Quiz

[Friartuck]

OK folks, thought this was a good opportunity for an old fashioned diagnostic quiz. Symptom was intermittent spark from the coil on a 6 volt 1951 Caddy. Can you spot the problem?

 

 

Edited September 28, 2018 by Friartuck (see edit history)

[Frank DuVal]

I spy broken insulation. Especially the taped over area on the right side. Replace those wires. The other issue is the "hot" and "ground" wires are twisted together. If the insulation has failed there, that will also cause intermittent issues, until they become permanent.

 

Is that a broken wire going to the brass lug on the left side? I blew the picture up, but could not see a definitive break.

[cahartley]

I don't like the looks of the  "connection" at the left.

[Friartuck]

These are good guesses, but not the main problem. Yes the cloth covered wire is disintegrating and the two wires look like that are twisted, but there is still a more fundamental problem. Hint: You're on the right track.

[Stude17]

It looks to me that the earth wire for the breaker plate is wrapped around the wire from the coil which to me is poor workmanship.  Also the insulation on the coil wire terminal where this happens looks particularly suspect.  Is earth wire  attached to the vacuum advance arm?   If this is the case this could be the source of the intermittent spark when the vacuum advance operates.

[hchris]

Looks to me like the vac mechanism is causing a ground of the primary wire when it moves the plate.

[Friartuck]

Ding Ding, Ding Ding, we have a winner. Gold Star to Stude17.  Answer is the ground wire was attached to the advance pivot. And this was done some 15+ years ago by a professional shop. Using new wire and attaching to the condenser screw solved the problem. While it looks like the new wire is resting on the advance arm, its higher and not touching. Customer called last night and after reinstalling the distributor, the vehicle started on the first attempt.

[RansomEli]

Good thread and pretty quick deductions by the group. I've had a couple problems in the past that were ultimately traced back to a short in the distributor.  One of them involved a person who did not replace a fiber insulator washer, then asked for help when his Austin Healey didn't start. After several hours of insisting he absolutely replaced everything just right, my buddy found a fiber washer laying on the garage floor. Oops. 

 

Replaced the washer and the car started right up. 

 

Never trust anybody when looking at the distributor.

[Curti]

This is currently posted on the ACD website. 

  :

"My Auburn was starting OK, but then stalling right away. I made a guess that the condenser was bad and decided to replace it. Unfortunately, when I asked for a 6 volt condenser at an auto supply, the clerk had no idea what I was talking about. Went on-line and found what I needed, and within a few days received a new Mallory 6 volt condenser. Now the engine runs perfectly. Learning experience: condensers must go "stale" after sitting on a shelf for 10 years."

 

 Is this true ?

[trimacar]

I just went through the same thing, looking for a condenser for my Pierce.

 

You have to look at applications, not voltage.  Condensers apparently aren't sold based on voltage, and that's why the clerk may have been confused.  Asking for a "1953 Chevrolet six cylinder condenser" will produce results.

[c49er]

Remember a special fine gauge, high strand count, and very flexible wire is used in distributors.

All because the vacuum advance is constantly moving the breaker plate.

[Mikefit]

Condenser s don't know voltage 6/ 12 does not matter just my .2$ Mike

 

[Friartuck]

c49er makes a good point, very flexible wire is one that has many strands of fine wires twisted together. This repair used a multi strand wire and is good enough for this application. Regarding condensers, generally there is no voltage limit. There is a possible age issue, as older condensers with a paper insulator between the foil sheets can become brittle and/or break down and either 1) reduce the condenser value, 2) short it, or 3) open up the connection of the foil sheets inside. newly manufactured condensers typically use a Mylar or acetate insulator.

[Frank DuVal]

Are you saying the black screw holding the advance arm to the breaker plate is NOT TIGHT, but loose to allow swiveling?  Therefore the ground lug under the black screw was not always "ground"?

 

Not knowing that should be loose, I thought the pull on those wires when the advance arm moves the plate was causing a short (not a "long") from grounded to hot wire.

 

I use test lead wire for making points leads. Veeerrry flexible.

 

There is a voltage limit to a condenser (capacitor), but 6 vs 12 isn't it important since the kickback voltage (when the points open) is hundreds....

 

Mike, your comment was closer than 2 cents, as your name is Mike. I am of course referring to the slang term for microfarads, the measure of capacitance, "Hey, I need a 40 Mikes  (mics) electrolytic ". 

 

The capacitor, um condenser,  is a tuned circuit with the inductance of the coil. Therefore the farad (micro, micro micro (pf for the under 50 year olds) or Nano for you new guys)  rating of the condenser is the important specification. Voltage will never be mentioned in ignition circuits. The farad rating of the condenser affects the wear of the points, as it affects the current in the circuit.

 

Paper capacitors get moisture in them (paper insulator absorbs water when the wax fails) and causes low resistance or "leakage" failure between terminals. Mylar and polyester insulators much better. Some can go bad sitting on the shelf, others work for years. You can test them, with these new Fluke (or other brand) DMMs. Check the Farad rating, and if that is in range, check the resistance. It SHOULD be infinite or at least megohms.

[Friartuck]

The black screw was not tight and the post/connection was poor (friction fit). Other comments on condensers are spot on.

[Frank DuVal]

Yep, that makes an intermittent!

[John_Mereness]

On 9/28/2018 at 11:47 AM, Curti said:

This is currently posted on the ACD website. 

  :

"My Auburn was starting OK, but then stalling right away. I made a guess that the condenser was bad and decided to replace it. Unfortunately, when I asked for a 6 volt condenser at an auto supply, the clerk had no idea what I was talking about. Went on-line and found what I needed, and within a few days received a new Mallory 6 volt condenser. Now the engine runs perfectly. Learning experience: condensers must go "stale" after sitting on a shelf for 10 years."

 

 Is this true ?

Condenser seem to be quite the problem these days - I always travel with a couple (because you cannot count on one out of the box always working like it should)..    If at a good auto part store you can always ask for a condenser for a 1952 Chevy  (a 6V car that seems to be something commonly indexed).  Also, if at a NAPA store I generally ask for one for a 1941 Cadillac (what I am running in the Auburn 851). 

[PFitz]

I've always avoided NOS condensers because the insulation can break down over the years. However, the new condensers for 6 volt systems (48-53 Chevy 6 cyl) have not been consistent quality for at least a decade now. I've had a several quit after only a few miles and one that was DOA.  As such I always buy then in twos just in case.  I advise all my customers to carry spares and when the ignition system starts to act up, first try swapping the condenser as the most likely cause. Just this week had one case like that in Connecticut that the owner had to do that with a fairly low modern mileage condenser.

 

Paul

[mikespeed35]

A friend of mine was on a tour and one car had trouble and my friend diagnosed a condenser. He happened to own a NAPA store but on the road had to shop at one of his competitors. He went in and told the young man he needed a condenser. The young man asked for the application and my friend said any cond. will work just get me one. The kid come back with a big box, air cond. condenser!

CORDiallyMike

[edinmass]

FYI- the make solid state condensers for more than twenty five years, and they are very reliable. We use to sell them in our motorcycle dealership. I haven’t put one on a car in years.......

[Frank DuVal]

OK, Ed, show me a link to a solid state condenser. Maybe you mean solid state points? Like Pertronix?

 

Yes, I did Google solid state condenser, and all I got was links to microphones.

 

There are active capacitors in electronics, but I have never seen one in automotive applications.

[DonMicheletti]

That connection is just fine. That screw attaches directly  to the breaker plate and will make a correct circuit. Of course it must be tight as mentioned.

My Roadmaster has been that way for over 30 years (and as I got it).  Yes, the fine strand wire insulation is frayed, but that makes no difference - it is a ground.

[Friartuck]

Don Micheletti makes a valid point that the screw is well attached to the breaker plate. His screw may have a spacer where the screw can tighten (to the plate) while leaving the advance arm to pivot. The issue in our case was the screw was into a threaded pin and the diameter of that pin didn't make a good connection to the underside of the terminal even when the screw was tight. We opted for a sure thing, the condenser mounting screw (ample connection on both sides of the ring terminal).

[edinmass]

On 10/7/2018 at 11:20 PM, Frank DuVal said:

OK, Ed, show me a link to a solid state condenser. Maybe you mean solid state points? Like Pertronix?

 

Yes, I did Google solid state condenser, and all I got was links to microphones.

 

There are active capacitors in electronics, but I have never seen one in automotive applications.

 

Hi Frank, I wasn’t referring to an electronic ignition, back in the 80’s the Harley Davidson aftermarket companies came out with a solid state condenser replacement. We sold them at our motorcycle shop, they were about twenty dollars back then. They were small, and worked fine as a universal replacement that “would last forever”. They were about the one third the size of a postage stamp, and had several different length leads on them. We used them extensively back in the day. I’m sure they must be available somewhere now. Ed

 

Google ....... easycap ignition condensers.......similar but different, a ceramic solid state condenser replacement.

Edited October 16, 2018 by edinmass (see edit history)

[Friartuck]

I think what Ed is referring to are a class of capacitors used in the electronic industry called Ceramic Surface Mount Technology (SMT). The term Solid State threw me off as well. Due to the multi-layer construction and ceramic composition, they are rated for 600+ Volts at the needed .22 uF value. They can provide a series of solutions where space is at a premium, such as in a motorcycle ignition. This is good to know.

[Frank DuVal]

OK Ed. Those are just condensers. Aka capacitors. Same item, different term. Ceramic capacitors have been around since the 20s. Just technology evolved to where they make them in larger values today. 

 

Ceramic does not absorb water like the paper insulator in old fashioned ignition condensers, so I can see why there are better. Mylar and polyester are better than paper, not as good as ceramic typically. One can use a good old Sprague Orange Drop capacitor of the correct value if it fit in the distributor. 

 

Solid State refers to silicon/germanium type substrate active devices. I.e. not vacuum tubes. ?

 

[Joseph P. Indusi]

I agree with Frank DuVal's earlier post that the capacitor in series with the primary of the coil forms a series resonant circuit when the points open.   If the capacitor value is correct it will form a resonant circuit with the coil primary and the voltage across the coil primary will be an oscillating voltage much higher than 6 or 12 volts.   This will cause a higher voltage to be induced in the secondary to fire the spark plug.

So the microfarad capacity of the capacitor is the important factor.

Feel free to comment.  A very interesting thread and thanks to Friartuck.

Joe, BCA 33493