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  • Fuel System: Electric/Mechanical fuel pump combination

    Can a mechanical fuel pump be used in conjunction with an electrical pump to be used as a back up on an R2?
    Lou Van Anne
    62 Champ
    64 R2 GT Hawk
    79 Avanti II

  • #2
    Functionally yes but it’s not a very safe option. One of the failure points on a mechanical fuel pump is the diaphragm. When that fails the engine will stop running reasonably quickly due to a lack of fuel supply to the carb. Flipping on an electric fuel pump will probably feed the carb fine but will also push fuel through the torn diaphragm which in turn will fill the crankcase with fuel. Best case it ruins the engine, worst case well that involves the smell of burning fiberglass.

    Going exclusively with an electric fuel pump is probably the most reliable option but has its own safety issues as will. A stuck float needle valve won’t present a safety issue with a mechanical fuel pump as the engine would most likely flood and stop. In that scenario an electric fuel pump could continue to empty the fuel tank until the ignition was turned off. The work around for that is a low oil pressure switch that only allows the pump to start when minimal oil pressure is present but that can create hard start scenarios if the bowls are empty.

    I’m totally on-board with taking advantage of modern updates to improve drivability, reliability and efficiency but in this case, I’d recommend going exclusively with a mechanical fuel pump. If you’re worried about a failure during a road trip might be worth having a spare in the boonie-box. Easy for any minimally competent tech to replace but getting a replacement in a timely manner could be a problem.
    1963 Avanti R1

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    • #3
      Originally posted by EnduroDriver View Post
      Functionally yes but it’s not a very safe option. One of the failure points on a mechanical fuel pump is the diaphragm. When that fails the engine will stop running reasonably quickly due to a lack of fuel supply to the carb. Flipping on an electric fuel pump will probably feed the carb fine but will also push fuel through the torn diaphragm which in turn will fill the crankcase with fuel. Best case it ruins the engine, worst case well that involves the smell of burning fiberglass.

      Going exclusively with an electric fuel pump is probably the most reliable option but has its own safety issues as will. A stuck float needle valve won’t present a safety issue with a mechanical fuel pump as the engine would most likely flood and stop. In that scenario an electric fuel pump could continue to empty the fuel tank until the ignition was turned off. The work around for that is a low oil pressure switch that only allows the pump to start when minimal oil pressure is present but that can create hard start scenarios if the bowls are empty.

      I’m totally on-board with taking advantage of modern updates to improve drivability, reliability and efficiency but in this case, I’d recommend going exclusively with a mechanical fuel pump. If you’re worried about a failure during a road trip might be worth having a spare in the boonie-box. Easy for any minimally competent tech to replace but getting a replacement in a timely manner could be a problem.
      Reading this has me thinking of the horror I would feel if the FP in my R-1 Avanti crapped out on me away from the garage. Yes I do carry a spare, but so what?? You think its a walk in the park to R&R the dam thing? Especially if one is on the highway? That is one nasty job under the best circumstances...having access to a lift is only a marginal benefit. LOL I try to never think of break down scenarios, the reality of those events is far from pleasant.

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      • #4
        I second the..."Not Very Safe !"

        The diaphragm splits open or a valve leaks (two or three) in the mechanical pump, the electric pump will keep on pumping. Guess where a lot of fuel will go...right past the leaking valve or split diaphragm...and into the oil pan..!
        And...that's a safe thing to happen, right ?

        Yes, people have done it over the years, but...

        Mike

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        • #5
          Their is a fuel pump arm seal on the market for a ford pump, might give us peace of mind. Luck Doofus

          Comment


          • #6
            If running a mechanical FP, which I have not done in over 30 years, I'd use the Mopar 318 pump, modified for Stude, and sold by some of our vendors, i.e. Phil Harris. I prefer the Facet, CUBE type electric pump for reliability (only 2 failures since 1985) and versatility (multi-fuel compatible). I prefer the large one (I forget the model but it's in the archives here), which has capacity for a return line. Agree with EnduroDriver NOT a good idea to route the electrical FP through the mechanical FP.

            As for wiring, ideally it would be through through a relay (to avoid excess load on the ignition switch; through the oil pressure sender, as EnduroDriver described in post #2; through an impact sensor switch, and through a tip over switch. It would also include a second electrical circuit with a push button for priming, to avoid excess cranking as described by EnduroDriver. Regretfully, all I have done is wire them direct, with an on/off switch strategically located to avoid theft. Need to get round to wiring them correctly, maybe one of these days.

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            • #7
              I have a three position switch on mine, center is off, up is on, and down is spring loaded (ie, got to hold it down to complete the circuit) to prime the carb after it's been sitting a long time.

              The 'up' position would only be used for a vapor lock situation, or to pump the tank contents into a container, or similar. I agree fully that a sudden failure of the mechanical pump that can be 'overridden' by running the electric is a red flag and should only be used to get the car out of a dangerous situation (over to the side of the road on the interstate, etc).
              Paul
              Winston-Salem, NC
              Visit The Studebaker Skytop Registry website at: www.studebakerskytop.com

              Comment


              • #8
                Originally posted by JoeHall View Post
                If running a mechanical FP, which I have not done in over 30 years, I'd use the Mopar 318 pump, modified for Stude, and sold by some of our vendors, i.e. Phil Harris. I prefer the Facet, CUBE type electric pump for reliability (only 2 failures since 1985) and versatility (multi-fuel compatible). I prefer the large one (I forget the model but it's in the archives here), which has capacity for a return line. Agree with EnduroDriver NOT a good idea to route the electrical FP through the mechanical FP.

                As for wiring, ideally it would be through through a relay (to avoid excess load on the ignition switch; through the oil pressure sender, as EnduroDriver described in post #2; through an impact sensor switch, and through a tip over switch. It would also include a second electrical circuit with a push button for priming, to avoid excess cranking as described by EnduroDriver. Regretfully, all I have done is wire them direct, with an on/off switch strategically located to avoid theft. Need to get round to wiring them correctly, maybe one of these days.
                Ditto on a new pump with modified arm, I happened to purchase mine from Dave Thibeault, but many years ago I did rebuild my original pump with one of the seal kits.

                Comment


                • #9
                  Originally posted by r1lark View Post
                  I have a three position switch on mine, center is off, up is on, and down is spring loaded (ie, got to hold it down to complete the circuit) to prime the carb after it's been sitting a long time.
                  Could you provide more info on this switch and where it can be purchased? Sounds like the ideal solution for a lot of us!

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                  • #10
                    My 62 GT has an electric pump on a switch before the mechanical pump. Not sure why it was installed, but I use it for a quick prime before starting if it sits for a week and then shut it off after start up. I turn on pump, pump gas pedal eight times turn key and it always fires right up. Is this set up OK?

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                    • #11
                      Originally posted by GrumpyOne View Post

                      Could you provide more info on this switch and where it can be purchased? Sounds like the ideal solution for a lot of us!
                      I'll check James, but it's been about 12 years ago that this was purchased so the old mind is a little hazy on where it came from!
                      Paul
                      Winston-Salem, NC
                      Visit The Studebaker Skytop Registry website at: www.studebakerskytop.com

                      Comment


                      • #12
                        Found these on Amazon. There are many out there. Just search 'on-off-momentary' http://www.amazon.com/Momentary-Posi...5821606&sr=8-9

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                        • #13
                          If running both pumps, maybe a spring loaded button (momentary) switch for the electric pump? Push the button for a few seconds, let go and start. No worries about having the pump running if you have an accident or (heaven forbid) rollover. No need to hook up to the oil pressure switch, etc.

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