From my experience - once you are in the right spot - that point right between open and closed - you will not need to pump the primer to get 1 drip per second.

If you are off and the valve is too open you will need to keep pumping to see fuel flow through. So to get to the right spot i needed to have an assistant keep pumping while rotated the pump.

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car