Vapour lock

[simonandjuliet]

Anyone any suggestions for curing a vapour lock on a small engined car ?

Problem - constant flooding even when the engine turned off - petrol overflows down the choke and out of the spindle. Difficult to start when hot and stinks of petrol !

Attempted cures so far - new carb, new new carb (both with floats correctly adjusted) moved fuel lines away from head (? too hot) , changed fuel filter, removed and refitted the gaskets using hermatite and good insulator gasket.
All properly timed etc

Any other ideas ?

Thanks

 

[alewis]

Is this one of the items covered in the supplements to the workshop manual ?

(Will have to dig it out but they put a return line past the fuel pump with a restrictor I seem to think)

 

[Steve Hennessey]

Does the petrol cap have a vent? If so, is the vent blocked?

 

[politeperson]

Still sounds a bit like the float.

I would take the top off the carb and blow through the fuel inlet whilst moving the float up and down to check the action of the valve.

Are the fuel lines on the right way around to the fuel pump? One supply, one return. You could blow through the return pipe to check is is not kinked or twisted.

James

 

[Steve Hennessey]

Does the petrol cap have a vent? If so, is the vent blocked?

I have seen this happen before as the tank can build up pressure inside so it won't take long to ascertain if this is the cause!!

 

[simonandjuliet]

Thanks

Had not thought about the fuel breather ...

Have blown through all the pipes, jets and castings on both carbs.

Funny thing is that it used to be fine and then one day it started to flood ! It is my old van that I use everyday and it still works, it just uses a lot more petrol and now the new van is ready, I thought I'd try and get to the bottom of it !

So any other suggestions ?

Thanks again

 

[pepper]

I get this the other way round in my camper, if we fill right up with fuel, it can block the breather and we end up misfiring all over the place as the fuel pump attempts to turn the tank inside out.

Stop camper, release pressure and off we go again.

It's not normal for a blocked breather to cause overflowing, but it could do due to the different climate you have over in sunny France.

 

[benchseat]

There was extensive correspondence about this in a Thread entitled "Carburettor Overheating" about two years ago. It seems to be an endemic problem with early 845cc models fitted with Zenith carbs.

 

[simonandjuliet]

Useful ideas

Thanks for your comments, have found the original threads - had looked but not with the right phrases !

I was sure I was not the only one to suffer this affliction, strange because it came on suddenly - will try some of the suggestions tomorrow

 

[malcolm]

Are you using an in-line fuel filter? I've only ever had flooding like that due to a dirty seat to the float chamber valve due to frog hairs in the fuel (surely not cat hairs). They come right back after you've cleaned the valve out. Inline filter sorts that.