I had a breakdown recently due to a weak spark. I am not sure that I understand what the underlying problem was, and would like to make sure I fixed it for good. Here are the details:

The breakdown consisted of the sudden onset of misfiring, leading to an engine stall. Once stalled, the engine would not fire, but holding the coil wire near a ground while cranking showed a consistent orange spark. The spark would not appear if I opened the gap more than about 1/8”. On the roadside using an engine analyzer and a multimeter, it appeared that I had excessive voltage drop (0.4V) from coil negative to ground, and that most if not all of this drop was through the points themselves. The multimeter I had available would not give a reliable low-ohm reading, so the coil was suspect as well, because I couldn’t verify primary resistance.

I replaced the coil first because that was easier to do. The coil is the internal resistance type and sees 12V on the positive side. The new coil didn’t make any observable difference in spark quality, so next I tried cleaning the points with some 350-grit sandpaper, still trying to avoid a roadside point replacement job. The voltage drop through the points was reduced to more like 0.2V and the car was now running, but I didn’t get more than a couple of miles down the road before I had to pull over again due to heavy misfiring.

This time, I installed the new points, set the dwell to 30, and was able to drive to a safe location nearby without any more trouble. The new points yielded an obvious improvement in spark quality.

The next day, at the safe location, I wanted to be sure primary side resistance was minimized so I tested voltage drop with a different, better multimeter. This time I was showing no drop through the points, but 0.2V through the coil-to-distributor wire. I replaced that, and then both my multimeter and analyzer showed less than 0.1V drop from coil to ground. I drove about 20 miles home without any trouble after that.

Before the trouble appeared, the car ran great. Points and condenser were both new with less than 200 miles on them. It seems that the immediate cause of the breakdown was weak spark caused by bad points, as new points set up with the same dwell as the old ones “healed” the misfiring and hard starting immediately. So, why did the first set of points die so quickly?

Here are pictures of the “bad”contact points.





1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Just a guess but excessive voltage to the coil will burn the points contact

When you cleaned the points, did you recheck the gap?  Wondering if the screw may have loosened and the gap was messed up?

New condensor may be Offshore Junk. Been a lot of bad non USA made Condensors.

  

I checked the dwell both before and after cleaning the points and it was about 30 degrees.  I thought the gap seemed very small but the dwell meter seemed to say it was OK.
Regarding the possibility of a bad condenser: I have read that if the condenser is bad there will be significant arcing evident when the points open.  In my case, if it is dark I can see a pinprick blue/white spark at the points when they open.  I took that to be normal and indicative of a properly functioning capacitor.  Does that sound right?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

are you positive you are using the correct coil??

Condenser is bad



"FREE SAMPLE"

I've wondered about that, having noted a pretty strong spark at the points in testing. But, I've no long experience eyeballing point systems to make a comparison. It later dawned on me that the only way to actually see the points in this situation is with the distributor cap removed, so obviously there's no place else for the spark to go. If you've seen a few, then you'd know what is typical I guess.

Condensers (and ignition coils) are always tested at normal operating temperature. Hot. In the electronics world, a capacitor shorted to ground isn't unusual but I've been told this doesn't typically happen with ignition condensers, due to the high current involved, they tend to go "open" and probably intermittent, as they come up to temperature.

Shorter answer is ignition condensers need to be tested for insulation resistance at around 500 volts DC, the modern digital "capacitor checkers" simply can't do this. Defective condensers can be weeded out with these, but that's only part of the story. A healthy capacitor will charge up and hold high voltage for a very long time, at least a day or two. I noticed this in comparison testing some suitable high voltage modern poly film caps. My stable of NOS or junk box "pulls" appear to pass the high voltage leakage tests cold but they are no longer able to retain voltage for any length of time. In rainy weather or high humidity I bet it would cause trouble, also under severe service.

I don't ordinarily run points any longer but do have a spare points distributor setup w/ tested condenser and spares. This is a weak spot for the DIYer without access to the right test equipment. We tend to think of new ignition parts = good parts, and that isn't true, not with condensers, and we also tend to think of NOS parts = good parts, and that isn't necessarily true either, for different reasons. They are getting older and degrade just sitting on the shelf.

I am not positive about the coil.  The car was rewired with an EZ mini 12 circuit harness before I bought it.  The coil bore no brand identifiers, just a blue can with markings stating that an external resistor was not required and a 4-digit number that doesn't seem to cross-reference with any part numbers I could find.  The coil I replaced it with was the closest thing I could find at the local parts store: Carquest EBC1487.  I have considered using a stock coil and adding an external resistor so that I could be sure, plus get the 12V starting boost from the solenoid, but as it is I am able to start in freezing weather just fine.  

Tedster, when I was cranking and observing the points I had the coil-to-cap wire plugged into the coil and grounded, so the spark did have somewhere to go (if I understood your comment right).  

I did buy a spare replacement condenser to install in case of a repeat breakdown.  I don't like to think it's 50/50 whether a new condenser will be good, but I have the impression that is a common perception, so maybe that's how it is.

One other variable I wondered about with regard to the points failure was whether I might have over-lubed the point cam.  The factory manual calls this out as a possible cause of burned points.  To my eye the points and surrounding area look totally clean though.

I drove the car about 75 miles today with no ignition trouble at any time.  Perhaps this weekend I'll take another look at the points for signs of premature wear.  

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

It looks like you probably have a good condenser since the car is back on the road with the same condenser.  Since it's a points system, just by design it's designed to run with a resistor in the circuit. The original Ford yellow top coil of the day had a primary resistance of about 1.5 ohms and about that amount again for the resistor.  This keeps the current through the points at a level for which they will be happy with for many thousands of miles.  That coil you had that stated no resistor required was probably for some form of electronic ignition system.  You didn't stae what the primary resistance of the coil was but it may have been low enough to cause excessive current/heat for a points ignition.  Just a thoght - hope it helps.............

64F100 57FAIRLANE500