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Plumbing electric fuel pump return line

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  • Fuel System: Plumbing electric fuel pump return line

    I have read many of the posts that recommend an electric fuel pump to help resolve "vapor lock" issues on my 63 Avanti R1. I bought the car with an electric fuel pump installed back by the tank and it is plumbed to an incorrect Lark-type mechanical fuel pump that has some loss of diaphragm material. I suspect that the old Lark pump may be part of my problems. My options seem to be pay $160 for a proper R1 fuel pump, pay $42 for a replacement Lark pump, or just go with the electrical pump. Since many of the posts recommend electrical fuel pumps, my question is how do I plumb the lines so that the return line still works? Do I remove the mechanical pump and install other fittings? If so, what are they? Or, leave the old mechanical pump hooked in to use the fittings even though it may not be working? Or pay the higher cost for a pump that may crap out in a few years. Thanks!

  • #2
    Get rid of the Lark pump before it starts pumping gas into the oil pan.
    I would never connect a electric fuel pump so that it pumps into the mechanical pump. The only way I would have both is connected using check valves so that one pump did not pump into or through the other.
    I don't see the need for the bypass if you only have an electric pump. Others properly disagree. You will probably need a pressure regulator with a electric pump.
    I don't know which return line connection you have; the one at the mechanical p;ump or the one near the carburetor. In either case unless someone changed something the return line should still be connected as Studebaker designed. A replacement pump should connect the same as the present Lark pump
    I have 2 Avanti R1's and both have the mechanical pump. One the modified Chrysler type (been there for 3 years) the other has the original Studebaker type and has been there for 10 years or more. I would not use any mechanical pump other then the original carter design or the modified Chrysler.
    Yes; if my car sits for more then 3 days there is no flue left in the in the accelerator pump chamber to aid in starting.


    • #3
      Thanks for your advice. The return line is connected directly to the fuel pump. I presume that is how it will be if I purchase the proper R1 fuel pump. Just so I understand my options, I was curious how people that go chiefly with an electric pump connect the return line.


      • #4
        In my opinion and many others here, on a Jet Thrust Lark, Hawk or an Avanti it is just BAD science to even think about modifying a very good Fuel System with a Very good Carter Super Pump, a "T" Fitting with a REDUCER fitting (on Avantis) at the Fuel Pump, and a Cool Fuel Return Line.

        These Carter Pumps have been known to very often Run 20 years or more and THAT was BEFORE they had the Ethanol resistant, "Rubber" replacement Parts in them.

        It would be a plumbing nightmare to Rube Goldberg a bunch of lines for the return line with the Pump at the Tank.

        In other words it is well worth it to pay more now and forget it, an Electric Pump is possibly poorly made in China and some Brands fail quite quickly.

        A Carter Super Pump BEFORE being Modified for a Stude.
        This one is NOT the Correct Chrysler Model, it's a Ford, just an example of a Super Pump.
        Last edited by StudeRich; 09-21-2019, 12:43 PM.
        Second Generation Stude Driver,
        Proud '54 Starliner Owner


        • #5
          Sounds like good advice. Thanks!


          • #6
            An important point is that the fitting at the fuel pump that goes to the return line has a restriction in it (small diameter hole). This to bleed some fuel back to the tank without starving the carburetor. Personally, I am a fan of electric pumps. The mechanical pumps are bolted up to a hot engine block and they heat the fuel as it passes through. This is a real issue at idle, as the fuel is moving through slowly. Today's gasoline compounds this problem. Bleeding off some fuel, as is done with the Avanti return line helps, but using an electric pump keeps the fuel cool until it reaches the carburetor. As mentioned above, running an electric pump through the mechanical pump is a BAD idea. Not only does it negate the advantage of keeping the fuel cool, it risks filling the crankcase with gas.
            Jim Bradley
            Lake Monticello, VA
            '78 Avanti II


            • #7
              You can go from mild to wild. The main idea is to keep fuel circulating. Using A electric pump with a fuel filter that has a small orfice port that returns to tank is the easy way.
              I guess I chose a little more toward the wild. But, being a modified car it didn't matter. I wanted to regulate the fuel pressure, and know what it was. I used a pressure regulator with a return to the tank. If you will look on my picture posts , beginning with #7 you can see the system I used.


              • #8
                Here's how I plumbed mine in. The car is a '63 R1.

                I ran a 3/8" line as per original from tank to filter to pump and the pump to the original line going forward. In the engine bay I ran a 3/8" line up from the original tube, around the engine and nearly to the carburetor's 5/16" tube. I used a brass cross as that was something I had on hand. I installed a 3/8" barb on one point and a 5/16" barb opposite. On one cross leg I installed a plug and opposite of the plug a 1/4" elbow barb pointing back to the 3/8" barb. The idea was to get this junction as close to the carburetor as possible to allow for the fuel to be as cool as possible. I also installed a 1/4" fuel filter on the return line to help add a slightly greater restriction but with the Aermotive pump that probably wasn't needed.


                • #9
                  With the issue of Vapor lock in the text it would be well to know exactly what Vapor lock is before you attempt to fix it. There has to be at least a dozen different conditions that attribute to Vapor lock. All we really know is the engine stalls, but it is not always known why and usually Vapor lock is the common term applied without knowing exactly what it is. Some years ago when all cars were carbureted and in hot weather when there was a traffic backup and many cars would over heat and the fuel would boil over and consequently stall the engine contributing to the already traffic snarl the news reporters would refer the conditions as Vapor lock, it was just a term the news guys developed. Every time a car stalled on the road it was a Vapor lock even if it was out of gas or a dead battery.

                  After a discussion with a competent carburetor repair guy we both came to the conclusion that the stalling is mostly caused by the over heated fuel boiling over in the carb into the engine and over fueling the engine. This can be the result of an engine running too hot for a multitude of reasons or a stuck closed heat riser. Many early V8 engines had the intake manifold attached directly to the intake manifold with limited space between the valley cover, on many later engines that space was increased for additional cooling. When an engine is fitted with a proper flowing radiator, clean block, head gasket not leaking, factory thermostat usually 160*, fueled and timed correctly it will not over heat. The V8 I have in my 54 Champion runs at a constant 160* even in 100* temps, I am using the original radiator and fan from the 6. Once in a while it will sneak up to 170-175 but that is as high as it has ever gone.


                  • #10
                    Can pin holes in your gas line cause the vapor lock as the gas is going through?



                    • #11
                      The pin holes in the line introduce air into the fuel system, if you have a clear fuel filter sometimes you can see air bubbles. Or the fuel filter will not fill as much and may lead to fuel starvation. Lou Cote


                      • #12
                        Hello What is the conversion to the Chrysler pump you were quoting. I have a '65 Lark 289 with a pump that has failed and a Chrysler one may be easier to get here in Australia than a Studebaker one


                        • #13
                          My advice based on my own experiences. I have done this on quite a few cars and it takes some time to set up but it solves everything. I start by deleting the mechanical pump. then I get 2 electric fuel pumps and a couple of barbed "T" fittings. I put an inline steel filter as close to the tank as I can, then a barbed "T" one side of the "T" goes to pump 1, other side to pump 2 then I tee those two lines back together. then connect to the original fuel line as long as its in good shape. Up near the carb, I put a second fuel filter (one with a vent line) like flashback said. Then just after that I put in a fuel regulator then out the regulator fuel line goes to the carb. Now I run a return line off of the fuel filter by the regulator (1/4" steel brake line connected w/unions because the only way I have been able to buy steel like is in 4 ft sticks). I run this line back to the filler neck, here it gets brazed. because its easier to put a return line in the neck than in the tank and easier to delete too if someone wants to put it back. Now I wire the pumps to a toggle switch then through a fuse to an ignition source.

                          With 2 fuel pumps I never get stranded, if one dies I just flip my toggle switch to change pumps and keep on driving. I then change out the bad pump next time I can. I rotate (flip toggle) every time I fuel up to keep fresh gas in both pumps. I never have any backflow issues.

                          The fuel constantly moving makes vaporlock a distant memory. Its always moving and if it doesn't get used it gets dumped back into all that cool fuel in the tank.

                          With the mechanical fuel pump the fuel is under suction until it gets to the hot fuel pump then for that 1 or 2 feet after. With an electrical pump right outside the tank the fuel is under pressure from the time it leaves the pump until it reaches the carb. This ethenol fuel boils at 160 degrees f. the sooner you get it put under pressure the better.

                          This system also eliminates dry starts. I just listen for the sound of fuel running in the tank then I know the carb has fuel and its ready to start. no matter how long the vehicle has been sitting.

                          good luck


                          • #14
                            Sorry should have checked spelling before post My Lark is a 63 not 65 DOH!!!