I would start at the bottom of the hose. Sometimes road debris gets into the end of it and clogs it. Easier maybe that getting to the end in the box.
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Ian Lomax - Current: 1973 Berlina, 1984 GTV6, 1987 Milano Platinum "racecar"
Past: 71, 74 Spiders, 2x 74 Berlina, 74 GTV, 76 Alfetta GT, 88 Milano 3.0, 97 164LS