If it was me, knowing that small critters had gotten to the car, I'd start at the beginning. Get some fuel jugs and siphon as much fuel out of the tank as you can. Pull the tank bottom plug and get the gunk out. Pull the tank strainer and get the gunk out. Find the tank vent (if there is one - may be vented through the cap) and get the gunk out. All need to be done to a high mileage car that you don't really know the history of. Then take the injector pump to an injector shop you can trust, meaning make them show you their books for YOUR pump. And remember to put new gaskets in the tank plug and strainer.

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daBenz - 1970 220D