Short-form; Is there a way to definitively test an ignition condenser?


Long-form question; I have here a 46 Ford Super Deluxe convertible. It has the 59 A-B flatty with Ford 8BA carb and vacuum break dual point distributor. The engine was tired and gummy so I sent the long block to a reputable builder and had it overhauled, put it all back together without really doing anything to the carb or dizzy. It had been running pretty good but valves sticking open. Got it all together and it fired right up. After a few drives it became apparent that it was over-fueling so I went through the carb and got it running a bit cleaner. Gave it back to its owner.
It should be noted that while doing the engine job I also converted the car from 6V pos ground to 12V negative ground with alternator, 12 internally resisted coil from napa, resistors for the gauges and blower motor, electric cooling fan, ALL new bulbs, and whatnot. 2 gauge battery cables and an Optima red top battery make that six-volt starter spin the motor over real good.
Okay, still with me? Good. So I give this older gentleman his car back and he starts it religiously at least once a week and gets it up to operating temp but I don't think he has actually put any miles on it. So he goes away on a vacation for, I don't know, longer than I can afford, maybe a month, and next time he tries to start the car it won't start. I pulled a plug and it was black and wet. I took the carb with me back to the shop and went through it again and found no problems, put it back on along with a new set of plugs, Autolite #216, I had ordered a condenser from C&G but when I opened the box it did not look like the original, it looked like the cheapo ones that come from the box stores with points, Jap Crap so I didn't install it. and a fully charged battery. No start, not even a poof. Towed it to the shop. I pulled the distributor and basically overhauled it. The centrifugal advance was all gummed up and not advancing. reset the dual points gap after filing the contacts, which looked good, then I get to the condenser.
I have another customer with a 40 ford that still runs the flathead that I learned about the common condenser failure problem with these early systems and when I had to special order a condenser for his car I bought two. So I have that condenser, the Jap Crap one, and the Ford one that was on the car. The one for the 40 wouldn't fit and the Jap Crap looks like it won't wok already, so I get out my DVOM, put it on the ohm scale and test for continuity between the condenser body and the lead. At first touch, I see continuity that rapidly diminishes to an open circuit on both the unit for the 40 and the old one off the car. If I repeat the test it shows OPEN right away. The Chinese one has shown continuity always, 7.4m ohms. Is this a valid test? Is there a better one? Right now I have the original in the car along with a hotter set of plugs, Autolite 437, and the battery is charging as I write this. I believe it will start now as I got a couple of fires out of it earlier but the battery was pretty low, Will update in an hour, with pics! Meanwhile, what are your opinions?

Not the car I'm posting about, just some eye candy as a reward for reading this long post.

 

You ohmmeter test should be good. You are using DC from the battery of the meter to charge the capacitor or condensor. So when you first put the meter on it, it reads low because it's charging the condensor but quickly reads high as it becomes fully charged. It reads high after that because it's holding the charge. If you want to try it again, take the lead and touch it to the body of the condensor to discharge it, and then your meter should read low and then quickly high again.

Some nicer meters will have a capacitor checker built into them showing the value. But your test is a quick go-no go way to see if it works.

 

So you are saying that the two American ones, by my test are good and the unknown new one, jap crap, is no good? Thanks a million.

 

The china one showing a constant value is not good. Short it out to make sure and try it again, but if it just gives that reading all the time, it's no good. A good one will conduct and when it finally charges it will read infinity.

 

No, a DVOM can measure capacitance, but that isn't really the problem. Seeing infinite resistance on the ohms setting is better, but it still won't tell you anything other than it might work.

For a good test the "leakage" and/or insulation resistance needs checking. About 500 volts DC is applied, a DVOM, even an expensive Fluke cannot do this.

They also need to be tested at their normal operating temperature, both ignition coils and ignition condensers can work OK when cold though hork out when hot.