Light Aircraft Association

I run a VW 1600 in my Taylor Mono and the carb has developed a fuel leak. After start all is fine for a minute or two and then fuel starts to leak from the top of the float chamber; all this happens at around 1500rpm. I've replaced the float and needle (shut-off) valve, but to no avail. The Solex carb specialist tells me that the max input fuel pressure to the carb should be 3psi, but we've measured this at 7.5psi (at 1500rpm). Before we start fitting a fuel restrictor in the line between the pump and the carb does anyone there have any experience of a similar problem on this type of engine? If so any advice would be gratefully accepted.

The carb is a Solex 30AHG (as fitted to Austin cars from the late 40s to early 60s) and the fuel pump a Quiot Type Y20.

Cheers

Richard K.

Fitting a restrictor wont reduce the pressure, only the flow. You need a way of regulating the pressure down with perhaps a by-pass back to the tank.
The best alternative is to fit a pump which does the required pressure.

Possibly you're thinking of "FilterKing" who make a small alloyregulator plus a regulator that is built into a Gascolator type filter assembly for about £40.
Ebay have them

Don't be too hasty! Your pump should not be putting out this much pressure and placing a restrictor into the line may put excessive strain on the whole thing. If you have a mechanical pump check that you have the right gaskets and spacers in between the pump and the engine. The pump works off a rod-plunger and onto a cam, if you have a small spacer the pressure will increase due to the rod-plunger moving up and down more. Hope this helps...

Facet 40105 pump runs at low pressure (typically 1.5 psi on my Healey) but I wondered if it was possible to put the pump low in the cowling so that it pumps uphill by a foot or so, thus dropping the perceived pressure at the carb when running in the same way that my upstairs taps run a lower pressure than the taps in the kitchen. Not sure if I am quite up to speed on fluid dynamics, though!


PS I checked my 40105 collection and they all have the white nylon valves, so I'm OK. Non-return valves are available for about £6-8 on ebay in 6,8 and 10mm bore.

Hi,
Have you checked the float needle seat is sealing in the carb'? If the (usually brass) needle seat is not fitted with a fibre or alloy gasket washer the fuel will leak past it and give you unregulated flow, even though the needle is fully seated.
Another possible cause is engine vibration making the fuel throff (if that's how you spell it!) and allowing the fuel to leak from the float chamber.
Most VW type engine driven pumps will only manage 3-4psi, may be worth checking the gauge accuracy?
Neil