the pump you are looking at is both the hand primer and the fuel supply to the IP. When the car is running, a camshaft in the IP is turning and pumping the lift pump.

The big spring is the return for that metal piston you see right next to it. You could call that lift pump piston.... I guess.

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ps - thanks for inspiring me to do this. Ive been putting it off. Please update your final conclusion if you ever figure this out.. I have very similar issues but only when the tank is low.

It might help to make a mental record of the conditions that are co-morbid with your fueling issues. (temp, fuel level, load.. etc..)

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