The old style screw-handle primer pump is notorious for causing this exact problem. If fact, there are at least a few stories on this board of cars being sold because that pump was leaking and the owner didn't know why the engine wouldn't run. I think we hear less and less about it these days because they've almost all been replaced by the new style.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References