Introduction to the Distributor

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Following are links to the sub-topics discussed under the general heading of "Distributor" -

Note: All but the first are links to other pages on this or other Web sites.

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Introduction

To paraphrase John Muir* -

Recapping "Ignition" - Look to a little left of the center of the engine and find a brown or black round plastic thing with five heavy wires sticking out of it. That's the Distributor Cap.

Under the distributor cap is the Distributor, and inside the distributor are the Rotor and the Ignition Points. The Condenser, a small silver cylinder, is attached to the outside of the distributor (sometimes located inside the distributor).

There may be a bright metal biscuit, about 3" in diameter, on the side of the distributor with one or two metal or rubber hoses leading out of it; this is the Vacuum Advance. If you don't have this biscuit, your distributor is a centrifugal advance type. These two distributor types (and variations) are discussed in more detail in John Connolly's technical article on Choosing the Right Distributor.

When the ignition key is turned on, electrical current goes from the battery to the Ignition Coil, usually mounted on fan housing. Inside the coil are thousands of turns of wire, which increases the voltage to something like ten thousand volts. This high voltage is sent to the distributor from the center large outlet on the coil to the large connection in the center of the distributor cap.

Note: The coil also has two side connections where smaller wires are either bolted or push-on connected. On one side is a thin wire that goes from the coil to the distributor (usually green); on the other side are a wire that brings juice from the ignition switch, a wire that goes to the automatic choke, a wire to the carburetor cut-off jet, and a wire to the back-up lights.

The function of the distributor is to send high voltage spark impulses to the spark plugs at exactly the right time so that they fire at the top of the compression stroke and ignite the compressed fuel/air mixture, drive the pistons, and provide power to the car.

The Distributor Shaft (which is nearly square inside the distributor) is driven round and round by a gear on the crankshaft. At each point of the square the distributor shaft opens the ignition points.

In between the high places the points close. When the points are closed, the twelve volt current (or six volt in older VWs) from the key is built up to high voltage in the coil. Then when the points open there is plenty of voltage to make the spark jump from the rotor to one of the four pins inside the distributor cap and on through the heavy wires to the spark plugs, providing a hot spark to burn the compressed fuel/air mixture in the cylinders.

- How to Keep Your Volkswagen Alive -- A Manual of
  Step-by-Step Procedures for the Compleat Idiot,
  1976 Edition, page 14.

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Again, please see the links above for more
information about the distributor.

 

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