Weber 40 fuel leak

[MartinH]

My 67 S3 convertible has been running fine all summer, but today I noticed it spitting back through the webers. It then started running very rough. When i pulled over to check, there was fuel pouring out of the air box. Fortunately I was in a super market car park and was able to buy a spanner and screw driver. Took the air box off and cranked the engine and fuel was pouring, I mean really pouring out of the rear trumpet on the front carb. Took the top off the carb suspecting stuck float, made sure it moved ok and screwed it back together. No fuel leak on start up and managed to drive home with a small amount of spitting back and no further fuel leak evident. The car pulled fine and seemed almost back to normal.
In anyone's opinion are the onset of spitting back and the fuel leak related?
What should I be doing to avoid a repeat of the fuel leak?
Thanks in anticipation
Martin

[mbell]

I'd be checking the fuel level in the carbs. Sounds like they are over filling for some reason.

[denicholls2]

are the onset of spitting back and the fuel leak related?

Yes, they are.

Outside of the general condition of the float valves, a likely cause is dirt locking the valve piston. You might want to consider better filtration. And If your electric pump isn't regulated, it ought to be because a regulator is a lot cheaper than the consequences of igniting a pool of gasoline.

In the U.S., gasoline has all kinds of garbage in it that was never there decades ago. Likely due to the government forcing oil companies to put ethanol into it to make it more expensive and less efficient in the name of a nebulous benefit that is not gained.

[rgh0]

If its only one throat in the rear carb that is leaking fuel have a look at the location of the two venturi bodies in the carb throat . The main fuel feed passage is though the outer of the venturi bodies to the inner auxillary venturi and if this is loose due to a loose locating spring fuel can leak out around it.

cheers
Rohan

[MartinH]

are the onset of spitting back and the fuel leak related?

Yes, they are.

Outside of the general condition of the float valves, a likely cause is dirt locking the valve piston. You might want to consider better filtration.

I think you have nailed it. I was running on fumes at the time and was probably sucking up dirt from the bottom of the tank.
I am still running a mechanical pump but note your comments on filtration.
I will give the system a good clean.
Thanks for the advice
Martin