So what exactly does the capacitor on the ignition/distributor do? I bought a new one, just in case.

Brit

------------------
If you ever have a questions about the sincerity of the circle of Fiero owners on this site, take a look at:
"In Memoriam: Fiero Members"

Pretty impressive.....

Avatar is of an actual Fiero on fire

If you're talking about a Fiero and you mean that little silver cannister looking thing, that's not a cap. but rather a tach filter.

quote Originally posted by Phil: If you're talking about a Fiero and you mean that little silver cannister looking thing, that's not a cap. but rather a tach filter.

Oops! Ok, what does that do?

------------------
If you ever have a questions about the sincerity of the circle of Fiero owners on this site, take a look at:
"In Memoriam: Fiero Members"

Pretty impressive.....

Avatar is of an actual Fiero on fire

You must not have a stock engine in your Fiero. Mine has electronic ignition and thus no capacitor, also called a condenser.
In the old days, the condenser built up a charge and then released a short burst to the coil which bumps up the voltage and sends it back to the distributor to be distributed to the spark plugs. The timing of the released burst was controlled by the points running on a cam on the distributor shaft. The points were mounted on a plate that rotated slightly, driven by a diaphragm connected to the intake manifold, to adjust the timing according to manifold pressure. The rotor and distributor cap saw to it that the spark went to the correct cylinder.
A different capacitor can also be used to reduce radio interference and may have been added on to your system for that purpose.

The "tach filter" is used to filter noise spikes on the signal line to the tach.

[This message has been edited by StockGT (edited 05-19-2008).]

Keeps tach RF noise out of the radio.

quote Originally posted by gem1138: In the old days, the condenser built up a charge and then released a short burst to the coil which bumps up the voltage and ...

You seem to be describing a capacitive-discharge ignition system, which didn't come into commercial use until the 1960s. The real function of the condenser (i.e. capacitor) in a conventional Kettering ignition system is to minimize acring as the points open and the magnetic field in the coil collapses, thus extending point life. It was not intended to "build up a charge" to release into the coil.

To address the original question ... Yes, that's the tach filter, not an ignition condenser. The function of the tach filter is to assure that only a single pulse is delivered to the tach for each spark event. This helps to ensure tach stability and accuracy.

[This message has been edited by Marvin McInnis (edited 05-20-2008).]

When I dyno'd my car, I found out the tach was reading several hundred rpm faster than the actual engine speed. I got a new tach filter and when I dyno'd a second time it was almost bang on with the dyno.

A 20 year old electronic bit is sometimes good to replace even if it works.

Arn