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Old December 15th, 2009, 04:42 PM
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Default porkchop : Spark color?

Spark color?
Post by porkchop on Sept 17, 2006, 4:32pm

I still can't get my truck to start. It wants to go but just won't light off. I tested the spark and it was orange and sort of weak. All I have ever seen is blue, so what does it mean? Or am I just losing my mind.
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Old December 15th, 2009, 04:42 PM
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Re: Spark color?
Post by luckypabst on Sept 17, 2006, 7:13pm

Could be weak battery or coil but I bet it's voltage drop from running the starter. Most stock wire harnesses have a way to bypass the ballast resistor/resistor wire during startup to increase voltage at the coil and produce a hotter spark.

How did you wire in the ignition circuit?

Chris
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Old December 15th, 2009, 04:42 PM
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Re: Spark color?
Post by porkchop on Sept 17, 2006, 7:44pm

I used a voltage reducer for the coil. The stock coil wire goes to the reducer and then it goes to the coil. Maybe the reducer is to much.
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Old December 15th, 2009, 04:42 PM
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Re: Spark color?
Post by luckypabst on Sept 17, 2006, 8:00pm

You should have a bypass wire, maybe from the starter solenoid or the "start" position of the ign switch that goes directly to the coil + and gives it full 12v only when you're starting the engine.

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Old December 15th, 2009, 04:42 PM
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Re: Spark color?
Post by porkchop on Sept 17, 2006, 8:11pm

I am still running 24v. So I should run a bypass wire? Not really sure I understand that. I know I have a weak spark just need to figure out why.
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Old December 15th, 2009, 04:42 PM
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Re: Spark color?
Post by luckypabst on Sept 17, 2006, 8:25pm

Oh, didn't know that. What's your voltage at the coil with the key on?

Is that resistor designed for 24v? If not, you could have some other problems that may or may not cause the weak spark.
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Old December 15th, 2009, 04:42 PM
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Re: Spark color?
Post by kwai on Sept 17, 2006, 10:26pm

Try running run the coil off of one battery directly. This will eliminate the resistor as a problem until you get it running. The truck I just picked up has a 12 volt coil running off of 1 battery. Does fine.
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Old December 15th, 2009, 04:42 PM
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Re: Spark color?
Post by luckypabst on Sept 17, 2006, 11:16pm

Concerning the coil - what I'd do if it were my truck:

Verify to full certainty that the coil is matched to the resistor. Each coil has a specific internal resistance that needs to be mated to the correct rated resistor to meet a total resistance value. There's more to it than just simply slapping any 'ol coil on there and away you go.

And yes, there are resistorless coils available as well. If your coil is anything close to new, it should have labeled whether it requires a resistor or not. If in doubt, one way to be certain is to purchase a new coil and resistor from the same application - my favorite was mid 60's Ford trucks since I knew they used the coil and resistor style ignition. A decent set should not be terribly expensive and would rule out any mis-match possibilities.

Then, as Kwai said, I'd take power off the first battery for 12 volts to the coil so you don't need any kind of voltage reducer. What sort of voltage reducer are you using? A ceramic resistor has a variable voltage drop, dependant on the amp draw of the ignition system - you'd have to run through an equation to figure the ideal ohm rating for the 15ish volt drop you need.

For the weak spark deal, I'd make certain the battery is fully charged, verify voltage at the coil, both "on" and with the engine cranking and make a routine check of your electrical connections.

Chris
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Old December 15th, 2009, 04:42 PM
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Re: Spark color?
Post by porkchop on Sept 17, 2006, 11:36pm

I have a 3.0 ohm resistorless coil. With the engine cranking the coil voltage is 5.4. The voltage reducer is one I picked up at Napa. I will get the name brand later. I am thinking with the voltage reducer and the 3.0 ohm coil it is dropping the voltage to much. I hate electrical and not very good at it, so this is just a guess.
  #10  
Old December 15th, 2009, 04:43 PM
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Re: Spark color?
Post by brute4c on Sept 18, 2006, 9:23am

Usually the bypass allows for the full voltage of a 12 volt system (I know you are running 24) to go to the coil when cranking and then drops it to 9 or 9.6 volts when running...5.4 in the cranking mode is WAY LOW and does indicate a very weak spark...less than half of what would normally be there in the start mode...

I would pull the resistor and hook to the one battery at least for testing...in the long run, I would run a voltage reducer...24 to 12 volt unit...which I believe you ordered a bit ago...
 

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