Dome on fuel pump

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  • #11747

    I found this interesting and thought I would share what I found.

    I just figured out what the dome is for on the Jetfire fuel pump inlet line. It is something I always wanted to look into and decided tonight to figure it out. The only place I could find information was from former patents. I always assumed it had to do with surging from the pump but could not wrap my head around why. With the Jetfire having a higher pressure pump and return line back to the tank and also the use of more fuel under boost conditions I am sure this is why they decided to add it to the Jetfires. Our automatic car is missing it and don’t have a problem but I am sure it could have problems if I was hot ridding it all the time. This is not a patent for the specific setup on the Jetfire but still the same thing. Here is what the patent has to say.

    “fuel pump operates from an eccentric on the valve cam shaft on four cycle combustion engines. The rise of the cam shaft eccentric causes gasoline to be sucked into the pumping cavity of the fuel. pump itself through the action of rocker arm and linkage. On the return stroke of the cam shaft, the fuel is delivered to the carburetor. The same cycle repeats itself with rotation of the cam shaft. The usual installation requires a length of intake tubing of approximately twelve-foot length. Due to the fact that the intake stroke of the fuel pump is positive, it is necessary for the diaphragm to start to move the entire length of fuel in the intake fuel tubing, and stop as directed by the lift of the eccentric on the cam shaft. This interrupted flow causes momentary high negative pressures on the fuel in the intake line. It has been common practice to provide an internal air dome somewhere in the suction side of the fuel pump. This acts as a surge chamber. The surge chamber permits more uniform flow of fuel on the intake side of the fuel system and especially in the intake tubing. These internally constructed chambers permit the fuel to continue moving forward toward the fuel pump even though the pump has entered the delivery portion of its operating stroke. They also provide readily accessible supply of fuel and this plus the air within the surge chamber itself permit the fuel pump to deliver more fuel and reduce the peaks of negative pressure which tend to cause vapor formations in thenow commonly used highly volatile gasolines.

    Certain fuel pump designs now in common use have omitted the above-mentioned internal surge chamber and as a result of the omission, these pumps are quite prone to excessive noise due to hydraulic hammer within the intake line, they are quite prone to causing vapor formation, they do cause excessive stress to be forced onto the entire pumping mechanism and especially the flexible diaphragm.

    Accordingly, it is an object of the present invention to overcome the above difiiculties by means of an air dome serving as a surge chamber which may be readily inserted in a fuel line.”


    I wondered about that myself. We have the two 62 Cutlass converts and one has this pump with a return line and the other the pump with the attached filter bowl and no return line. The one with the return line is a later 62. Sounds like a good set up.

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