Is the rough idle with tank @ 1/2 way mark repeatable? It may be coincidental. Do you have vacuum in the tank? Open the filler cap when 1/2 full, if you hear a swoosh, you have vacuum. Do you have good clear lines on the return to see air bubbles? Are there any?

Replace the primer pump! You spill a lot of expensive fuel using the old primer pumps! I have a barely used new style primer pump from my 240D if you want to put one in. I have new washers also. I'm in Queens.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked