No spark

[Skolfield]

I have a 1953 buick special that won't spark. New points and condenser. New sparkplugs. No spark from coil. Coil is getting electricity. Any ideas?

[Bloo]

Check voltage from the points wire to ground with the points closed, and with the points open. You don't need to know the exact voltage. A test light will work.

 

You should have battery voltage (light on) with the points open and no voltage (light off) with the points closed. Let us know what you find.

[Oldtech]

if no spark from coil and you have power to it, suspect breaker points. As Bloo says, testing the point side will soon tell you if they are doing anything.

If points are good and working. as in adjusted properly and no wires grounded that shouldn't be,  I would put the old condenser back in and try it.

If still nothing  it COULD be the coil has died. 

[EmTee]

If you have an Ohm meter, an easy check would be to remove the primary wires and verify no continuity between the "+" and "-" terminals and the coil's case.

[Skolfield]

Tried what Bloo said. Test light still on with points closed. ?

[JFranklin]

2 hours ago, Skolfield said:

Tried what Bloo said. Test light still on with points closed. ?

Dirty contacts? even if new maybe.

Edited October 9, 2021 by JFranklin (see edit history)

[JohnD1956]

What did you gap the new points to?  Might be .017 if like the '56.  

[Bloo]

Yes, the points should ground that wire and turn the light off when they are closed. Try dragging a little strip of paper soaked in brake cleaner or rubbing alcohol between the contacts to get any crud or grease off.

 

Also, the breaker plate (which the points bolt to) has to be grounded solidly. It moves when the vacuum advance works. The ground is usually a special piece of high-flexibility wire. from the breaker plate over to the distributor case. Make sure it's there and not broken.

 

If the engine is freshly painted, make sure that paint is not preventing the distributor case from grounding to the block.

 

 

Edited October 9, 2021 by Bloo (see edit history)

[Skolfield]

Got it working. Thanks for the advice.

[Ronnie]

1 hour ago, Skolfield said:

Got it working. Thanks for the advice.

 

If you describe what you did to get it working it might help others with the same problem in the future.

[ghaskett]

Check the resistor to the coil. If it's 65 some odd years old, it's a cheap replacement anyway.

[Frank DuVal]

1953 Specials were still 6 volt systems. I have never seen an ignition resistor in a 6 volt coil circuit.🤔

[Grimy]

13 minutes ago, Frank DuVal said:

I have never seen an ignition resistor in a 6 volt coil circuit.

Then you have never seen the ignition system on a Pierce-Arrow through 1928.  Sorry, don't have a photo to share.

[Frank DuVal]

Caught me, I have not seen one close enough to study. Almost bought an early 30s back in the late 70s.

[Bloo]

Some 30s Fords also have an ignition resistor. Also old Buicks with the "mailbox" coil (teens? 20s?). Some Dodge Brothers too. Maybe others.

 

Two things I have NOT seen however, and would like to be proven wrong about:

 

1) A 6 volt coil of the round form factor we all know today that is made to be used with a resistor.

 

2) A 6 volt car with a "starting bypass" that shorts out the resistor, as commonly seen on 12 volt cars.

 

Back on topic, I'm pretty sure there is no resistor or resistor wire in the 53 Buick this thread ia about.

[EmTee]

15 hours ago, Bloo said:

1) A 6 volt coil of the round form factor we all know today that is made to be used with a resistor

 

I have a 1964 MOTOR Manual that has a nice general ignition theory of operation discussion which goes into detail about ignition coils; specifically 6V vs. 12V.  It states that there's a series resistor built into the 12V coils, which is absent from 6V coils.  It goes on to say that's why a 12V coil can't be used on a 6V system.  I suppose using a 6V coil on a 12V system is possible if an appropriate external resistor is wired in series with the IGN side of the coil (and isn't bypassed during cranking).

 

Based on the above, I presume there's no need for a cranking 'bypass' on 6V systems as it simply runs on 6V all of the time.  Constant 12V operation, however, would cause quick erosion on breaker points.  It was my understanding that 12V systems generally ran with about 9V at the coil (using ballast resistor or resistance in primary feed wire).  I'm speculating that the internal resistor in a 12V coil then reduces the voltage at the breaker points to ~6V.  That would provide a somewhat 'hotter' spark than a 6V system, but maintains similar breaker point longevity.

 

Comments?

[JohnD1956]

My understanding is the 12 volt system uses the ballast resistor to reduce the coil to 6 volts after the car is started. Thus a 6 volt coil on a 12 volt system may result in hard starting?  

[Bloo]

I think MOTOR might have that a little wrong.

 

Coils for 6v cars have a primary resistance of about 1.4-1.5 ohms.

Coils for 12v cars with no ballast resistor (and no resistance wire) have a primary resistance of about 2.8-3.0 ohms.

Coils for 12v cars with a resistor (or resistance wire) have a primary resistance of about 1.4-1.5 ohms, and a are used with a series resistor to make up the rest of the 3 ohms.

 

There is more to the story of what goes on inside a coil, but I imagine the current drawn with the points closed and the engine off is all about the same.

 

On a 12v car with a resistor, the coil is running on about half of the available 13.8-14.7 system voltage. The coil sees  maybe 7 volts or a little more with the engine running and the charging system working. That's about the same as the voltage a coil on a 6 volt car sees with the engine running and the charging system working.

 

When you are cranking the engine, the voltage available will be much less. On a 12 volt car, the cranking voltage might pull as low as 10 volts or maybe even lower before the battery is no longer able to crank. The ignition now has to run on significantly less voltage than it is designed for, maybe 5.25 volts instead of 7 on a car with a resistor (or resistor wire). It only gets worse when the engine chugs down while cranking. Right when you need the spark to be hot, it is at it's absolute weakest. A similar situation exists on 6 volt cars.

 

With a starting bypass, full battery voltage is sent to the coil while cranking. The 12v ignition coil, designed to run on about 7 volts with the resistor, might get 9-11 volts. You get a hotter than normal spark while cranking. This makes the car much more likely to start when the battery is low. It is the biggest real world advantage of a 12 volt system over a 6 volt one. I have not yet seen a 12 volt conversion where someone bothered to implement it.

 

Starting bypasses are theoretically possible on 6 volt cars. As previously mentioned, on very old cars, Ford, Buick, Dodge Brothers, Pierce-Arrow, and possibly others had 6v systems that had a ballast resistor. Those systems ran on only part of the available voltage, just like 12 volt systems with a resistor. That means they could have implemented a bypass for starting, but as far as I know none of them did.

 

All the 6v coils i have seen that used resistors were in weird form factors, not the round cylinder with the terminals up on top that we expect to see on newer antiques.

 

 

Edited October 19, 2021 by Bloo (see edit history)

[Skolfield]

On 10/9/2021 at 4:50 PM, Ronnie said:

 

If you describe what you did to get it working it might help others with the same problem in the future.

The points were missing a piece of insulating cloth and it was grounding on the distributor.