Andrew wrote:
Quote:
Also, on two occasions, the car quit on me while driving at slow speeds. I had to stop and let it cool down 45 minutes before it started up again after some cranking with the pedal floored. Another time, I was in third and felt the car die. I floored it with the car still in 3rd gear and after a few jerks, it started back up and ran fine.
Most of my hands-on work on Packards has been with V8s, but this description fits "fuel percolation".
Vapor lock occurs when liquid fuel in the lines turns to gaseous vapor. Diaphragm-type pumps work because liquids aren't compressible, but vaporized fuel
IS. As a result, the engine is starved for fuel.
However, percolation occurs in the carburetor. The hot fuel literally begins to boil - foaming up through the bowl vents and down into the carb throat. The engine then acts like it is loading up or flooded.
All this is really nothing new, but modern fuels contain higher levels of alcohol and have made things a bit worse for our old carbureted vehicles.
The factory installed fuel pumps shield for a good reason; too often, the less-informed discard them in the course of routine service.
With everything else in proper working order, another trick is to "insulate" the carb from the heat of the manifold. Some manufacturers used two or more gaskets. I've recommended a a thin piece of phenolic board, trimmed same as the base gasket and then sandwiched between two if those gaskets. Those who have followed this often report success.
As this appears to be a common problem, I've held back some general info in favor of a FAQ post that I'll be working on.
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