Su carb

[Foofighters 27]

Hi please see photo ,could anyone tell me why fuel sometimes comes out of here??
Thanks mark

 

[malcolm]

That's the overflow. Wear or dirt in the fuel inlet valve opetated by the float would be the most likely reason. Otherwise punctured or badly set float.

 

[Foofighters 27]

Hi thanks for that ,so where would I find the float ,another thing ,when I pull up at lights or come to a stop ,the engine is reving really high ,would the float have something to do with this ??
Thanks mark

 

[bison]

If it's only revving at tickover then it sounds like an air leak. Check all the nuts are tight and the vacuum advance take off isn't open to the atmosphere. This car still has the original distributer which doesn't have a vacuum advance. Check the throttle cable isn't hung up. Check the choke is going off/opening completely
As previously posted, sounds like you have dirt in the needle valve or a sticking float causing fuel to overflow.
Alan.

 

[bison]

Just had a brain fart. This is Lulu isn't it?, gold colour Scottish car?.
OK, it's done this before when it was really hot in France. Here's my theory. You see that fuel filter on top of the rocker cover?, when the engine stops I think the heat, which isn't being wafted away any more, causes the air/gas trapped inside the filter to expand and pushes petrol into the float bowl and causes it to overflow. Solution, remove fuel filter and just have a plain tube going from the fuel pump to the carb.
Tell me if that works please.
Alan.

 

[chudson]

air/gas trapped inside the filter to expand and pushes petrol into the float bowl ?

is it possible with the needle valve in the float bowl ? Besides the amount of air in the filtr is small so the pressure wouldn't be high and fuel temperature differences while driving and right after stopping niether.


If the revs go down after a while I would rather look for air leaks on throttle stem

 

[Foofighters 27]

Thanks guys ,yes it is lulu ,I'll have a look at the things you've mentioned ,fingers crossed she's coping well with the hills of North Yorkshire ,I've also found the speedo needle works in reverse ,,so maybe an angle drive would cure this ,I've looked behind the actual speedo ,and there is room to attach one .any ideas ??
Thanks mark

 

[bison]

We were in France, Lulu had the stock carb fitted with the fuel filter in place, it would flood occasionally for no reason or so it seemed, I removed the fuel filter and replaced it with a bit of pipe, no more problems?. Unlikely I know but it was the only thing I could think of, there was nothing wrong with the carb, I put the carb from my car on it and it did the same thing, it never happened on my car, no filter. I suspected the fuel pump so replaced it with a new old stock one, still flooded now and again. When the SU was fitted the filter was then put back on, this is the first I've heard of it happening again.

Alan.

 

[Foofighters 27]

Thanks Alan ,so at the moment I have to clean the fuel filter out every couple of week ,it fills up with sediment ,probably from the fuel tank,so you think it would run better without the filter???
Thanks mark

 

[bison]

Interesting. If it's that mucky then it probably is the needle valve in the carb float bowl that's getting a little bit of grit or similar on it and that's what's causing the problem. I don't remember the previous owner having that problem, even when running the tank low. I seem to remember the fuel pump having a little filter in it?, perhaps the other forum members can confirm that?.
Sounds like you might have to have the tank cleaned out?.
Alan.