Ok, thanks

when i replaced my primer pump... it didnt come with a new plunger and spring. now, i dont know if that plunger is supposed to be part of the lift pump, and i just accidentally pulled it out when removing the primer pump or what. but make sure that the spring and white plunger piece are installed. when i put the primer on without it, it did exactly what you describe. it would just pump and pump, never moving any fuel.

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1981 NA 300D 310k miles

These are found on the earlier style pump, like I pictured on a few posts up....it was usually only on non turbo and a few 240d's....for some reason the turbos always seemed to come with the other style pump...even in the w116 models they used this pump...its been a mystery to me why they used two different types on the same year cars..

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I'm still having problems, and never found saw any spring. Could it be in the old pump?