Technical The condenser, its always the condenser

Ok, not always but it seems to be the most common cause. My truck started running bad, The engine would stop running for a fraction of a second, then jerk violently back to life. I made it 35 miles and it quit completely. I had a good spark to the points and they are gapped correctly. 1000 miles on the distributor cap, new sparkplug wires. My assistant said he saw spark at the end of the spark plug wires so it came home on the trailer.
At home I found NO spark at the plugs but still had a good spark at the points. I replaced the condenser only and it fired up. I think I will carry a condenser with me.

I opened the bad condenser and looked inside. It was black where the copper wire meets the aluminum foil thats rolled up inside.

 

I remember the days when the condenser was seldom changed. It's a shame that quality has been lost.

 

They were replaced with every set of points, usually about 10000 miles. Very few, in my mind, needed it but while you were there it was easy insurance. My '24 DB has what could be the original condenser and it gives no trouble. But I keep hearing of the new junkers crapping out.

 

If you can get a copy of the V-8 Times from Sept./Oct. 2014 there is a very informative article on condensers.

 

You could try one of these, about a buck. They are reliable.

 

Such a simple part but you are right, the majority of the time the condenser is the culprit. HRP

 

Is there a bench test for a condenser?

 

Charge one up by putting the base to ground and touch the wire to positive on a car battery.

...now set it on the parts room counter at the auto dealership, and the next mechanic that comes to the window would eventually pick it up while waiting for his parts...and ZAP.. get a good wake up shock.

.

 

Yep, twice here...

 

Ha! Ornery!

 

Hmm. Ok. What is that? What do I look for in the electronics catalog?

 

In the name of sharing...2 weeks ago just heading to a car show in Penticton in my roadster. For me, that means catching a ferry, stop at the first available gas stop and then down the road we go. Pull in and all is well, gas up, re-start and suddenly I'm running on 4 cylinders (Harman Collins dual coil on the flathead). Quick roadside diagnosis, I've lost one side of the distributor...limp home on 1/2 an engine. Couple tests later, as you say, it was one of the condensors. Cut it open to find a disconnected solder joint (the condensor was old enough that it had been soldered...and made in the USA!

Did a bit of online research and it seems the Porsche guys don't seem to complain too much about their Bosch manufactured condensors so I decided to give them a try (I don't recall the part number off hand but they were for a late 60's or early 70's era Porsche 912). There was an online website showing a bunch of new style condensers cut apart and the Bosche version seemed to have better contact areas than most.

I too will be carrying a spare.

 

I have these available. .22 microfarads (perfect for standard points ignition), made by putting a modern severe duty film capacitor (good to 1000 volts and 300 degrees C) in a custom case that looks like it should. Granted, they have to be mounted on the outside of the distributor, but that just makes it look like you have a fancy dual point setup. All guaranteed to be within 10 nanofards of the nominal value and warranted for a year. The originals are now almost impossible to find and usually have split cases if you can find one. Contact me if interested.

 

Will they work on Ford 1957-74? Whats it called and where can we get them?

 

Ok tubman, what is a film capacitor,how much does it cost and where can we get'em?

 

You can buy an orange drop or mylar capacitor (condenser) from any electronics supplier. Look up the specification for your car, probably about .25 microfarads. Get one rated for high voltage, like 400 or 600 volts. You don't really need it but they are better. If it won't fit in the distributor you can mount it on the coil at the other end of the wire that goes to the points. It will work just as well. Millions of motorcycles and some cars came this way.

And yes they are that cheap, a buck or so.

 

these? https://www.ebay.com/itm/Qty-2-Elme...652807?hash=item1ed23429c7:g:vEMAAOSwVTNbLzdG

 

A film capacitor is the latest technology available. I don't really understand it completely, but my partner (who is the electronic brains behind this project) assures me that they are what we should be using. The only thing I know is that they are rated to take voltage spikes up to 1000 volts and will not break down at temperatures under 300° centigrade . This means they will work fine on 6 volt systems with generators. I have had one on my '51 Ford with an engine equipped this way for two years and everything runs fine. I have had them in the field for two years now with no reported failures.

That's the good news. The bad news is that they are very labor-intensive to make in the quantities we are producing, so I have to get $75 each for them. When you consider the alternatives (running a wimpy looking condenser that is probably foreign made and unreliable or trying to find an unsplit functional original) these are a reasonable alternative. If you're still interested, you can PM me here.

 

Yeah, good luck with those. I've already been down that route. The capacitors we ended up using are about 1/2" in diameter and about 1 1/4 inches long and cost a lot more than "about a buck". The smaller ones just won't cut it long term.

 

There wasnt much in the one I took apart today. I've made capacitors with a sheet of glass and aluminum foil for a Tesla coil.

 

the problem with the normal automotive condensers seems to be the connection inside, to the can or to the wire.

I had this problem a couple years ago, too.

I used a modern coaxial .22 uF at 1000v replacement, it's ugly (sits outside the Mallory dual point), but the blower does a good job of hiding it.

Put a normal lab oscilloscope on the primary side of a point ignition system some time, just for fun, see how high the voltage spikes. 100v rating is not enough!

edit: also, it's hard to test for an intermittent problem on a condenser, which is how they usually fail--- starts with an occasional miss, gets worse over time, maybe.

 

What's a nanaloid? Probably like my son tells me. It won't mean much to you

 

The bench test is an ohmmeter. Touch the leads to the condenser, then switch leads and touch the condenser again. A good one will show a little kick when you reverse the leads

 

Sorry Jim, I meant 1000 volts. I had a typo in my original post that I have since corrected. And you are correct; my first attempts were with capacitors in the 200-300 volt range. They all eventually failed in testing.

As to my pricing : $10 to make it run good; $65 to make it look good. I know that sounds a bit out of proportion, but at least it ain't billet aluminum.

 

I had a devil's can with a loose wire.
Looked, and looked for an intermitant problem.
Then changed points and the condenser, I touched the condenser and the wire fell off.
There it was.

 

Do your brass ones come with the clamp?

 

Yep; and a 12 gauge fabric covered 2 1/4" lead with the proper "flag" terminals. Just like in my first picture (which is an '51 Oldsmobile "Rocket" distributor with a Mallory dual point conversion).

 

This is useful only as a preliminary test; it will only tell you if it is completely shot or not. There is such a thing as a capacitor tester that will read out the actual capacitance in the proper unit of measure (micro-farads and nano-farads in automotive condensers), but not many people have them. My partner does. Then there is also the effect of heat on them; a lot will fail under normal engine heat while still reading good at room temperature. As has been said, nothing is simple any more.

 

No, those particular examples there are being sold today as NOS mainly as audiophool capacitors. I'm not sure if they are polyfilm or paper inside as dielectric. Probably poly, but. The voltage rating may not hold up. The really old school capacitors were made with paper and foil roll and then dipped in beeswax. Anyway those in the link are only rated at 200 volts.

Modern polyfilm capacitors are much better than in years past for any given voltage rating. My shop manual specifies a capacitance .21 to .25 microfarads, or MFD, this is called µF today. (Periodically, engineers change the nomenclature to sow confusion to those Not Of The Body) They don't list a voltage rating but it's higher than you might think.

The available standard cut today is 0.22µF; I would take Tubmans advice and go with high voltage, although I believe a 600 volt "orange drop" should be fine. 716P Sprague (Cornell-Dubilier) is a high quality Polypropylene film capacitor, non inductively wound, high pulse current capable, epoxy coated with plated copper leads. Temperature rated 221° F (105C)

For all that though, just use an NOS ignition condenser from "back in the day". They are inexpensive to buy because they are not rare, and you probably have one in your junkbox anyway. They were made well. While some changed the condenser with every points change during a tune-up, a lot of guys would leave them in if everything was otherwise straight in the ignition. Even then, a bad condenser wasn't unheard of. The really old stuff, say before the mid 1950s, may have trouble even if NOS. If a condenser was made with paper as a dielectric it will start to degrade (like old newspaper) or the can has absorbed moisture and corroded, etc.

To test any capacitor it really needs to have its rated voltage applied. A multimeter won't do this, they check for the capacitance value, which is next to useless mostly. Testing for leakage (shorts) and ESR. They will sometimes work OK when cold but breakdown under heat.

 

and as I mentioned, the usual problem with the automotive can type condensors is an internal intermittent connection. The way they are built, there is not a "real" connection from the film to the can or wire, it's just contact held in place by the tension of the rubber insulator plug around the wire lead. Pretty crappy design.

when you bench test it, it works. when you're driving down the road, it will misfire occasionally. when you go down the dragstrip, it will misfire more.