Originally Posted by
tomatofiasco
the standard carb is vented too, with two big holes bored in the top plate over the float chamber. i know this from when i turned one upside down and got wet. my carb is really crusty and not at all new but the car starts up, whatever the weather, even if its been a week in the sun, with about 2-3 cranks on the second choke detent. i have heard my fuel pump run when i turn the key to ON, so i guess the chamber evaporates a little bit of fuel and needs topping up.
just puzzling it out, none of the jets can drain from gravity alone. the accel pump, if its at all like the keihin carb, is at the bottom corner and often leaks, but this is really really obvious because there will be a clean area below it, on the heat shield or whatever, where the petrol has dripped. it also smells like a Caltex HQ whenever you return after having parked.
on the standard carb theres an idle jet, right at the bottom lip of the carb body below all the butterflies. directly behind it, protruding from the carb is the idle mixture screw, and directly above that is the shutoff solenoid. this is spring-loaded shut and magnet retracted. i assume your weber has one similar, and if it didn't return properly it might cause overrun backfiring and, depending on the plumbing, allow fuel to bleed out when the engine was off. fine channels might also have a capillary effect.
its interesting that others are reporting a similar period before the car wont start, it suggests to me a uniform-ish rate of leakage, so perhaps its a similar or identical problem in most cases, metering out fuel at a similar rate into stationary engines of about the same capacity...
or, not.
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