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Thread: Car will not start after replacing spark plugs: Solved

  1. #1
    Join Date
    Apr 2018
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    Chicago, IL, USA
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    3
    My Cars
    2010, 530i

    Car will not start after replacing spark plugs: Solved

    After replacing spark plugs and tightening to the specified torque, started the car and it started as expected. When I tried starting again after it was sitting idle for two weeks or so, it will not start. Went through many forums without any help. Some mentioned about defective plugs although new. Never experienced defective new plugs before but decided to put the old plugs back to see if it will start. To my surprise, the new plugs came out without any effort, although they were tightened to 2 3 ± 3 N m ( 1 8 ± 2 f t - l b ). Replaced #1 plug and hand tightened using 6 inch ratchet and re-tightened the remaining 5 the same way. Stared the car and it stared without hesitation. Replaced the #1 plug with new plug and problem solved.

    Because I had visited many forums for help, I wanted to share my findings with the DIYers.

  2. #2
    Join Date
    Sep 2008
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    Brentwood, CA
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    276
    My Cars
    2000 528iT; 2008 550i/6
    I'm sorry but I'm unclear as to your solution: did you remove ALL 6 of the new plugs and reinstall the 6 old plugs, or did you have to simply replace ONE of the new plugs?
    2007 530i sport (Montreal Blue w/ gray interior)
    2008 550i sport (Alpine White w/ black interior)

  3. #3
    Join Date
    Jan 2009
    Location
    Antelope, CA
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    424
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    1997 BMW 528i
    Quote Originally Posted by ZeroDfx View Post
    I'm sorry but I'm unclear as to your solution: did you remove ALL 6 of the new plugs and reinstall the 6 old plugs, or did you have to simply replace ONE of the new plugs?
    The new plugs weren’t torqued down all of the way, so he lost compression on all 6 cylinders.

    Good rule of thumb, get them snug, and then crank them down a 1/2 to 1/4 turn.


    Sent from my iPhone using Tapatalk

  4. #4
    Join Date
    Apr 2018
    Location
    Chicago, IL, USA
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    2010, 530i
    Sorry for such a late response.
    What I found out was that the spark plugs were not tight enough to create required compression. To troubleshoot the issue, I just replaced the spark plug in #1 cylinder with the old plug but in the process of doing so I realized how essay it was to unscrew the new spark plugs which were installed about two weeks back.
    In a nut shell, the problem was with plugs not torqued enough to create required compression in the cylinders. It is very likely that I did not set the torque meter to the correct value.

  5. #5
    Join Date
    Feb 2014
    Location
    Long Island NY
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    28
    My Cars
    2005 3.0 530i
    Interesting thread. The only thing that comes to mind other than incorrect torque setting is if the old plugs were hard to take out maybe the threads were a little resistant to accepting the new spark plugs and they felt like they seated all the way. When applying the torque wrench the resistance enabled the torque setting to be reached. Just a guess. I agree with the seat plugs and then 1/4 to 1/2 turn thereafter. I have been turning wrenches for so long there are plenty of bolts and nuts I do not torque, but go by feel.

  6. #6
    Join Date
    Sep 2017
    Location
    Chestermere, Alberta, Can
    Posts
    70
    My Cars
    2008 BMW 535xi
    Yeah, but a partially threaded spark plug would not relieve compression appreciably. Something else must have been wrong, like perhaps improperly connected coils.

  7. #7
    Join Date
    Sep 2006
    Location
    Michigan
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    13,674
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    2005 325Xi
    Right. Unless the plugs all shot out of the cylinders, there'd be enough compression to get the engine running.
    Quote Originally Posted by B4SH View Post
    If anyone knows, it's this guy who knows literally nothing about everything.
    Quote Originally Posted by fcvapor05 View Post
    Do you even OT? The mean 401k around here is probably about $6, what with all the shiny cars and $1,000 watches and donations to get other members' Volvos running.


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