changing spark plugs E420

OK. This is a silly note, I admit. I'm trying to change spark plugs on my '94 E420. Problem is, I can't get the connector off the end of the plug. I've changed lots of plugs on other cars, but not on a Mercedes.
Is there a special tool you have to use to get the plug connector off, or are mine just stuck on real tight. I don't want to just keep pulling and damage something. Advice anyone?
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Yes, there IS a tool to pull the lead off the spark plugs. Some owners claim not to need / use it but a set of wires is expensive. Dealer and others sell tool.
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Thank you for the answer.
And expensive isn't the word for it. A set of plug wires costs anywhere from $250 to $450, depending on which store gives me the quote. Any idea why?
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If this one is like a E320 tool I made one myself from a old open end wrench by bending it to offset it a bit worked fine I can send a photo if you email me Bob

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There are tools out there. I got one from Sears. It has red handles and red rubber around the jaws. www.fountainpenhospital.com sells it as a fountain pen tool, but sears has it for cheaper. Richard

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Take a pair of long nose, or needle nose pliers, and grab the metal barrel end of the plug connector by the 1/4 inch vertical ridge that extends the length of the metal barrel (firmly) and pull straight back (pop) its off, to reinstall, grab same place, fit over plug and push (pop) its on (sorry no drama)
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