Float chamber

[morrisminor]

How long do you think it would take for the float chamber to empty once switched off, left it a week ,crank over on handle ten times still takes ages to fire,  bowl still empty, manually fill bowl fires instantly., once warm starts first time every time,  any ideas ?

[Howard Wright]

Hi

Give us a clue.... Gravity fed tank or pump?  What carb?  

Cheers

Howard

[Ian Williams]

So many variables affecting fuel evaporation in the float chamber, ambient temperature being a big one, try fitting a fuel pump with a priming lever then you won't need to wind the engine over by the crank. That said the hand cranking will not just prime the float chamber it will also fill the empty oil galleries prior to starting which is no bad thing.

[morrisminor]

It's a 26va , 37 Ruby

[Howard Wright]

Hi

Sounds like you may have a leak either at the pump or back to the tank.  Although the float chamber should remain full unless the carb is also leaking. 

 Is there any sign of leaking petrol?

Have you tried suspending tin cans below the carb and pump? These often catch drips and give some indication where leaks may be. 

Cheers

Howard

[Reckless Rat]

I would investigate the state of the fuel pump and the lines between the tank/pump and pump/carb.

[morrisminor]

Gone to it this morning,  float chamber bone dry,  primed it, starts first time, odd though, can't see any leaks

[dickie65]

Hi,
The Zenith Carb suffers from heat soak once the engine has been switched off which in turn accelerates the fuel evaporation.
You will find also find that fuel will drip out of the emulsion block into the manifold.
A Tufnol spacer could be used between the carb and manifold to slow down the heat soak.
If you have weak springs and dirty valves in the fuel pump it will make priming slower and allow fuel to drain back down into the pump from the pipe to the carb.
You are unlikely to have a leak from the float chamber but possibly the emulsion block gasket is failing which will allow petrol to seep out.
If the copper fuel pipe is too close to the exhaust you will have problems as well.
As far as my experience goes its perfectly normal having been involved with 7's since the 1970's

[morrisminor]

Thanks for that,  where can you get a spacer from ?

[David Stepney]

My RP saloon has had the same problem since day one. The petrol in the float camber disappears over night. The amount it loses depends (it appears) on the temperature in the garage. I have developed a cold start procedure: Prime the carb on the pump priming lever, turn the engine over a couple of times with the ignition off to prime the cylinders, ignition on, choke out and pull the starter and the engine is running by half a revolution. It seems to be a Zenith carb thing. Both the RP saloons that i have owned did the same thing. The only one that didn't was my special but that was running on 2 Solex downdrafts from a sidevalve Reliant.