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Thread: 6 Volt Electric Fuel Pump Question

  1. #1
    President Member Commander Eddie's Avatar
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    Question 6 Volt Electric Fuel Pump Question

    I have a 6 volt electric fuel pump from Spectra Premium, model SP1124, to install in my '55 President Sedan. My problem is that a previous owner converted this car to 8 volt. I called the company tech support this morning to ask them if this pump could be used with 8 volts with or without a resistor. They seemed a bit flummoxed by this question and I actually had to feed what I thought was the answer to them. I am not real confident in the response I got. So, I bright the question to the experts here. I should mention that this car is currently running on a mechanical pump has has never had an electric pump installed before.
    Will this fuel pump work fine without a resistor, or will it need one? Anyone had experience with this kind of situation?
    Ed
    Ed Sallia
    Dundee, OR

    Sol Lucet Omnibus

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    Commander Eddie, why the change to an 8V battery? Electrical problems with starting? If so, the 8V conversion is just a work around the real problem. I would recommend getting your electrical system up to spec with good functioning starter, generator, regulator, and connections. Bad grounds will cause sub par performance. Plus, the 8V battery is hard on bulbs and other components.Battery cables that are too small will also affect starter performance. I had a prewar Cadillac that had been fitted with an 8V battery instead of fixing the problems. I fixed the problems and installed a new 6V battery and cables, and had a good dependable and functioning electrical system.

    JWL

  3. #3
    President Member Commander Eddie's Avatar
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    Quote Originally Posted by JWL4541 View Post
    Commander Eddie, why the change to an 8V battery? Electrical problems with starting? If so, the 8V conversion is just a work around the real problem. I would recommend getting your electrical system up to spec with good functioning starter, generator, regulator, and connections. Bad grounds will cause sub par performance. Plus, the 8V battery is hard on bulbs and other components.Battery cables that are too small will also affect starter performance. I had a prewar Cadillac that had been fitted with an 8V battery instead of fixing the problems. I fixed the problems and installed a new 6V battery and cables, and had a good dependable and functioning electrical system.

    JWL
    JWL, as I stated, a previous owner did the conversion. I do not know why it was done. It was supposedly done by a professional automotive electrician. I do not have the resources right now to convert it back to 6 volt or upgrade it to 12 volt. The electrical system seems to be working okay with the 8 volt conversion. So, I just need to install an electric fuel pump as a primer pump and backup. I just don't want to install it using 8 volts and burn the thing out. I suppose I could just play it safe and install the resistor.
    Ed Sallia
    Dundee, OR

    Sol Lucet Omnibus

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    President Member TWChamp's Avatar
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    My 1950 came with a new 8 volt battery when I bought the car 3 years ago. As soon as I got the car home I removed the 8 volt and sold it on Craigslist and installed a 10 year old 6 volt battery I had laying under a bush. The car never ran better. All you need to do is install a 6 volt battery and maybe readjust the voltage regulator to a couple less volts.

    If you stay with the 8 volt and want to run the electric pump for only a few seconds as a primer, then you won't need a resistor. If you want to run the pump continuous, then you'd have to figure the amp draw of the electric pump to determine the ohm resistor you need to drop the voltage to 6 volts. You'd most likely do fine with a 1/2 ohm 50 watt resistor.

    You can also buy a 6 volt voltage regulator on ebay for a few dollars that will work for you. It might read something like "regulates 7 to 15 volts down to 6 volts". Just do a search for "6 volt regulator".

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    President Member Commander Eddie's Avatar
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    Quote Originally Posted by TWChamp View Post
    My 1950 came with a new 8 volt battery when I bought the car 3 years ago. As soon as I got the car home I removed the 8 volt and sold it on Craigslist and installed a 10 year old 6 volt battery I had laying under a bush. The car never ran better. All you need to do is install a 6 volt battery and maybe readjust the voltage regulator to a couple less volts.

    If you stay with the 8 volt and want to run the electric pump for only a few seconds as a primer, then you won't need a resistor. If you want to run the pump continuous, then you'd have to figure the amp draw of the electric pump to determine the ohm resistor you need to drop the voltage to 6 volts. You'd most likely do fine with a 1/2 ohm 50 watt resistor.

    You can also buy a 6 volt voltage regulator on ebay for a few dollars that will work for you. It might read something like "regulates 7 to 15 volts down to 6 volts". Just do a search for "6 volt regulator".
    TW - The car has an 8 volt alternator and the voltage regular has been bypassed. Much of the car wiring has been routed through a resistor block. To go back to 6 volts would be a little more involved than you suggest. I might look in to the 6 volt voltage regulator idea. Had not thought of that one. Thanks for the feedback.
    Ed Sallia
    Dundee, OR

    Sol Lucet Omnibus

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    Ed -

    Not a problem, run it, it'll be fine. Even the swapping positive for negative ground...just swap wires if required. (2) extra volts is not going to hurt it..."unless"...it's a cheap pump to begin with...then all bets are off. Quality pump, no problem.
    You can run a 6V starter on 12+ volts as long as you don't grind on it for two minutes, without problem..!

    Mike

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    President Member Commander Eddie's Avatar
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    Quote Originally Posted by Mike Van Veghten View Post
    Ed -

    Not a problem, run it, it'll be fine. Even the swapping positive for negative ground...just swap wires if required. (2) extra volts is not going to hurt it..."unless"...it's a cheap pump to begin with...then all bets are off. Quality pump, no problem.
    You can run a 6V starter on 12+ volts as long as you don't grind on it for two minutes, without problem..!

    Mike
    Mike, Thank you for the feedback. That is kind of what I was originally thinking myself. As a primer pump it should be fine. It is a good quality pump. If my mechanical fuel pump should quit on a trip the electric should still be fine?
    Ed Sallia
    Dundee, OR

    Sol Lucet Omnibus

  8. #8
    President Member RadioRoy's Avatar
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    You could buy a few of these and use them around your car. eBay has lots of these kind of things.

    http://www.ebay.com/itm/DROK-Waterpr...4AAOSwdGFYpU-a

    The only disadvantage is that they put out exactly 6 volts, whereas 6 volts on our cars actually goes from 6.3 volts at rest to around 7 volts running.
    Last edited by RadioRoy; 03-18-2017 at 12:50 PM.
    RadioRoy, specializing in AM/FM conversions with auxiliary inputs for iPod/satellite/CD player. In the old car radio business since 1985.

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