My car has been running rough ever since I replaced this bolt I have adjusted it with the car running until it smoothed out. My question is about the o-ring that is on the bolt is this to keep fluids from leaking out or seal it from sucking air, could this be my problem? Thanks for any help

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84 300 Turbo / 320,000
96 E300 D / 55,000

It is a simple seal the keep the lube oil in the injection pump from leaking.

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Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section