Vapor Lock

[binzofna]

I have a problem with my 41 Cadillac.  The fuel in the bowl above the fuel pump is bubbling after a few minutes of driving and the vehicle starts to stall.  I have installed a electric fuel pump in line under the drivers seat with a switch to turn it on & of.  I am having the same problem on both my 1941 Cadillac's.  I live in Palm Beach Gardens, Florida.. Can anyone give me some ideas as what to look for. Thanks Mel

[C Gorgas]

I have wrapped my fuel lines in the engine compartment with fiberglass and have had no further problems on my '41 Cadillac. Give it a try. Chet 25441

[Bill Ingler #7799]

The majority of vapor locks occurs in the fuel line from the tank to the engine pump as well as the engine pump itself. The aux pump needs to be mounted as close to the tank as possible as pictured below on a 41. Use the correct type aux pump, one that does not cause the engine pump to work hard pulling fuel through that idle aux pump which in turn can produce low pressure in the engine pump. Combine that low pressure with heat and you can have a vapor lock in the engine pump. Airtex E 8011 6 volt is a good aux pump to use, works with either positive or negative ground. A Carter is a vain type pump and it is hard to pull fuel through a vain type pump. Attached is an old article from Cadillac on vapor locks which is an interesting read.    Bill

[Jay Friedman]

In addition to Bill's advice, I suggest you try to use ethanol-free gasoline exclusively if it is available in your area.  You can check this on the
www.pure-gas.org web site.

My '49 would sometimes vapor locking after ethanol contaminated fuel became common some years ago.  Ethanol-free gas "cured" it.   

[Lexi]

Myself and some other members use a separate dedicated fuel line for the auxiliary electric pump. I have a toggle switch for it, that is also connected to the ignition switch, so it can only be turned on when the ignition switch is on, for safety. So when the car is shut off it is also off, (no running pump & fire hazard). When the car is on it can be turned on or off. The separate line runs parallel to the factory line, then by-passes the factory mechanical pump, then "T" connects to the fuel line between the carburetor and mechanical pump. There is also a fuel filter at the electric pump. Therefore, the electric pump can be used as required (especially to fill carb bowl to expedite starting after long periods of inactivity-saving your starter motor), or turned on to combat vapour lock. I agree that it should be mounted as close to the fuel tank as possible. I have run the car this way for 2 years without a problem, using the OEM pump alone or both running simultaneously. Both rated for same pressure so as not to damage carb/flood engine. Clay/Lexi