I had a fuel pump make a odd knocking noise in a Ford FE engine. What happened is one of the springs failed and was hung up inside the arm. When it finally spit it out it dropped into the pan, and got sucked into the pump, stopped the pump and then the shaft broke stopping the dist from turning. Not sure how it got past the screen, but it did.

Same thing happened to a friend of mine with a 351M.

Not sure if this helps, but mechanical fuel pumps suck at times.

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