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Thread: Jump start 6-volt car with 12 volt battery

  1. #1
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    Jump start 6-volt car with 12 volt battery

    You guys always have the right answers, here's a good question for you.

    Can I use a 12 volt battery to jump start (via jumper cables) a 6 volt car. Or, am I looking to burn something up. I used to do it on an old (1959) volkswagen I drove in high school, and always wondered what would break. It may take some work to get the 1940 model 51 to run after 20 years of storage. I'll be giving it the greatest chance to start on the first try (new plugs and ignition parts, rebuilt carb, rebuilt fuel pump, clean fuel lines and tank) but that 6 volt will only crank so long without recharging. And, I'll want to crank it for a while without starting to get the new oil worked thru-out the bearings and verify some kind of oil pressure.

  2. #2
    Senior Member imported_Guffin's Avatar
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    Re: Jump start 6-volt car with 12 volt battery

    Some restorers convert to 12 V but leave the 6 V starter. If there is enough resistance in the wire it may not hurt the starter. However, if you temporary connect 12 V to a 6 V system you may burn all 6 V lamps that happen to be on. Also, I don't think a 12 V battery will crank the engine loner time, only faster. Why not prime the cylinders with oil and crank it by hand? If the engine has a full flow oil cleaner you could unscrew the connection and force oil into the oil channels. There may also be some plugs into the oil channels which you could screw out and press in oil. I am not so familiar with the -40 Buick engines even if I recently bought a Buick -40 model 56S, but I have not got it home yet.

    Jan
    Buick 32-87
    Buick 40-56S
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  3. #3
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    Re: Jump start 6-volt car with 12 volt battery

    I have done it many times. Just make sure all the lights and radio are off.
    37 46 modified with 455 & all the toys
    40 56C original restored (driven over 100,000 miles by me
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    Re: Jump start 6-volt car with 12 volt battery

    Guffin, thanks for the info. I will do all of the regular stuff prior to trying to start the car( remove spark plugs, oil in the cylinders, hand turn to break things free, then replace plugs to start). But if it does not start easily it may run the battery down before I get it running and would like to use the 12 volt battery as a back-up rather than waiting 2-3 hours for a quick charge on the 6 volt battery. Also, I do have an external oil cleaner/filter and like your idea of pumping oil into the oil circuit. What devise do you recommend to do the pumping. I guess I could use a hand pump one would use to put gear oil into the differential (fit the plastic hose over the supply fitting running from the oil filter. Your thoughts??

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    Re: Jump start 6-volt car with 12 volt battery

    Thanks Joe, I'll verify all lights are off as well as the radio. Should I disconnect the generator?

  6. #6

    Re: Jump start 6-volt car with 12 volt battery

    I have jumped 6V cars many times with 12 V. I agree with turning off all the lights, radio and accessories. In addition, though, I pull off one lead from the 6V battery terminal and connect the jumper to the free lead. This eliminates the danger of battery explosion when current surges into the 6V battery.

    Once the jumper is connected, turn on the ignition and quickly crank the car until it starts. Do not delay or the 12 V could damage the instruments. As soon as the engine starts, disconnect the jumper and jam the lead back onto the 6V battery terminal. If you're lucky, the engine will keep running through this transition (keep the revs up so it will run on the generator during brief time the battery lead is not connected) and you'll be on your way.

    Good luck!

    Bill.

  7. #7
    Senior Member imported_Guffin's Avatar
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    Re: Jump start 6-volt car with 12 volt battery

    You can try a hand pump. If you have compresses air you can put oil in a hose connected to the oil filter and attach compressed air to the other end.
    If breaker points, spark plugs, carburetor and gas pump are ok the car should start easily. Pay special attention to that gas has been pumped and filled the carburetor and that the breaker point are clean and free from oxside.
    Good luck!
    Buick 32-87
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    Re: Jump start 6-volt car with 12 volt battery

    To prime the oiling system, remove the distributor after carefully marking its location relative to the cylinder block and the location of the rotor relative to the distributor body. With a flashlight, make an accurate note of the direction of the slot in the oil pump drive shaft because it will have to be there when you reinstall the distibutor. Then, insert a large screwdriver into the slot on the oil pump drive shaft and turn the shaft by hand until you feel resistance building. Continue to turn the oil pump drive shaft probably another ten to twenty revolutions. This will be enough to get oil to the cam, main and connecting rod bearings. I don't right now remember which direction you turn the shaft. You have an oil filter so disconnect the oil filter inlet pipe and turn the pump shaft one way and then the other until oil flows out of the pipe. This tells you what direction to turn the shaft. Then, reconnect the oil line and keep cranking until you have the engine pumped up. Some people will use an electric drill to build pressure but I've never found it necessary. Just remember that the more blisters you get, the more oil has been moved into the critical parts. Once you have the oil system primed, replace the distributor being careful to align the marks you made before you removed it.
    Charles Grier
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  9. #9
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    Re: Jump start 6-volt car with 12 volt battery

    Since you are putting in new plugs, I would just remove all the plugs and then crank the engine over till you see the slightest movement in the oil pressure guage. Then recharge the battery while installing the rest of the new parts.

    Also I'd make sure there was gas in the carb. I'd do this by disconnecting the fuel supply line in a convenient place and hooking up a temporary hose to the line, through which you could introduce gas into the carb.

    By the time you have this done, the battery will be sufficiently charged to crank the engine over for starting. There are lots of older 6 volt cars out there running well yet, so don't discount that battery you have till you know it is no good.

    JD
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  10. #10
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    Re: Jump start 6-volt car with 12 volt battery

    You should disconect the generator while doing this, also you can burn your 6v ignition coil out. when I start an old 6V system with a 12V what I usaully do is disconnect the accessories and the generator and temporarily install a 12V coil or a proper ballast resistor in the power wire for the coil to reduce volts to 6v at coil, and use the 12v battery directly with the starter without going through the six volt at all. While I have done the 12v jump to 6v, don't forget you can get a battery explosion. Also on priming priming the engine by the screw driver method, be sure the oil pump is not driven directly from the camshaft, unlike more modern engines which utilize the distributor gear to drive the pump most older engines drove through a Non removable (without major engine disassembly) gear off the cam. so when you try to turn the pump you would think it is siezed. Best method is to force oil into the oil galleries if your pump has the "direct" gear drive.
    Scott T.
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