first thot was inertia sw.,but u said can hear pump prime and stop. should then run during crank. then u said took pump apart and blu thru, dislodged something? hmm debris in tank? check valve at pump output end passes fuel in one direction.sticky? watery fuel froze? (ethanol based fuel turns watery after sitting) we used to sell BG product to emulsify and suspend water so cars could pass their water without pulling tanks. napa can get it. all the methyl ethyl kind are no good 4 injectors. if that dudn work, my pal rubs seafoam on everything as a salve. blo thru the filter, should b no resistance.dumpfilter contents(out the inlet) in a pickle jar, let separate. tells water and debris size and type. happy moteur