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What can cause a condenser to fail?

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Hey fellas,

**Non-sufficient point gap-

**Too close to engine heat


I am running a Mallory Dual Pt. Distributor from motorsport on an L28 in my 240Z. (P.S. I wouldn't let go of my old engine. It's in my garage on a palet, and completely wrapped in shrink wrap). No way I,m giving up that L24 block for a measley, very measley core charge. I also added an MSD Blaster coil with balast. The dist. came with a condenser that failed me not long after I upgraded my alternator. Don't think the alt. is at fault as it is a ZX alt./internally regulated. The car does not show any other classic signs of an overly hot alternator. Bulbs, fuses, wiring all seem great Seems like the regulator is doing it's job very well. as a matter of fact the car is running like a bat... My main indication of trouble occurred two nights ago as I was listening to that engine humm along at about 45mph when out of nowhere, it backfires in rapid succession. After that it was fine until I returned home 45 Min. or so later. Next day seemed great then POW!...POW!, and It wanted to stall as I was turning easily out of a street in my subdivision. I was able to save it by choking it back to life, and got her home.

I'm willing to bet that one of youz guyz has seen this before...huh?!?

Maybe my first real indication of trouble was when it skipped 2-3 times while my son and I were cruising along at about 60; it skipped (and made the tach drop and jump twice very quickly. That screams ignition to me and coupled with the backfiring it seems like ANOTHER condenser... If so , there must be something that I have done or maladjusted to cause the car to devour condensors. Any suggestions anyone?!?

Thanks loads!


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Maybe It's nothing you've done, maybe it's just gone south (failed)! It's just an electrical component and they are susceptible to failure. Have you installed a new condensor (with new points, adjusted), to see if that fixes your problem? You didn't mention how old or how long these points and condensor have been in service. Just a thought!

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Electrolytic condensors (capacitors) are prone to dry out and fail. They are filled with a dilectric grease or gell. Engine bays are a nice hot environment and although the caps are designed for automotive use, they will fail after time.

They are cheap to replace so maybe have a couple in the car as spares just in case.

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Its very unsettling to think you have no control over when one of these things might sputter and quit. I have seen new condensors start to stutter and miss, right in front of me on the dyno. Put another one on and it might last five years, or five minutes. I have a theory. I think that inside those little metal containers are some very tiny women. Sometimes they work fine without any attention at all. Then, for no reason, they'll spit at you and quit. Can't trust em'. Condensors I mean.


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Maybe that's why they named them..."Condense-Hers" instead of "condense-hes". I mean if you tend to keep them boxed in, they CAN get grouchy... HA!

On a serious note, I am only getting 2-4 weeks out of them. I am one of those running a ZX alternator, and a MSD Blaster. Can this spell condense-her trouble?


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  • 2 weeks later...

Hi 72'240

Your problem with condensers (capacitors) sounds a little spooky. Here are some thoughts.

Why do you need a capacitor on the distributor in the first place?

Answer: The primary of your ignition coil is opened by the distributor contacts and when this happens the magnetic field in the ignition coil collapes and creates the high voltage for your spark plugs. At the same time a high voltage spark occurs across the open distributor points. The cap. acts as a low resistance path to ground attempting to do three things.

1. reduce pitting on the contact point

2. reduce electrical noise imposed on the 12vdc engine system. (Ever hear buzzing noises in your radio that vary with engine speed)

3. The most important one. Allow the magnetic field in your coil to collapse quickly to produce the spark

The cap then acts like a resistor. Voltage drop across it and some value of current shunted to ground thru it.

Capacitors die easiliy

Exceed its temperature rating.

Exceed its voltage rating

Exceed its current rating

All of these things can lead to failure of the capactor dielectric and turn the cap into a shorted one. No capacitor-no spark!

What to do, What to do.

Try to get the manufactures specifications for the cap and see if it will work with the Mallory dual point distributor and your MSD Blaser coil. The blaser coil may be creating too much kick back voltage. I assume that the capacitor did not come with the distributor. Also ask MSD what capactor they might recommend.

Make absolutly sure that one side of your capacitor is connected to a really clean chassis ground.

Good luck

Oops! Should have read your post a bit more carefully. The cap came with the distributor. So this might be a marriage problem. Talk to MSD first.

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On my old dual point set up I had 2 condensers, 1 per set of points. You don't mention how many condensers you have. I would think with only 1 you would be working it twice as hard and this would lead to failure.

Just a thought.

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It has been my recent experiance that the "new" condencer you are buying is really an old one, sitting on the shelf for maybe years. Time in itself is an enemy to them. With most cars having switched to pointless ignition many years ago there just isn't a serious turn around of shelf stock and so the part you are buying today may be 10 or more years old. I went through 3 in 2 days last year, one bad out of the box, before I tossed the dizzy and went pointless. You may want to try a different source, maybe someone has something newer on the shelf.

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Wow, thanks folks. Lots of great thoughts and ideas. Please keep em coming. A truly good education. The speed shop that sold me the MSD Blaster 2 with balast resistor included, told me that the MSD was great with the Mallory dual pt. Oh well!

Keep em comin! Thanks!

72 240z

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