<VV> Dribbling YH

[Smitty]

> From: Frank DuVal <corvairduval at cox.net>

> I have no idea why a regulator would help gas dribbling after shutoff.
> Since when would gas pressure be higher with the engine off? It should
> be the same, as gasoline pressure is developed only by the spring in the
> fuel pump, not the stroke. Many people can not grasp this concept...
>
> If you are thinking the heat of the shut off engine is raising the
> pressure, then what is the regulator going to do? It can only limit the
> flow of gasoline from the fuel pump into the gas line between the
> regulator and the needle/seat/carb inlet. If the engine is shut off, no
> gas flows. Therefore no regulation.
>
> It's not like the regulator spits out the excess pressure through a vent
> hole. That would be exciting!
>
> The return line system used on turbos and late late production adds
> another wrinkle to the normal system described above. The return line
> VENTS the gas line from the fuel pump to the carb/needle/seat. So, when
> you shut off a normally plumbed turbo, the gas line pressure between the
> fuel pump and carb drops to ZERO. So what will a regulator do? 
> Nothing.....
>
> Unless you plumb the regulator between the fuel filter and the carb, in
> which case the line before the carb might not vent through the return
> line, thus causing a problem, not fix one.
>
> So, if the fuel line pressure drops to zero (make sure the return line
> is clear back to the tank) and gas still drips in the carb, the fuel
> level in the carb is where I would start troubleshooting.
>
> If the accelerator pump has a hole in it, the symptom will be rich
> mixture at idle. Then as the hole gets bigger, rich at speed too.
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Looks to me as though you pretty well said it all Frank
One thing I might add about dribbling.  I have looked at the internal 
circuitry of YHs and I don't see the logic of it but I have seen the 
dribbling stopped by ensuring the accel pump check ball or check needle is 
seating properly.  (Depending on which carb you have).  Stick a small flat 
face punch down into the hole and tap the ball or needle into the seat. 
Smitty