?

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JNelson Super Nerd Picogroup Offline I'm an Autonerd Posts: 684 Livermore, CA California USA Gender:	Re: In cylinder compression testing Reply #11 - Dec 20^th, 2014 at 8:11am Logic, thinking about intake pressure/vacuum I try to start from absolute zero pressure. Then the pressure under boost from diesel is no different (just slightly higher in the scale) that intake vacuum. So I would think the relationship would be the same.
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Tom Roberts

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Re: In cylinder compression testing
Reply #12 - Dec 20^th, 2014 at 8:46am

Logic wrote on Dec 20^th, 2014 at 12:09am:

Absolutely bravo..........

That's a capture Brian did some time ago just goofing around.

Logic wrote on Dec 20^th, 2014 at 12:09am:

can one make the same comparison?

I freely admit I am diesel illiterate. But if intake pressures change then I would think that we would have the same effect. However, doing an in cylinder pressure test for that long would likely kill the transducer from the heat of compression.

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