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FIXED !!! :D
When I saw that both the big fuel line and small vent line were both really long and not well routed, in that they went downhill from the filler neck, then back uphill to the fuel tank, I was discouraged.
I decided to tackle the easier vent line, and hope that was enough to fix the problem.. it was!
When I shortened the vent line with a hacksaw, removing the P-trap, about half an ounce of fuel spilled out, plenty enough to block the air vent.
So I took about 8 inches off, bent it to fit, and reattached it. Just came back from the Mobil station, where I filled it to the top (it was about half empty) at full flow rate, without any instances of it "clicking off"
yeah!!!
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