Dry carburetor

[rgshafto]

I've got two '36 sixes, both with original 324 Carter carbs. If I leave the coupe sitting for a week, I'll have to crank like hell to get gas back to the carb. Often it takes priming to get it to go. But I can leave the cabriolet for a week and it will start with relatively little cranking. So my coupe carb is going dry, but how? It doesn't seem to be leaking. It has always done this (since I got it in 1965), so I wonder if the fuel is getting siphoned back through the fuel pump diaphram? Leaving the tank full does seem to help.

When I was kid, I remember my father flooring the gas as he turned off the key, claiming it would make the car easier to start next time (he used that car infrequently).

Any ideas?

[50s cars]

I have the same problem with my 51. I cured it with an electric fuel pump. Some people run it through the mechanical one, something you can do if you have a manual switch to turn the electric one off during normal operation. You need the mechanical one for the vacuum it provides, but I totally bypassed the fuel part with my electric because I do not want to pump raw fuel into the crankcase in case of a diaphram leak.

[rgshafto]

Yes, I've had an electric pump on it in the past, between the vacuum pump and the carb, but never liked the looks or the sound of the thing. Maybe the new ones are quieter? Since only one car does it, there must be something going on in the fuel system itself. Not a big deal, but I don't really like to prime it either, fearing the too much fuel will wash the cylinders of oil, increasing wear.

[carbking]

The fuel is probably evaporating through the vent. Why does one do it and the other doesn't??? Different amount of heat seen by the carburetor.

(A) possible stuck heat riser valve

( possible different valve thermostat

© possible different exhaust system

(D) even possible one engines paint holds heat better than the other

A leaky fuel pump valve might allow fuel in the lines to drain back to the tank, but NOT from the carburetor.

Jon.

[rgshafto]

The heat riser valve doesn't have the return spring on it anymore, so that sounds like a possibility. This carb is 1" higher off the manifold that the other though - a spacer to prevent vapor lock, so doubt if that's the cause.

Thanks for replying.

[rgshafto]

Well, I found the fix for this problem. The original style fuel lines can leak air, but not gas. When porous to the air, they allow the fuel to leak back to the gas tank and diminish the suction the fuel pump can provide. I replace mine with modern fuel hose and the problem has gone away. Nice to find such an easy fix.