Leaky Carb

[Guest gwatkins]

My friend's '24 Business Sedan has an aftermarket fuel pump which is used on initial startup to fill the vacuum tank. I'm guessing this is because something is faulty with the vacuum tank? Once the car has been running then turned off, it's no longer necessary to use the pump to restart, but after sitting overnight the vacuum tank must drain back into the fuel tank requiring the pump so maybe there's a leaky valve. He has a 3-part article from DB Club News about the vacuum tanks so we can probably work that one out.

A related problem is that shortly after the engine is turned off the carb begins to leak and continues to do so until the carb body is lightly tapped. Is this likely a sticky or worn needle valve or seat?

Thanks for indulging these newbie questions.

Gordon Watkins

[nearchoclatetown]

If you are talking about a fairly recent article about carbs I think somewhere in it is discribed how to fix that problem. The point on the needle gets a ridge from the wear. Also the little weights inside the cap are problably worn and have flat spots on them from rubbing the float. Pull the cotter pins and turn them over to have a fresh surface.

[dwollam]

And the vacuum tank is probably loosing it's gas to the carb, not the fuel tank. sShut the valve off under the vacuum tank when not running.

[Guest gwatkins]

Thanks nearchocolatetown. I'll try your tips on carbs. The article I referred to (not sure of the date) is about the vacuum tank, not the carb.

And thanks Dave, I noticed the valve and thought that might help but if it's losing fuel to the carb wouldn't that cause the carb to leak? Once the carb is tapped, it stops leaking. If the carb is the problem, will rebuilding the carb eliminate the need for the fuel pump or is there likely a vacuum tank problem too?

I saw somewhere that you should suck (by mouth) on a tube connected to the vacuum tank to fill the tank!! Was that SOP for starting this car? If so, were fuel pumps later commonly installed to avoid this?

Thanks,

Gordon Watkins

[dwollam]

Don't suck on anything! Fumes are bad. If the carb leaks it will drain the vacuum tank. I always shut the valve off when parking the car for any extended period. (more than and hour say) If you need to fill the vacuum tank, pull the plug on the top and carefully pour gas in it. Make sure the screen on the inlet side into the vacuum tank is clean. Make sure you have no vacuum leaks and make sure the atmospheric vent (short little bent over tube) is not plugged off. An electric pump before the tank will overflow the vacuum tank. Gaskets must also be used between the top and the vacuum tank and be in good shape. Gas could not possibly be drawn from the top of the vacuum tank back to the gas tank because nothing reaches down inside the vacuum tank to make that physically possible.