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Thread: Engine Will Not Turn Off

  1. #1
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    Engine Will Not Turn Off

    My 1949 2R5 truck, champion engine, converted to 12V in the early 1980's, universal keyed ignition switch installed at the same time, developed this last week the habit of not turning off by turning the key off, not all of the time, but most of the time. I turn it off now with the clutch then pull the coil wire to ensure that the ignition is off. I made the guess of buying a new switch, but that is not the problem. It does the same with the new switch. There is a red light on the universal turn signal switch that stays on when the ignition is on. That light turns off when I turn the ignition off, so it does seem like the circuit is deactivated, but somehow power still goes to the distributor.

    Does anyone have an idea of what may cause this? Thanks.

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    Does it have an alternator? If so, what kind?

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    President Member bensherb's Avatar
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    Yes, depending on how the alternator is wired it can "feed back" and power the ignition even with the key switched off.

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    You probably have a Delco alternator and it is self energizing. I have the same situation with two of mine so I put in a switch so I can deenergize the alternator.
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    Thank you all. The alternator is from a 1965 Ford truck. I made this conversion long before there was an internet or forum. A friend had a scrap Ford truck, so I took the parts from it (alternator, regulator, wiring harness,) made a bracket, and it worked fine until this came up. I wired it the same as it was wired on the Ford truck.

    When I turn it off with the clutch I have been pulling the coil lead to ensure no power is going to the points. If it is the alternator feeding it, then it seems that will stop happening when I stop the engine from turning with the clutch. I take this to mean that I will not have to add the switch. What do you think?

    I will return the old universal ignition switch to use. The new one looks the exactly the same as the old one, but the key went from a brass one with a nice pattern to a shiny metal one that looks like something that is part of a small child's toy - way too cheap looking.

    Again, thanks for your help.

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    Turn it off with the clutch??

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    The cure is to put a diode in the charge signal wire. It can be feeding back and energizing the ignition. It is very common with a GM unit. I guess it could be possible with a Ford unit.
    james r pepper

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    Thanks for your further advice. I can look at that. I am not up on my electronic knowledge, but I believe I remember a diode being like a check valve, allowing one way only flow.

    Clutch turn off is engage 3rd gear, step on brake, let clutch out.

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    President Member Xcalibur's Avatar
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    Ron Hall's B;ville Avanti did the same thing the first time it was started with the racing engine... on the Salt Flats! Needed to put a tail-light bulb in the system (don't recall where; it was 1988) to add enough resistance so it would shut off.

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    President Member bensherb's Avatar
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    Do you have an idiot light, in the charging system? It is what takes care of that problem in a stock system. One side of the bulb will go to power + and the other side will go to the F treminal on the Alt. That field terminal is ground when the Alt is stopped so the light comes on. Once the Alt starts making power the F terminal changes to + and the light goes out. With both sides of the circuit being the same ,(+), the field stops being excieted and the Alt stops making power when the engine stops until it's excieted again. Come to think of it , if you're using the stock ford regulator, it could have a shorted field coil and cause the problem depending on how its wired. I usually use a GM internal regulator type alternator, they're much easier to work with.

    Of course the easy way to assure the alternator won't be a problem like this, is to install a GM type, 1 wire alt. That wire goes to the + side of the battery and you're done, it doesn't involve anything that could affect the ignition. The GM 3 wire one will work too, just get the stock terminal plug, the larger of the two wires goes to the batt terminal, same one that goes to the battery, and the small wire goes to one side of the idiot light the other side of the idiot light goes to power; that batt terminal will work for that too if you want to leave the light at the Alt. The light can be replaced with a resistor if you want, I can't remember the value for sure off hand, but 5 ohm 10 watt comes to mind.

    My GT currently has a Chrysler alt and and regulator, it came to me that way and is working fine, but it will be replaced with the GM if either goes bad.

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    Thanks for your advice. The truck has its original amp gage. Except for this new thing that I can get around because of having my alternate engine stop, the charging seems to work fine. I will certainly consider changing to the one wire type if something needs to be replaced.

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    It seems strange that after working fine for over 30 years you would have to add a diode to the charging circuit. I would do a bit more testing. First I would disconnect the wire coming from the generator armature at the armature terminal of the voltage regulator, then start the engine and see what happens when you try to turn it off. If it keeps running then the current that is supplying the ignition is not coming from the generator. (Use normal precautions when disconnecting the wire and positioning it so not to touch ground.)

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    Could the solenoid be stuck and be feeding thru the 12v bi-pass? Just a thought. -Jim

  14. #14
    President Member Corley's Avatar
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    Since you have a universal key switch, you could just connect the ignition wire to the coil to the Aux connection on the switch, assuming this is hot when in the start position. If not hot during cranking, then connect everything else on the car to the Aux connection, and only the coil to the Ign position on the switch. You want to make sure the coil is not connected to any ckt that the alternator is connected to when the switch is in the off position.

    By the way, pulling the high tension wire from the coil won't ensure the points are not getting power, it will only prevent spark from reaching the distributor. I hope you actually meant that you were pulling one of the small primary wires from the coil.
    Corley

  15. #15
    President Member Jerry Forrester's Avatar
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    Quote Originally Posted by Robert Crandall View Post
    My 1949 2R5 truck, champion engine, converted to 12V in the early 1980's, universal keyed ignition switch installed at the same time, developed this last week the habit of not turning off by turning the key off, not all of the time, but most of the time. I turn it off now with the clutch then pull the coil wire to ensure that the ignition is off. I made the guess of buying a new switch, but that is not the problem. It does the same with the new switch. There is a red light on the universal turn signal switch that stays on when the ignition is on. That light turns off when I turn the ignition off, so it does seem like the circuit is deactivated, but somehow power still goes to the distributor.

    Does anyone have an idea of what may cause this? Thanks.
    Robert, do you have an electric fan on your radiator?
    Jerry Forrester
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    Wow! Lots of further advice. Many thanks! It will be a while before I can walk through all of them. I will try easier ones before trying the #12 suggestion. #13 is a very easy check. I will disconnect the 12v bypass before I start it again. I ran that wire after recently learning from the forum why that 'I' terminal is there. That terminal sat unused for more than 30 years. I use the clutch pedal switch to activate a Ford solenoid, so, for the suggestion in #14, I can move wires around because I do not use the start position. Also from #14, I learn more. I now know that pulling the coil wire does not prevent current from going to the points. Thanks. For #15 - I do not have an electric fan.

    If the alternator is providing current, then it should stop when I stop the engine with the clutch. I believe I should be able to confirm no further charge being fed to the distributor by using a test light or meter. I will look at that also.

  17. #17
    President Member bensherb's Avatar
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    Quote Originally Posted by Jerry Forrester View Post
    Robert, do you have an electric fan on your radiator?
    Even though he does not have an electric fan; good catch Jerry, I'd forgotten about that one. I bet everybody who has used an electric fan without a relay has run into that at some point.

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    Turn it off with the clutch?????

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    President Member TWChamp's Avatar
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    Quote Originally Posted by tim333 View Post
    Turn it off with the clutch?????
    Pop the clutch to kill the engine, although this isn't a good way to stop the engine, except in an emergency.

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    Disregard #12 suggestion , I thought you had a generator and a regulator with screw terminals.

  21. #21
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    Here is an update. I disconnected the wire from the 'I' terminal on the Ford starter solenoid, and the engine stopped when I turned it off, every time. I then reconnected the wire, and the engine still turns off, every time. I returned my 1980's universal ignition switch because I was overly bothered by the tinkertoy key that came with the new one. So, the problem went away before I could trace it down. I now have a nut driver in the truck, so I can remove the wire from the ignition terminal while the engine is running, if it ever does it again.

    Again, thanks for all of the suggestions.

    Unrelated note: While driving the truck last night a man driving next to it asked if I would stop and take a photo of him standing next to the tail gate. His name is Studebaker, and he showed me his drivers license to prove it. That was fun.

  22. #22
    President Member TWChamp's Avatar
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    I've taken GM solenoids apart to fix that same problem. The trouble is when it happens, you don't know it messed up until you try to shut it down, and while it's making contact, it's also sending too much voltage to the coil. This could overheat the coil and burn it out.

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