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Technical Electric fuel pump safety switch controlled by tach signal-who’s done it?

Discussion in 'The Hokey Ass Message Board' started by 57ChebbieTrk, Jul 22, 2020.

  1. 57ChebbieTrk
    Joined: Dec 31, 2012
    Posts: 18

    57ChebbieTrk
    Member

    Update: I have it wired in and plumbed. The pump primes for three seconds, just as it should, then I crank it and motor fires, but I am only getting 3-4 psi fuel pressure, no matter where I set the regulator.
    The motor won’t stay running unless I pump the throttle, and it acts as though it starving for fuel.
    I’m going to add a pressure guage right at the output of the pump, back at the tank to see where the pressure loss is occurring.
    This damn thing is driving me nuts. IMG_3108.JPG


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  2. squirrel
    Joined: Sep 23, 2004
    Posts: 55,942

    squirrel
    Member

    What kind of pump is it?
     
  3. 57ChebbieTrk
    Joined: Dec 31, 2012
    Posts: 18

    57ChebbieTrk
    Member

    Carter PN P4600HP Adjustments.JPG


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  4. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 5,217

    2OLD2FAST
    Member
    from illinois

    Diode between terminals ??
     
  5. SCTA requires these, all new cars have them. You can find them as low as $10 https://www.pegasusautoracing.com/p...ource=google&utm_medium=cpc&utm_campaign=1108
     
  6. 5brown1
    Joined: Apr 13, 2008
    Posts: 234

    5brown1
    Member

    I installed it last week and love it. If I left the car sit for two weeks I would have to crank it over for a long time
    before it would start when using the pressure safety switch. I now turn the key on and get 3 seconds of prime, turn it off and on and get another 3 seconds and it starts right up. Much easier on the starter.
     
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  7. 57ChebbieTrk
    Joined: Dec 31, 2012
    Posts: 18

    57ChebbieTrk
    Member

    As per instructions.. Not sure why, but the instructions say that the pump may toggle on and off without it.


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  8. H380
    Joined: Sep 20, 2015
    Posts: 483

    H380
    Member
    from Louisiana

    This is what we use. Very easy. Very reliable. Set the switch point on the blue pot.
    71h8IRx8epL._AC_SL1000_.jpg
     
  9. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 5,217

    2OLD2FAST
    Member
    from illinois

    Reason I asked is I looked at the online wiring instruction & saw no mention of it ..
     
  10. G-son
    Joined: Dec 19, 2012
    Posts: 1,277

    G-son
    Member
    from Sweden

    Electric motors, as well as anything else built of electromagnets (such as ignition coils) can put out a real mean electric pulse when the electricity running through it is switched off. On an ignition coil you can see it as a spark on the points, when the condenser is bad/not installed, we're talking many hundred volts in 12V systems.

    That pulse is a problem, it can burn ignition points and other types of switches/relays eventually, and if it's electronically switched one single pulse can burn the electronics or disrupt the control system. A small, cheap diode installed in the correct place kills the pulse by letting it bleed off harmlessly, and everything survives much longer.
     
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  11. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 5,217

    2OLD2FAST
    Member
    from illinois

    G-son thank you , great understandable explanation , very much appreciated !
     
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  12. 57JoeFoMoPar
    Joined: Sep 14, 2004
    Posts: 6,138

    57JoeFoMoPar
    Member

    I understand the premise of these switches, but IMHO it defeats one of the best features of having an electric pump, that being that you can bring full fuel pressure up with a filled carb to an engine that has sat, greatly easing cold starts. Sometimes you want the pump to run for whatever reason.

    I just have a basic on/off toggle for my key-hot fuel pump installed in between my water temp and oil pressure gauge on my 3 gauge set. A basic $2 part from any hardware store. Works perfectly.
     
  13. H380
    Joined: Sep 20, 2015
    Posts: 483

    H380
    Member
    from Louisiana

    That Murphy speed switch I posted does the same thing as your toggle switch. It sits parallel to the oil pressure switch. It powers the fuel pump when you have oil pressure below the pressure switch activation. When you have enough RPMs the speed switch opens up. By then you have enough oil pressure and the pressure switch controls the fuel pump.
     
  14. 57ChebbieTrk
    Joined: Dec 31, 2012
    Posts: 18

    57ChebbieTrk
    Member

    Update to the update: It is running! I believe since all the fuel lines got replaced, I had to get all the air out of the system, and get fuel flowing continuously to the carb.
    Set the fuel pressure to 5 lbs. The Edelbrock seems to like it.
    My only issue now is the pissed off old neighbor lady down the street. I just ripped past her house and she was not amused.


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