Ignition Systems

As part of the ignition systems tasks, we had to take apart a distributor off an engine, do some measurements of the components, re-assemble the distributor and start the engine.

After I took the distributor apart, the first test I performed resistance checks on the HT leads, the rotor button and the distributor cap.
The HT leads had resistances of 3300 to 4600 ohms, which are all under the maximum specification of 10000 ohms. The rotor button had a resistance of 1 ohm and the cap had resistances of .6 to 2 ohms, which are all normal values.

Removing the distributor.

The next task I had to do was to set the distributor point gap. This gap is the gap that opens up every time a spark plug is to be fired. The specification for this gap is .4 mm. The points on my distributor were .61mm, this is too great so I had to adjust it to make the gap smaller. This is done by loosening the screws on the base plate and turning the plate to set the desired gap.
Next we had to test the performance of the vacuum advance system.  To do this, we apply a vacuum to the diaphragm. We watch the baseplate move and then see if the diaphragm holds the vacuum. With 30 mm/hg applied, the diaphragm linkage moved, and it held the vacuum, so I concluded that this system works as it should.
After I had done this, I re-assembled the distributor and statically timed it. To do this, we turn the motor over until piston 1 is 4 degrees BTDC and set the point gap so they are just opening, and then bolt the dizzy down.
When I replaced the HT leads, I tested how the mechanical and vacuum advance systems work while the engine is running. While using the strobe light, I was able to see how each system advances the timing of ignition.

The next task was to test the resistances of 2 different coils, by simply using an ohm meter to test the primary and secondary coils of each pack. The 2 coils I tested were IC-13 and CIZ-500.

The coil pack

The resistances I recorded for the IC-13 coil pack was 1.6 ohms for the primary and 6600 ohms for the secondary coil.
The CIZ-500 had readings of 3.1 and 8140 ohms for primary and secondary
These values are all within specification.

Next task was to measure resistances of ballast resistors. The 2 I tested were BR1 and BR3 and had specifications of .9 to 1.1 and 1.5 to 1.7 ohms respectively.  For the BR1 resistor I measured 1.7 ohms and for the BR3 resistor, I measured 1.9 ohms. The resistance for the BR1 resistor was out of spec, but was probably due to the wrong labels on the resistors.

The next task was to calculate voltage drops and current flow of the coil and ballast resistor in series.
Using the IC-13 coil and BR1 resistor, which both have least resistance, the coil had a voltage drop of 5.7 volts and the resistor had a voltage drop of 5.85 volts, and the circuit had a current flow of 4 amps.

The ballast resistor

Using the CIZ-500 coil and BR3 ballast resistor, which both have a higher resistance, the coil had a voltage drop of 7.64V and the resistor had a voltage drop of 4V and the circuit drew a current of 2 amps. We know that the second circuit had a higher resistance because it drew less current.

The final task was to test the trigger coil and amplifier module, out of a electronic distributor, for serviceability.
To test the trigger coil, we simply test it for resistance. The specs for this coil is .9 to 1.1 kilo ohms and ours measured 1.08 kilo ohms so this was a pass.

To test the amplifier module, we have to hook it up to a test board in which leads are connected to the module and then the machine switched on. A ticking noise shows it is working. Our module did not produce this ticking noise while being tested so this was a fail.