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Thread: Hello From Pennsylvania

  1. #1
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    Hello From Pennsylvania

    My Name is Don Millar,

    I am one of the restorers for a Non-profit called Vintage Wings Inc. based out of Franklin, PA.

    We have a 1943 Ford GPW that I have been troubleshooting. I'm looking for information regarding normal operation of the starter in the 6V configuration. the engine starts very slow and I'm trying to find out if this is normal or if there is current loss in the circuit somewhere?

    now that the aircraft restoration is almost done, I have switched to giving the GPW some love. I put in a new battery and starter switch. All wiring, starter commutator and brushes have been re-furbished and cleaned. vehicle has a really hard time starting... any advice would be greatly appreciated as I followed all steps in the manual for troubleshooting this and it's still starting hard.

    Thanks

    Don

  2. #2
    Super Moderator LarrBeard's Avatar
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    [QUOTE=BCB79;15294]My Name is Don Millar,

    We have a 1943 Ford GPW that I have been troubleshooting. I'm looking for information regarding normal operation of the starter in the 6V configuration. the engine starts very slow and I'm trying to find out if this is normal or if there is current loss in the circuit somewhere?

    now that the aircraft restoration is almost done, I have switched to giving the GPW some love. I put in a new battery and starter switch. All wiring, starter commutator and brushes have been re-furbished and cleaned. vehicle has a really hard time starting... any advice would be greatly appreciated as I followed all steps in the manual for troubleshooting this and it's still starting hard.

    /QUOTE]

    From your quick description, it looks like you have done all of the right things. 6-volt starters turn over a lot slower than modern 12-volt starters, but there can still be electrical issues that contribute to slow cranking. It takes a little poking around, but you can find out a lot with a voltmeter, a helper and just a few minutes.

    I'd start at the battery terminals themselves - not the connectors, the actual posts. Look at voltage there, it should be about 6.5 volts. Have your helper crank the beast - battery should stay well above 6-volts. If it drops way down, I'd suspect either battery or a very high current draw.

    If the battery stays up, let's check for voltage drops around the system. Go from the negative post to a good chassis ground. Crank it. You should not have more than a tenth of a volt drop across the negative battery cable, if that much. Check drop from post to the big connector on the battery cable - I've seen some corrosion there - even grease under the connection.

    Let's look at the positive side. Again, check voltage drop from the battery post to the stud on the starter. I'm not a GPW expert. but I think it just has a stud on the starter and the actual connection is internal to the little housing on top of the unit. There should be only a tenth or so voltage drop across the positive cable to the starter.

    Question - are you using really good cables? Cheap auto store cables won't cut it on a 6-volt system, there is just too much current involved with them. The ones in the picture are 0-gauge, many auto store cables can actually be #2AWG.

    Poke about a bit and let us know what you find.
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    Last edited by LarrBeard; 01-22-2021 at 03:20 PM.

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    Thank you Larr, I did take some voltage readings, I will be in the hanger tomorrow to work on the Jeep and will let you know how it goes as well as take some pictures........

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    Super Moderator gmwillys's Avatar
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    Welcome BCB79!

    Good cables make a world of difference, like LarrBeard said. We would definitely love some pictures of all your projects!

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    Super Moderator LarrBeard's Avatar
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    And, don't overlook one of the most obvious possibilities - cold weather and thick oil. The F-134 on the '48 turns over very slowly in this weather, even with BMorgil's VX-1 oil in it. It may literally take almost a second to go from one cylinder to the next on the first engine revolution cycle on a cold morning but a low compression L-134 doesn't have to spin all that fast to wake up.

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    Super Moderator bmorgil's Avatar
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    I had a 55 Volkswagen Bus that was 6 volt. If the cables were the least bit dirty at the connections or, anything that caused the slightest voltage drop it would grind slower than usual. If you have good large diameter wire cable and fresh connections that are tight and clean, and you are sure you have a solid starter, that might be all she's got! I have a 6 volt starter running on 12 volts in mine. I would say the cranking speed is normal for a modern vehicle and quite a bit faster than a 6 volt.

    If all is good and you feel it is still too slow, the bushing in the bell housing that supports the end of the starter could be worn or gone. This will cause a misalignment and a high torque load. In any event the "pro way to go" is with a current test using an inductive amp meter over the battery cable to the starter. The cranking amps should run from around 75 to 150 amps depending on the condition of the motor and a few other things. Anything that adds drag to the rotating assembly. If it gets up over 100 amps I would start looking around for something that is running the current up. Bad brushes in the starter or the bushing's are often culprits. I have seen people use "off the the shelf" battery cables that are aluminum or too small in diameter for 6 volt or the current required. As the voltage drops the current goes up. A 6 volt starter requires larger diameter wire than a 12 volt to produce the same power.

  7. #7
    Super Moderator LarrBeard's Avatar
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    6-volt Starter currents

    Quote Originally Posted by bmorgil View Post
    The cranking amps should run from around 75 to 150 amps depending on the condition of the motor and a few other things. Anything that adds drag to the rotating assembly. If it gets up over 100 amps I would start looking around for something that is running the current up. Bad brushes in the starter or the bushing's are often culprits. I have seen people use "off the the shelf" battery cables that are aluminum or too small in diameter for 6 volt or the current required. As the voltage drops the current goes up. A 6 volt starter requires larger diameter wire than a 12 volt to produce the same power.


    We looked at this putting the '48 back together and did some above and beyond things to reduce the resistances in the starting circuits including adding a braided welding cable jumper from the battery ground at the engine block to the bolt on the flange of the starter. Typical engineer overkill.

    Just to get an idea of how much current we are talking about - a starter with no load on it - tied down to the bench so it doesn't run away - will draw about 70-amps if you apply 5.5 volts to it. (1948 Shop Manual). Oh - By the way #2, the motor's unloaded speed is 4,300 RPM - that's why you tie it down very securely!.

    Here is where it gets interesting - the stall current drawn by that motor. When it goes UHHHHGGH! to turn over that cold engine the first time, if you keep 4-volts on the starter terminal, the motor will draw 400-amps. It takes some real cables to support a 400-amp starting draw! One milliohm of cable, clamp and terminal resistance (one-one thousandth of an ohm) will give almost a half-volt drop!)

    See, we have all kind of information you probably didn't really want to know.....

    By the way, we like airplane pictures as well as Jeep pictures...
    Last edited by LarrBeard; 01-23-2021 at 10:19 AM.

  8. #8
    Super Moderator bmorgil's Avatar
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    Good point Larry. It would be beneficial to watch the voltage also as you crank. When the voltage drops as you crank it the amps go up. If the battery doesn't have the oomph to hold some good voltage it will head on a rapid discharge spiral and grind slowly to death. If it cant hold much over 4 volts it may be very hard to get enough juice to fire the plugs.

    The voltage loss between the starter motor terminal and the battery terminal should not be more than .3 volts and the loss on any ground should not be more than .1 volts per 100 amps. As Larry said if you can stall the starter current will skyrocket. Any resistance will show up.
    Last edited by bmorgil; 01-23-2021 at 06:37 PM.

  9. #9
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    Thank you for the Information and expertise!!

    Our GPW is all sorted out now, the main problem was the starter switch that was purchased from a Rural King. Not enough current was going through the switch and a heavier starter switch was purchased!!

    Also the starter itself was excessively greased when it was sent to have new brushes put in. So as the gentlemen here stated it's always good to check voltage drops through a problem system and see where problems might be.

    Next time I am at the hanger, I will take pictures and post them here for you guys........DC-3(C-53) Included.

    Take care and thank you again.

    Don

  10. #10
    Super Moderator LarrBeard's Avatar
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    One for the Good Guys!

    Quote Originally Posted by BCB79 View Post
    Thank you for the Information and expertise!!

    Our GPW is all sorted out now, the main problem was the starter switch that was purchased from a Rural King. Not enough current was going through the switch and a heavier starter switch was purchased!!

    Also the starter itself was excessively greased when it was sent to have new brushes put in. So as the gentlemen here stated it's always good to check voltage drops through a problem system and see where problems might be.

    Next time I am at the hanger, I will take pictures and post them here for you guys........DC-3(C-53) Included.

    Take care and thank you again.

    Don
    We won on this one! Was the C-53 basically a C-47 airframe with special mods? I don't recognize the critter.

    Ask anytime - but don't take our advice on airframe repairs.

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