Cranks but No Spark Fury

[Clover]

Obviously it is below spec, so technically, it’s bad. But it is not likely to be the reason your car doesn’t start.

 

[Clover]

I wouldn’t bother replacing the coil if I were you.

 

[Clover]

You said that you had spark from the coil but no spark from the plugs. Spark from the coil is definitive. No spark at the spark plugs is not definitive.

 

[Clover]

I believe that you have erred in your spark-at-plug test and when you get some help you will find that you do have spark at the plugs. Then you can stop going down the garden path and address your fuel problem. Just my guess.

 

[Clover]

If it is truly a situation of spark from coil, but no spark at the plugs, here is the great news: it must be the cap and/or rotor and/or ignition wires. There is absolutely no other possibility!

 

[Clover]

All this assumes that it isn’t just your severely-carboned plugs. Check for spark to the plug, as opppsed to through the plug. And get new plugs for sure!

 

[Turboomni]

Have you tried starter fluid down the carb yet and see if it fires???

 

[Turboomni]

Also does anyone know how well a 12 volt coil works with only 6 volts? Is the spark powerful enough to bridge the gap between the rotor and cap?

 

[Clover]

A 12v coil will have a weak spark in a 6v system.

 

[Turboomni]

Yes I agree it will. I did a bit of digging into this and it is worse than you may think running a 12 volt coil on 6 volts. Here is an excerpt.

"""Now: You ask about a 12 volt coil working on 6 volts. I know this is math and most people don't like math but since you're developing a magnetic field within a coil using six volts, when that field breaks down (which is what breaker points do) you should get a spark. That coil is designed to work on 6 volts and its output should be around 12,000 volts. But if you use a 12 volt coil that may be designed to give you a 12,000 volt spark, powering it with only 6 volts will NOT give you half the power (AKA 6,000 volts) but you'll get 1/4th the spark power. In other words, 3,000 volts. WHY? Because of the inverse square law, which states that energy applied over an area will be four times weaker at half the voltage. """

 

[Turboomni]

With that,, fuel problem or not this should also be addressed.

 

[Big_John]

Yes I agree it will. I did a bit of digging into this and it is worse than you may think running a 12 volt coil on 6 volts. Here is an excerpt.

"""Now: You ask about a 12 volt coil working on 6 volts. I know this is math and most people don't like math but since you're developing a magnetic field within a coil using six volts, when that field breaks down (which is what breaker points do) you should get a spark. That coil is designed to work on 6 volts and its output should be around 12,000 volts. But if you use a 12 volt coil that may be designed to give you a 12,000 volt spark, powering it with only 6 volts will NOT give you half the power (AKA 6,000 volts) but you'll get 1/4th the spark power. In other words, 3,000 volts. WHY? Because of the inverse square law, which states that energy applied over an area will be four times weaker at half the voltage. """

Excuse me, but what does this have to do with anything here?

This is a 12 volt car with an original coil. Why confuse matters?

 

[Clover]

The issue is also complicated by the ballast resistor. The coil only receives full voltage during cranking. Otherwise the ballast resistor is key.

 

[Big_John]

To the OP, as has been said a couple times, the plugs look carboned up. Toss a new set of plugs in and give it a try.

 

[Turboomni]

Maybe I am totally confused. This is a points car with a Ballast resistor that has a 12 volt battery correct? If so the coil should be a 6 volt coil not 12 is all I am saying . If it is a electronic ignition system then I am off base and my apologies as I don't have any experience with this.

 

[65sporty]

Maybe I am totally confused. This is a points car with a Ballast resistor that has a 12 volt battery correct?

12v coil even though when running through the ballast resistor it knocks it down to about 8.5-9.5v

 

[Big_John]

Maybe I am totally confused. This is a points car with a Ballast resistor that has a 12 volt battery correct?

Yep... The ballast resistor does not come into play to limit CURRENT until the car has started. The car doesn't start... therefore the ignition switch returning to "run" so that the CURRENT to the ignition coil etc. isn't limited.

 

[Great Pumpkin]

I did clean the plugs yesterday, same results, wont start. will review all on Saturday.Thanks for your posts!

 

[Turboomni]

Ahh yes I see and stand corrected. So when cranking a 6 volt coil gets 12 volts till it starts. Sorry guys. It makes sense

 

[65sporty]

If you had spark at the coil, check the coil wire, dist cap and rotor.