Condensers do go bad, for a lot of reasons, but usually they are born bad,
or have a flaw that will make them fail. Their failure mode is to short out,
but usually it's not a dead short, just a breakdown in the dielectric
material that insulates the two conductor plates.
Time was we tested those things--every shop had a coil tester and a
condenser tester. Now they are hard to find. It's worthwhile to carry a few
spares and test them BEFORE you put them in your spares kit to make sure
they are good. If they are bad you'll have a very weak spark. It's also
worthwhile to higrade a bunch and pick the best ones.
A continuity check with an ohm meter won't cut it. What you really want to
do is test them at operating voltage which is about 400 volts usually (the
coil's inductive kick on the primary goes that high). On the old testers
it's a go-no go, with the needle pointing to the red zone for bad
condensers. As I recall the test is actually a conductance test, showing
dielectric breakdown as leakage current.
Condenser (capacitor) testers were the bane of gunk's existence (gunks are
gofers or parts washers at motorcycle shops). The evil mechanic (me) would
charge up a condenser to 400 volts and toss it to the gunk. Or reach over
and touch the leads to the back of their neck. Either way was quite
entertaining. It made for a lot of very alert and suspicious gunks.
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of Joe Boruch
Sent: Wednesday, August 10, 2005 5:48 PM
To: fot@autox.team.net
Subject: Re: Engine won't run
Thanks for all of the suggestions about my engine problem. I think I found
the problem - 2 bad condensors. One was new this year the other was from
last year. Not sure why they are failing. I also found that the spring for
the (new this year) Mallory points are also much weaker than the ones I
have used in the past. Maybe with the weak springs the points were floating
and causing the condensor failures? Any ideas on why condensors would fail?
They check ok with an ohm meter. They give the typical capacitor kick.
After my spare distributor worked in the car I swapped the points and
condensor on my old one and it worked. I noticed then that the new points
that had been in the car had such low tension. After the car ran with the
replaced points and cond. I put the old cond. in and it barely ran. I put
the working cond. back on and it barely ran - now what? Tried again and it
finally caught. A plug or plugs must have been fouling so it was taking
time for them to clear. I even put the coil on that I thought had failed at
the track on and it works. I swapped condensors a couple more times and
wound up with 2 that the car would barely run with. The car keeps
starting/runnig fine with the replacement points and condensor. Joe(B)
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