Topic: Vapor lock in my '48 flathead


carducci7    -- 08-14-2015 @ 10:04 AM
  I think I may be experiencing vapor lock in the 1948 Ford V-8 I just bought. Car ran for about 7 miles on a warm day, then stuttered several times and then stalled as I was driving it. Once it stalled, I could not restart it. But when it coloed down, it started up again.

Is this vapor lock or possibly water in the fuel lines?

If it sounds like vapor lock, any suggestions for a remedy?

Thanks


cliftford    -- 08-14-2015 @ 3:57 PM
  I had the same problem with my '48 during hot weather. I added an electric fuel pump ahead of the original one and it took care of the problem. The ethenal gas we're getting tends to vaporize at a lower temperature. This is also a classic symtom of a bad or failing coil coil or maybe condenser. It's hard to say which, but I would try a different coil first.


Old Henry    -- 08-14-2015 @ 4:29 PM
  One test that has worked for me to identify vapor lock as the problem is to take along a gallon of water. When the engine dies, get out and pour the water on the fuel pump and fuel lines for a while to cool them. If it starts up after that it's vapor lock. That's how I ultimately diagnosed vapor lock in my 47 and put an electric pump in to solve it.


carducci7    -- 08-15-2015 @ 8:30 AM
  Very helpful information; thank you!

Tom


carducci7    -- 08-15-2015 @ 8:32 AM
  Very helpful about pouring cold water over it; I've heard about that elsewhere but you confirm it. Also like your idea of the electric fuel pump.

Tom


supereal    -- 08-16-2015 @ 7:11 PM
  Vapor lock is often blamed for your problem. More often than not, it is caused by a failing coil when hot, or a partially blocked fuel line from the tank to the firewall.


TomO    -- 08-17-2015 @ 7:19 AM
  That is a very nice looking car.

You don't have to wait until you are in need of a flatbed to find out where your problem is. Just a couple of simple tests will give you a good idea.

First check your spark. A weak coil or condenser will act the same as vapor lock causing the engine to die when hot. You should have a good blue spark, 1/2" long at idle when a plug wire is held near a head nut or other ground source. If the spark is orange colored or less than 1/2", change the condenser and retest.

If you have good spark, check your fuel delivery. To check fuel delivery, you need a graduated 16 ounce or larger container to determine the amount of fuel delivered in a measured time. Disconnect the fuel pump line from the carburetor and direct it into a graduated container. Crank the engine long enough to get 2 ounces of gas in the container and then continue cranking for 15 more strokes of the pump. The pump should have delivered 6 more ounces of gas.

Insufficient fuel delivery can be caused by a vacuum leak, plugged flex line, worn pivot in the pump arm, stretched diaphragm, plugged fuel line or tank pickup, plugged tank vent or wrong gas cap or a worn push rod. The push rod should be 8 7/8" long for the cast iron manifolds and 7 7/8" for the aluminum manifolds. The travel is about 3/8".

If both the spark and fuel delivery are good, check the fuel pump output pressure with a vacuum gauge that has fuel pump pressure markings on it. You should have between 1.5 and 3 lbs of pressure at the output of the pump. This will keep enough pressure in the line to keep the fuel from vaporizing in the line.


Tom


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