Fuel leak from carb

[Rubbledog]

Hi everyone
Hope someone can help, have recently bought a pearl cabriolet which after a few days in the garage would not start, I have sorted the starting problem including rebuilding the fuel pump and she started first time today! Problem is when the engine is turned off there is fuel leaking from the carb Venturi. I have stripped the carb and all seems ok, but the fuel leak is still there, anyone have any ideas?

[Nigel was in Brittany]

I had the same problem with mine ,itturned out to be the emulsion block being porous .

[Zetomagneto]

Hi everyone
Hope someone can help, have recently bought a pearl cabriolet which after a few days in the garage would not start, I have sorted the starting problem including rebuilding the fuel pump and she started first time today! Problem is when the engine is turned off there is fuel leaking from the carb Venturi. I have stripped the carb and all seems ok, but the fuel leak is still there, anyone have any ideas?

Fuel level too high in the float chamber? Pinhole in the float?

[Peter Clayton]

Not unheard of my RP had a small drip on stopping the engine. If the leak is more than that that try checking your float height it my be too high.

[Ruairidh Dunford]

I agree with Peter - it is not uncommon, if it is just a few drips.

[Rubbledog]

Sorry about the delay,thanks for the suggestions,I know the float is ok so I'm going to try the float hieght in the next week or so, (I am away from home at the moment). Hopefully this will sort the problem, if not I will probably look into fitting a S U carb.thanks again and will let you know the outcome.

[Colin Wilks]

If the float is too high surely you would expect over rich running from the off due to flooding, not just a drip when stopped? I am new to sevens but had this rich running problem on my land rover's Zenith 36IV - after rebuild the float turned out to be 1.5 mm high (4.5% out). Here I would be thinking about more oomph from the newly rebuilt pump and a sticky or worn needle valve.

[Peter Clayton]

Sorry about the delay,thanks for the suggestions,I know the float is ok so I'm going to try the float hieght in the next week or so, (I am away from home at the moment). Hopefully this will sort the problem, if not I will probably look into fitting a S U carb.thanks again and will let you know the outcome.

Not that I needed to rectify the fuel weep on stopping, but I decided that fitting a SU in place of the Zenith would be a positive upgrade. Having an ex Mini carb (1.25) I thought may as well see if it will operate, I've seen reports of others fitting them so gave it a go. I manufacture a manifold adapter to rotate the mounting bolts to suit and increased the manifold inlet diameter to as large as practicable . I checked which needle/spring combination would be best to start with and fitted an"AN" needle with the existing spring. The engine fired up instantly and gives improved torque and acceleration . No idea of fuel consumption but spark plugs would indicate correct mixture.

[Robert Leigh]

Sorry about the delay,thanks for the suggestions,I know the float is ok so I'm going to try the float hieght in the next week or so, (I am away from home at the moment). Hopefully this will sort the problem, if not I will probably look into fitting a S U carb.thanks again and will let you know the outcome.

Not that I needed to rectify the fuel weep on stopping, but I decided that fitting a SU in place of the Zenith would be a positive upgrade. Having an ex Mini carb (1.25) I thought may as well see if it will operate, I've seen reports of others fitting them so gave it a go. I manufacture a manifold adapter to rotate the mounting bolts to suit and increased the manifold inlet diameter to as large as practicable . I checked which needle/spring combination would be best to start with and fitted an"AN" needle with the existing spring. The engine fired up instantly and gives improved torque and acceleration . No idea of fuel consumption but spark plugs would indicate correct mixture.

I suggest you make sure you are using a light blue spring, the weakest available. I think Minis generally had a slightly stronger one. The AN may be ok, but the best way to get economy is to go for something weak (a thick needle), and try going thinner until any problems disappear. SUs can give what seems satisfactory performance when the adjustable bits are giving too rich a mixture, because it easy to adjust the needle to a good tickover, and if it runs ok at higher revs you don't worry, but you may be passing far more petrol than you need.

[Rubbledog]

Hi all I have at last found time to look at this problem, I have fitted a new emulsion block gasket, new float valve and under the valve I have fitted the thick and thin washer that came with the valve thus lowering the float level. Took the car out twice today and found no fuel leak when the engine was turned off, so fingers crossed the leak seems to have been cured. Thanks for all the suggestions and hope this may help anyone with the same problem.