Fuel leaking from carburettor vent

Mick Rae said:
I replaced both the float and it's spindle as the spindle was a bit secondhand looking! Old float didn't have and fuel inside,but I figured replace everything and hopefully not have to go there for a while :thumb:
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Yes, although I am pretty sure the carb has never been messed around with (it's a family car, from new), and there was no fuel in the float, it seems the logical next step to get a replacement float and spindle.
 
Now I am completely confused. After putting the car away Friday evening (with it still leaking), I had to move it this afternoon (Sunday). Thought I'd check the status of the leak - hmm, no leak (after running for a couple of minutes).

Put car away again, and came back about four hours later. Pulled it out of the garage, let it run for a while, and… no leak. Let it warm up, pushed the choke in, no leak. Left it ticking over for about 20 mins, no leak. Drove it up and down the garage forecourt a few times, no leak.

I suppose this is the nature of intermittant faults, but it is a little bit maddening.

I will order a new float and fit that anyway, and see where we go.

Just to note, even though the car had been running for about 25 mins in total, the carburetter was still relatively cool to the touch - I suppose all that fuul running through it acts as something of a coolant.
 
typonaut said:
Just to note, even though the car had been running for about 25 mins in total, the carburetter was still relatively cool to the touch - I suppose all that fuul running through it acts as something of a coolant.
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You’ll get a lot more heat in the engine bay when the can has been driven. A working engine produces a lot of excess heat (hence why the choke goes in very quickly when driven but takes longer when left idling.
 
sdibbers said:
You’ll get a lot more heat in the engine bay when the can has been driven.
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Well, it is a bit of a moot point at the moment, as I don't think it is reasonable to drive it without at least changing the float (it seems improbable to me that this is the issue, but…). My experience with cars is that driving, if the cooling system is working, usually has the effect of reducing engine temperature - because you are getting more fluid through the circuit and more air through the radiator. Indeed, revving the engine while stationary in a hot car will have the same outcome.

However, I recognise that reducing the engine/coolant temperature is not the same thing as reducing the ambient temperature in the engine bay - so a cooler, driving engine may result in a warmer carb.
 
I would want to know what the fuel pressure was at the carb. Make up a T fitting to go in the line and try to get a reading when the engine is running at various rpm.
HIF carbs do not like excess pressure, keeping them fed with under 3psi at all times keeps them happy.
If someone has fitted an electric pump in place of the stock mechanical one without fitting a regulator, then it will flood all the time.
 
typonaut said:
However, I recognise that reducing the engine/coolant temperature is not the same thing as reducing the ambient temperature in the engine bay - so a cooler, driving engine may result in a warmer carb.
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Precisely, its ambient under bonnet temperatures that are your enemy in this circumstance.
 
These carbs need overhaul sometimes, leakage is common when parts are become bad like floater pin,
or dirt is in that pin cause it not to close..
 
cobraboy said:
I would want to know what the fuel pressure was at the carb. Make up a T fitting to go in the line and try to get a reading when the engine is running at various rpm.
HIF carbs do not like excess pressure, keeping them fed with under 3psi at all times keeps them happy.
If someone has fitted an electric pump in place of the stock mechanical one without fitting a regulator, then it will flood all the time.
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This car does not have an electric pump – it has the original, glass-domed mechanical pump. it also has the original pump to carb pipe – which has screw fixings at each end and is fairly stiff.

So, to make up a t-piece I probably would have to source some fittings to fix on to the pump/carb with a standard length of fuel hose, etc.

While the idea that it was the pump producing too much pressure did occur to me, I think this is not the case, because when the carb is leaking, I can use the primer on the bottom of the fuel pump to continue that leakage when the engine is not running.

Just an additional note – as I previously posted, this car has been laid-up for 25 years, and prior to that it was all working as expected. So, the only thing that has changed in that time is that it would previously have been running on leaded (or lead replacement) fuel, and now it's running on unleaded E10.

I have serviced the carb with the SU service kit, so all new seals/gaskets - shouldn't be problems there. There was also no dirt or grit in the fuel bowl, so not obvious why it started overflowing, and continues to do so. Oerall, any impediment caused by 25 years of standing idle should have been cured.
 
kees66 said:
These carbs need overhaul sometimes, leakage is common when parts are become bad like floater pin,
or dirt is in that pin cause it not to close..
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I have ordered a new float - but nothing appeared to be wrong with the existing float (no fuel in it). The float pivot is clean and unmarked - the float pivots on this fairly loosely, so I cannot see that being a problem.

I am wondering whether the new float will come with a little cardboard float setting gauge - that's what you usually get with service kits (at least for my other car).
 
typonaut said:
I have ordered a new float - but nothing appeared to be wrong with the existing float (no fuel in it). The float pivot is clean and unmarked - the float pivots on this fairly loosely, so I cannot see that being a problem.

I am wondering whether the new float will come with a little cardboard float setting gauge - that's what you usually get with service kits (at least for my other car).
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Then the little needle do not seal off, just a little wear is engough to let it leak. I had this with a 2200TC where on carb did overflow. renew the float and needle did cure that.
 
kees66 said:
Then the little needle do not seal off, just a little wear is engough to let it leak. I had this with a 2200TC where on carb did overflow. renew the float and needle did cure that.
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The needle valve and seat have been replaced, which apparently did not resolve the problem. I am waiting for a new float to arrive – but I honestly think there is nothing wrong with the old one.
 
typonaut said:
The needle valve and seat have been replaced, which apparently did not resolve the problem. I am waiting for a new float to arrive – but I honestly think there is nothing wrong with the old one.
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Very strange, because when fuel get in the float go up and close, so two things, or there is a crack in the carb, or the float needs adjustment, sometimes it need to be bend a little so the little valve can close. somewhere it leaks, and it is normally not difficult to find. The height float is important, if it is to much then or there to little fuel or it over floats. Normally when do a overhaul, parts of the whole carb needs to be renewed.
 
Hi, It may be that the float valve is not sealing, Just give it a couple of turns with a little pressure to kind of lap it in. The Viton tipped ones are better at sealing but not immune from a little bypass.

Colin
 
The needle should be Viton tipped, solid brass ones are dodo material. The Goss needle & seats are good, using a ball to seal, but some folks have had sticking problems with them too.

Yours
Vern
 
Yes, it is Viton tipped (can you buy solid brass ones anymore?). I have just fitted the new float, I set it to cut in a little earlier than the manual suggests - so perhaps this will cure it. I've driven it a couple of miles down the road and back, and no leaks so far… But that's how it was before… until it started leaking again.
 
typonaut said:
Yes, it is Viton tipped (can you buy solid brass ones anymore?). I have just fitted the new float, I set it to cut in a little earlier than the manual suggests - so perhaps this will cure it. I've driven it a couple of miles down the road and back, and no leaks so far… But that's how it was before… until it started leaking again.
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Then somewhere float house is cracked or there is dirt, leaks around the needle seat or the needle do not work well, these can also stick. JUst replace them to.
 
kees66 said:
Then somewhere float house is cracked or there is dirt, leaks around the needle seat or the needle do not work well, these can also stick. JUst replace them to.
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Yes, all the parts have ben replaced: float, needle valve, valve seat, jet, jet seal, float chamber seal… We'll just have to see if it now stops the leak. There is no dirt, and I am pretty sure there are no cracks.
 
typonaut said:
Yes, all the parts have ben replaced: float, needle valve, valve seat, jet, jet seal, float chamber seal… We'll just have to see if it now stops the leak. There is no dirt, and I am pretty sure there are no cracks.
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Maybe the gasoline get to high in chamber, so just bend the floater a little so it keeps needle closed. Or something is wrong with carburetor piston needle, More tips I do net have, I do not now.
 
kees66 said:
Maybe the gasoline get to high in chamber, so just bend the floater a little so it keeps needle closed. Or something is wrong with carburetor piston needle, More tips I do net have, I do not now.
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I had the exact same symptoms, until I beefed up the heat shielding below the carbs. Modern fuels are far more volatile and boil at a lower temperature than old petrols. Mentioned this earlier in this thread.
 
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