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Old 02-05-2009, 04:16 PM
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Join Date: Jun 2007
Posts: 46
spark plug tips stuck

Hello out there,

Changing my plugs and the tips on the old plugs are stuck in the rubber boot in the wire. I've tried removing the tips from the boot but they are stuck even when I try and screw the plug back in to the tip to pull it out...any thoughts? The plugs I bought, the tips are permanent. 1990 420 SEL


Last edited by bigdukesix; 02-05-2009 at 04:30 PM.
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Old 02-07-2009, 12:27 AM
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Join Date: Nov 2002
Posts: 681
i forget WHAT the correct plugs are. i would try, in your case, lotsa wd-40 and lotsa time. spray the boots, screw the old plugs in and wiggle alot for a long time. i have NEVER had tips stick so bad that i had to unscrew the plugs from the wires. but, make sure you have the right plugs to install. good luck, chuck.
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Old 02-07-2009, 01:52 AM
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I would NOT use WD-40, under any circumstances. The boots are high voltage insulators, and any petroleum product not designed for the purpose will ruin them. You could try soaking in rubbing alcohol, but let dry completely before use.

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Old 02-07-2009, 07:07 AM
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Location: Lafayette Indiana
Posts: 33,234
I think maybe you misunderstand the plug wire setup.

ON most gasser mercedes you remove the screw on tips and the threaded center is what the plug wire attaches to.
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Old 02-08-2009, 06:50 PM
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Can't help with removal from the boot but after you get them out, wipe the inside of each boot with dielectric grease. Use a Q-tip for application. This is high temp. resistant and will prevent the same thing from happening the next time.
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Old 02-11-2009, 07:28 AM
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Join Date: Jun 2007
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Spark plug tips stuck

Thanks for all the replies. T Walgumuth was right, removing the screw on tips of the spark plug is the correct procedure.
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Old 02-11-2009, 09:40 PM
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No, you really DO NOT want to use WD-40 in a plug wire. Anything except dielectric grease has the potential to create a carbon track which will cause all sorts of misfire and ignition issues.

If they're stuck real bad, even if you do get them out, the electrode may not be very healthy anymore. Might be time to replace them.

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