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Old 12-20-2019, 04:37 PM   #1
Karl
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Default No Go -Coil Voltage

Having parked by stock 1934 in the garage 3 weeks ago I went to start it up today and No go -the motor spins but no fire .. The only thing I have done is fit some LED taillights and had the ignition on to check flasher was working, My first thought was, even though I was careful , that I left it on to long and burnt the coil out , However before I pull the coil I checked voltage at the coil . With a fully charged battery and obviously a cold resistor I'm getting 2.9 volts which I think is low . I have has some intermittent missing when hot which I have been chasing and thought I had fixed. Before I pull the coil should it run with 2.9 volts at the coil? Could this fit with a faulty resistor ?
Some advice for this electrically challanged guy would be appreciated -Karl
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Old 12-20-2019, 04:43 PM   #2
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Default Re: No Go -Coil Voltage

I don't think 2.9 volts at the coil will produce a spark. run a jumper from the hot side of the floor starter switch to the coil and see if it starts. You could have bad connections somewhere if the battery is indeed good and fully charged. What is your fully charged voltage at the battery?
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Old 12-20-2019, 05:47 PM   #3
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Default Re: No Go -Coil Voltage

Test the battery voltage first. Test the voltage on both sides of the ignition switch. Ignition switches are a problem area especially if they are old original units. Ignition resistors don't give much trouble unless they are non genuine Ford ones, but there seems to be a fixation about them on the Barn. Change the condenser, they give much more trouble than coils do. What condenser are you using ? Did you actually sight how good the spark is at the plugs. 2.9 volts at the coil ( tested with dist points open or closed ? ) could be Ok for starting. The longer you have the ignition turned on while trying to start (cranking) then the hotter the resistor will become and therefore a lower voltage at the coil will be the result What about fuel, too much or not enough when starting. Test, Test, Test and not just guess what is happening. Regards, Kevin.
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Old 12-20-2019, 06:16 PM   #4
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Default Re: No Go -Coil Voltage

Thanks 6.3 Volts at Battery 6.3 Volts into and out of ignition switch 6.3 Volts at ignition side of resistor and 2.9 volts at coil side of resistor and at coil . I suspect the resistor is the problem and will jump it to confirm this afternoon I have a FORD NOS in my spares So may just replace it. Condensor relatively new but I have a Vertex Magneto condensor that will go in if I do end up changing the coli -Karl
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Old 12-20-2019, 07:47 PM   #5
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Default Re: No Go -Coil Voltage

Karl, as I said before the voltage out of the resistor at 2.9 volts does not mean that the resistor is faulty. If the ignition has been on for a couple of minutes or the resistor is warm from previous testing (engine not running) then you will get a voltage reading like that. The hotter the resistor gets the higher its resistance value and the lower the output voltage will be. The resistor is designed to operate with the engine running and not just sitting with the ignition "" ÖN " and the engine not running. All voltage testing has to be done with the distributer timing points closed so that the ignition coil is drawing current, otherwise its a waste of time. Check the spark strength at the plugs. DONT keep blaming the resistor because it is more than likely OK. I have worked on these cars for over 50 years and have rarely found a faulty resistor. The resistors that play up are the reproduction ones. Original FORD ones are the only ones to use. Regards, Kevin.
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Old 12-21-2019, 01:25 AM   #6
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Default Re: No Go -Coil Voltage

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Koates is right-on. Your 2.9 volt input to coil is good. We will never see more than 3.0 volts at the coil with engine stopped. (with engine running, points opening and closing, averaged voltage reading there will then jump up to 3.5 or more) Nothing wrong with your ignition resistor, switch, or the rest of the circuit providing input to the coil. Problem is elsewhere.

Koates is also correct in that the ignition resistors are rarely known to fail. Coils are known to be fragile, condensers fail including brand new ones, ignition switches get dirty and create a voltage drop, but the resistors are very robust, most original resistors still function just as designed.
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Old 12-21-2019, 01:37 AM   #7
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Default Re: No Go -Coil Voltage

Not to say a resistor is bad. you're checking that with a jumper. Most likely your condenser is problematic. But who knows!
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Old 12-21-2019, 02:52 PM   #8
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Default Re: No Go -Coil Voltage

Quote:
Originally Posted by JayChicago View Post
Koates is right-on. Your 2.9 volt input to coil is good. We will never see more than 3.0 volts at the coil with engine stopped. (with engine running, points opening and closing, averaged voltage reading there will then jump up to 3.5 or more) Nothing wrong with your ignition resistor, switch, or the rest of the circuit providing input to the coil. Problem is elsewhere.

Koates is also correct in that the ignition resistors are rarely known to fail. Coils are known to be fragile, condensers fail including brand new ones, ignition switch get dirty and create a voltage drop, but the resistors are very robust, most original resistors still function just as designed.
You are right

I re-looked at things last night prior to replacing the resistor and sure enough ignition is fine ie when it was darker there was definitely spark visable at the plug. I also realized with my head under the hood that with all my wifes cranking there was no smell of gas. Sure enough no gas flow from the pump to the carb . I found a small crack in the (brand new ) plastic fuel filter I recently placed in the fuel line before the pump and this was sucking air. Replaced the fuel line and the car started right up

I always say that 90% of fuel problems are electrical but this was a fuel issue !
Thanks everyone - As per usual I learnt a lot from you all today

Karl
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Old 12-21-2019, 03:00 PM   #9
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Default Re: No Go -Coil Voltage

Good to hear! Thanks for posting the follow-up so the rest of us can learn from what you experienced.
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Old 12-21-2019, 06:07 PM   #10
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Default Re: No Go -Coil Voltage

^^^^^^ +1
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Old 12-21-2019, 06:17 PM   #11
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Default Re: No Go -Coil Voltage

Good catch Karl. So you see whenever its an electrical fault then its always fuel. Merry Christmas to you and yours. Regards, Kevin.
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Old 12-21-2019, 06:45 PM   #12
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Cool Re: No Go -Coil Voltage

Quote:
Originally Posted by koates View Post
So you see whenever its an electrical fault then its always fuel.

or 'smoke'...
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Old 12-21-2019, 10:21 PM   #13
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Default Re: No Go -Coil Voltage

I also appreciate the followup. nice to see it's working for you!


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