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Joined: Nov 2006
Posts: 173
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My truck had been converted to 12v prior to my taking ownership. I suddenly lost fire to the plugs today, and was wondering if I end up needing to get new points and condenser, is there a difference in 12v verses 6v? I'm hoping that the problem is the coil or wiring but I didn't see anything obvious. As a matter of background, the truck died from about 2000 rpm just like the switch got cut off. I have the O.E. Part numbers for the points and condenser.
Thanks,
Scott


1947, 1950, & 1952 Chevrolet 1/2 ton
1952 GMC 450 series Cab Over Engine
1946 Chevrolet 2 Ton
Joined: Oct 2006
Posts: 9,671
D
'Bolter
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Sounds like you burned out the coil. Did you use a coil with a built ing resistor or instal a ballist resister in the system??
Or it is possible that you just have a broken wire, easy enough to check wire continuity with one of those $3 multimeters.
Jerry should be along here momentarily and explain it to you further.


DG


Denny G
Sandwich, IL
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'Bolter
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Sounds like you burned out the coil. Did you use a coil with a
built ing resistor or instal a ballist resister in the system??

Or it is possible that you just have a broken wire, easy enough
to check wire continuity with one of those $3 multimeters.

Jerry should be along here momentarily and explain it to you further.

DG


Denny G
Sandwich, IL
Joined: Mar 2005
Posts: 1,636
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'Bolter
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First thing I would check is whether or not you have power getting to your coil. Also, recheck the point gap just in case the screw that secures the points to the plate wasn't tight enough and let the points move.

If you didn't lubricate the cam lobes on the distributor where the fiber block meets the cam, it wouldn't take long to wear the fiber down.

The points won't care too much about voltage, but they will burn quicker without the resistor either in the line or built into the coil.

My truck shut down the other day, and it took a little digging to find a wire had come off the back of the amp meter.

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You guys are good- - - -not much need to elaborate any further! I would be sure that there's a voltage-dropping device between the ignition switch and the coil, either a ballast resistor or a nichrome wire. The points will burn pretty quickly without lowered voltage to the coil. With the points closed, a 12 volt ignition system should have about 9 volts applied to the coil (+) terminal. When the points open, the voltage at the coil primary will go back to battery voltage because no current is flowing. To check the integrity of the points, attach a jumper wire to the coil (-) terminal and ground. If the (+) terminal voltage changes from the "points closed" voltage, you've got problems with the points.
Jerry


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I did some checking today in the daylight. I replaced some suspect wires with no effect, still no fire from the coil. I dug around in my junk pile and found a old coil from a piece of farm equipment. Engine spun over twice before firing. So kudos to everyone who guessed burnt coil. I also assumed there was a resistor in line with the coil, there isn't. You know what they say about assumptions. A ballast resistor and new coil is on the shopping list next time I get to town. I have a question about adding a resistor, if I don't provide full 12v at starting, will I have more problems during cranking? Should I add a jumper wire to feed straight 12v during cranking.

Quote
To check the integrity of the points, attach a jumper wire to the coil (-) terminal and ground. If the (+) terminal voltage changes from the "points closed" voltage, you've got problems with the points.

Jerry, would this be done with the points open or closed? I would think that it would be with them open, but my understanding of points ignition is rudimentary at best.
Thanks everyone,
Scott


1947, 1950, & 1952 Chevrolet 1/2 ton
1952 GMC 450 series Cab Over Engine
1946 Chevrolet 2 Ton
Joined: Mar 2005
Posts: 1,636
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'Bolter
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If you install a ballast resistor, then you will want a bypass wire off the starter while the starter in engaged.

As for the points. To test if they are working or not you make sure they are closed and measure the voltage on the + terminal of the coil. Then make a jumper wire and touch it to the - terminal on the coil and touch it to the engine block. If the voltage changes (lowers), then there is a problem in the points.


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Ok, got it, thanks.
Scott


1947, 1950, & 1952 Chevrolet 1/2 ton
1952 GMC 450 series Cab Over Engine
1946 Chevrolet 2 Ton

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