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Thread: LNF Compression Test

  1. #1
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    LNF Compression Test

    I suspect my car is having an issue with compression (possibly a bad ring). I plan on doing a compression test tomorrow. Already got the tool, but now my question is what is the proper procedure to do it with the LNF?

    I know I need to pull the fuse for the fuel pump and let it run until it dies, but what do I need to disconnect regarding the ignition/coils, should I do the test while the motor is cold, or let it get to operating temp first, and lastly should I pull all the plugs while testing the cylinders or only pull the plug of the cylinder I'm checking?

  2. #2
    Senior Tuner Iam Broke's Avatar
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    Do it warm, pull the injector fuses, all 4 plugs and coil packs.

    Crank it through 4-5 comp strokes for the cyl you are testing with the throttle open.

    Let it cool off before reinstalling the plugs to spare the threads. Easily damaged re-torqing them hot imo. You should see 150-165# across the board if in good shape. 90# is a dead cyl.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

  3. #3
    Quote Originally Posted by Iam Broke View Post
    Do it warm, pull the injector fuses, all 4 plugs and coil packs.

    Crank it through 4-5 comp strokes for the cyl you are testing with the throttle open.

    Let it cool off before reinstalling the plugs to spare the threads. Easily damaged re-torqing them hot imo. You should see 150-165# across the board if in good shape. 90# is a dead cyl.
    ^This.

    You can also do the "dry" test with a "wet" test to get a good average medium.

    Dry test is as explained.

    Wet test, you put about 1 cap full of oil into the cylinder and do the test again and then average the 2 numbers from the dry test and the wet test. It helps to solidify evidence of bad rings.
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  4. #4
    Senior Tuner Iam Broke's Avatar
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    If the ring lands are blown it won't come up with the wet test and oil consumption does increase.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    Just to be sure which fuse is the injector fuse or is it clearly marked?

    My car has been running fine. Raced a punk in a 5.0 the other day and we were dead locked so I'm not limping around. Just have noticed a fuel smell coming from my oil when I changed it yesterday so I figured I'd better be safer then sorry.
    Last edited by LNFnewb; 09-12-2012 at 09:08 AM.

  6. #6
    Senior Tuner Iam Broke's Avatar
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    I don't remember if they are marked on the LNF or not, no access to one right now.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    Quote Originally Posted by Iam Broke View Post
    I don't remember if they are marked on the LNF or not, no access to one right now.
    They did I found it, I had to run an errand for my mom so now I can't really do it today, because I have class at 4:30 and don't think thats enough time to let it cool off to put the plugs back in :\

  8. #8
    Senior Tuner Iam Broke's Avatar
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    I wouldn't pull the plugs out as soon as you shut it down either, let it cool off a bit first. That's why I said warm. No need to rip the threads out of the head.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    Quote Originally Posted by Iam Broke View Post
    I wouldn't pull the plugs out as soon as you shut it down either, let it cool off a bit first. That's why I said warm. No need to rip the threads out of the head.
    I let it cool down considerably, but made sure it was still warm. All 4 cylinders were right at 150psi, is that a good sign?

  10. #10
    Senior Tuner Iam Broke's Avatar
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    Yep, Like was posted in GMSC, you could do a leakdown test, but you need another tester.

    I think you are good. Mine ran 150-155 psi after 4-5 compression strokes.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    Quote Originally Posted by Iam Broke View Post
    Yep, Like was posted in GMSC, you could do a leakdown test, but you need another tester.

    I think you are good. Mine ran 150-155 psi after 4-5 compression strokes.
    I'm not going to worry about it for the time being. I'm satisfied with the compression test for now, because nothings been wrong with how my car has been running. I just smelled a bit of fuel when doing an oil change and got curious. lol

    I'm going to still do a leak down test, but it's not high on my to do list.

  12. #12
    Senior Tuner Iam Broke's Avatar
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    Send a used oil analysis into Blackstone Labs, they send out a mailable shipping sample kit free and for $35 it's a lot of piece of mind. Postage is $1.60 or so.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    Senior Tuner cobaltssoverbooster's Avatar
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    i blackstone every motor i make best insurance ever....
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    I just sent in a request for a free kit, there might be some slight contamination with the sample that I have. I stored the oil in a fresh container, but my oil pan may have had some left over oil in it from performing an oil change on my beater. However, I know if there are any indications of fuel in my oil that my LNF would be the culprit. lol

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    Not to bump an older thread but I did my compression test and got 125-130 across all 4. 1 and 4 were 125 but 2 and 3 were 130. I live in Colorado and was at 5500 ft above altitude but was wondering if that is normal. I sent a oil analysis to blackstone and they said they noticed some fuel in oil but not enough to cause concern.

  16. #16
    Senior Tuner Iam Broke's Avatar
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    Prob about right for your altitude. 155-165 is norm at sea level here. Since they are consistant, no worries. If you had a clinker at 90 I'd be concerned.

    My UOA always showed some fuel also.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

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    Your going to have some fuel smell in the oil due to direct injection. They are bad about fuel in the oil. I'd run pennzoil oil it fights against fuel better than Mobil 1. And I'd change it every 3,000 miles.

  18. #18
    Senior Tuner cobaltssoverbooster's Avatar
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    I run torco sr series with 5k changes
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  19. #19
    Could y'all post I link to the compression test tool and the leak down test tool, please?

    --Christian

  20. #20
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    My apologies for the thread revival, but I'm curious what the purpose is for evacuating the fuel before performing a compression test. Is this universal for all direct enjection engines?