The motor generator which is located on the right side of the engine is the principal part of the Delco System. This consists essentially of a dynamo with two field windings, and two windings on the armature with two commutators and corresponding sets of brushes, in order that the machine may work both as a starting motor, and as a generator for charging the battery and supplying the lights, horn and ignition. The ignition apparatus is incorporated in the forward end of the motor generator. This in no way affects the working of the generator, it being mounted in this manner simply as a convenient and accessible mounting. The motor generator has three distinct functions to perform which are as follows:

Motoring the generator is accomplished when the ignition button on the switch is pulled out. This allows current to come from the storage battery through the ammeter on the combination switch, causing it to show a discharge. The first reading of the meter will be much more than the reading after the armature is turning freely. The current discharging through the ammeter during this operation is the current required to slowly revolve the armature and what is used for the ignition. The ignition current flows only when the contacts are closed, it being an intermittent current. The maximum ignition current is obtained when the circuit is first closed and the resistance unit on the front end of the coil is cold. The current at this time is approximately 6 amperes, but soon decreases to approximately 3¹⁄₂ amperes. Then as the engine is running it further decreases until at 1000 revolutions of the engine it is approximately 1 ampere.

This motoring of the generator is necessary in order that the starting gears may be brought into mesh, and should trouble be experienced in meshing these gears, do not try to force them, simply allow the starting pedal to come back giving the gears time to change their relative positions.

A clicking sound will be heard during the motoring of the generator. This is caused by the overrunning of the clutch in the forward end of the generator which is shown in Fig. 93.

The purpose of the generator clutch is to allow the armature to revolve at a higher speed than the pump shaft during the cranking operation and permitting the pump shaft to drive the armature when the engine is running on its own power. A spiral gear is cut on the outer face of this clutch for driving the distributor. This portion of the clutch is connected by an Oldham coupling to the pump shaft. Therefore its relation to the pump shaft is always the same and does not throw the ignition out of time during the cranking operation.

The cranking operation takes place when the starting pedal is fully depressed. This causes the top motor brush to come in contact with the motor commutator. As this brush arm lowers, it comes in contact with the gear in the generator brush arm raising the generator brush from its commutator. At the same time the current from the storage battery flows through the heavy series field winding, motor brushes and motor winding on the armature. The switching in this circuit is accomplished by means of the top motor brush which is operated from the starting pedal. (Shown in Fig. 94).

This cranking operation requires a heavy current from the storage battery, and if the lights are on during the cranking operation, the heavy discharge from the battery causes the voltage of the battery to decrease enough to cause the lights to grow dim. This is noticed especially when the battery is nearly discharged; it also will be more apparent with a stiff motor or with a loose or poor connection in the battery circuit. It is on account of this heavy discharge current that the cranking should not be continued any longer than is necessary, although a fully charged battery will crank the engine for several minutes.

During the cranking operation the ammeter will show a discharge. This is the current that is used both in the shunt field winding and the ignition current; the ignition current, being an intermittent current of comparatively low frequency, will cause the ammeter to vibrate during the cranking operation. If the lights are on the meter will show a heavier discharge.

The main cranking current is not conducted through the ammeter, as this is a very heavy current and it would be impossible to conduct this heavy current through the ammeter and still have an ammeter that is sensitive enough to indicate accurately the charging current and the current for lights and ignition.

As soon as the engine fires the starting pedal should be released immediately, as the overrunning motor clutch is operating from the time the engine fires until the starting gears are out of mesh. Since they operate at a very high speed, if they are held in mesh for any length of time, there is enough friction in this clutch to cause it to heat and burn out the lubricant. There is no necessity for holding the gears in mesh.

The motor clutch operates between the flywheel and the armature pinion for the purpose of getting a suitable gear reduction between the motor generator and the flywheel. It also prevents the armature from being driven at an excessively high speed during the short time the gears are meshed after the engine is running on its own power.

This clutch is lubricated by the grease cup A, shown in Fig. 93. This forces grease through the hollow shaft to the inside of the clutch. This cup should be given a turn or two every week.

When the cranking operation is finished the top brush is raised off the commutator when the starting pedal is released. This throws the starting motor out of action (Fig. 94). The top brush comes in contact with the generator commutator, and the armature is driven by the extension of the pump shaft.

At speeds above approximately 7 miles per hour the generator voltage is higher than the voltage of the storage battery which causes current to flow from the generator winding through the ammeter in the charge direction to the storage battery. As the speed increases up to approximately 20 miles per hour this charging current increases, but at the higher speeds the charging current decreases.

Lubrication.—There are five places to lubricate the Delco System:

The combination switch (Figs. 95 and 96) is for the purpose of controlling the lights, ignition, and the circuit between the generator and the storage battery. The button next to the ammeter controls both the ignition and the circuit between the generator and the storage battery, the latter circuit being shown in the heavier line as shown on the circuit diagram (Fig. 98). The button next to this controls the head lights. The next button controls the auxiliary lamps in the head lights. The button on the left controls the cowl and tail lights.

The circuit breaker is mounted on the combination switch as shown in Fig. 96. This is a protective device, which takes the place of a fuse block and fuses. It prevents the discharging of the battery or damage to the switch or wiring to the lamps, in the event of any of the wires leading to these becoming grounded. As long as the lamps are using the normal amount of current the circuit breaker is not affected. But in the event of any of the wires becoming grounded an abnormally heavy current is conducted through the circuit breaker, thus producing a strong magnetism which attracts the pole piece and opens the contacts. This cuts off the flow of current which allows the contacts to close again and the operation is repeated, causing the circuit breaker to pass an intermittent current and give forth a vibrating sound.

It requires 25 amperes to start the circuit breaker vibrating, but once vibrating a current of three to five amperes will cause it to continue to operate.

In case the circuit breaker vibrates repeatedly, do not attempt to increase the tension of the spring, as the vibration is an indication of a ground in the system. Remove the ground and the vibration will stop.

The ammeter on the right side of the combination switch is to indicate the current that is going to or coming from the storage battery with the exception of the cranking current. When the engine is not running and current is being used for lights, the ammeter shows the amount of current being used and the ammeter hand points to the discharge side, as the current is being discharged from the battery.

When the engine is running above generating speeds and no current is being used for lights or horn, the ammeter will show charge. This is the amount of current that is being charged into the battery. If current is being used for lights, ignition and horn, in excess of the amount that is being generated, the ammeter will show a discharge as the excess current must be discharged from the battery, but at all ordinary speeds the ammeter will read charge.

The ignition coil is mounted on top of the motor generator as shown in Fig. 94 and is what is generally known as the ignition transformer coil. In addition to being a plain transformer coil it has incorporated in it a condenser (which is necessary for all high tension ignition systems) and has included on the front end an ignition resistance unit.

The coil proper consists of a round core of a number of small iron wires. Wound around this and insulated from it is the primary winding. The circuit and arrangement of the different parts are shown in Fig. 97. The primary current is supplied through the combination switch through the primary winding and resistance through the coil, to the distributor contacts. This is very plainly shown in Fig. 98. It is the interrupting of this primary current by the timer contacts together with the action of the condenser which causes a rapid demagnetization of the iron core of the coil that induces the high tension current in the secondary winding. This secondary winding consists of several thousand turns of very fine copper wire, the different layers of which are well insulated from each other and from the primary winding. One end of the secondary winding is grounded and the other end terminates at the high tension terminal about midway on top of the coil. It is from this terminal that the high tension current is conducted to the distributor where it is distributed to the proper cylinders by the rotor shown in Fig. 98.

The distributor and timer, together with the ignition coil, spark plugs, and wiring, constitute the ignition system.

The proper ignition of an internal combustion engine consists of igniting the mixture in each cylinder at such a time that it will be completely burned at the time the piston reaches dead center on the compression stroke. A definite period of time is required from the time the spark occurs at the spark plug until the mixture is completely expanded. It is therefore apparent, that, as the speed of the engine increases, the time the spark occurs must be advanced with respect to the crank shaft, and it is for this reason that the Delco ignition systems are fitted with an automatic spark control.

The quality of the mixture and the amount of compression are also factors in the time required for the burning to be complete. Thus a rich mixture burns quicker than a lean one. For this reason the engine will stand more advance with a half open throttle than with a wide open throttle, and in order to secure the proper timing of the ignition due to these variations and to retard the spark for starting, idling and carburetor adjusting, the Delco distributor also has a manual control.

The automatic feature of this distributor is shown in Figs. 99 and 100. With the spark lever set at the running position on the steering wheel (which is nearly all the way down on the quadrant), the automatic feature gives the proper spark for all speeds excepting a wide open throttle at low speeds, at which time the spark lever should be slightly retarded. When the ignition is too far advanced it causes loss of power and a knocking sound within the engine. With too late a spark there is a loss of power which is usually not noticed except by an experienced driver or one very familiar with the car and heating of the engine and excessive consumption of fuel is the result.

The timer contacts shown at D and C (Fig. 100) are two of the most important points of an automobile. Very little attention will keep these in perfect condition. These are tungsten metal, which is extremely hard and requires a very high temperature to melt. Under normal conditions they wear or burn very slightly and will very seldom require attention; but in the event of abnormal voltage, such as would be obtained by running with the battery removed, or with the ignition resistance unit shorted out, or with a defective condenser, these contacts burn very rapidly and in a short time will cause serious ignition trouble. The car should never be operated with the battery removed.

It is a very easy matter to check the resistance unit by observing its heating when the ignition button is out and the contacts in the distributor are closed. If it is shorted out it will not heat up, and will cause missing at low speeds.

A defective condenser such as will cause contact trouble will cause serious missing of the ignition. Therefore, any of these troubles are comparatively easy to locate and should be immediately remedied.

These contacts should be so adjusted that when the fiber block B is on top of one of the lobes of the cam, the contacts are opened the thickness of the gauge on the distributor wrench. Adjust contacts by turning contact screw C, and lock nut N. The contacts should be dressed with fine emery cloth so that they meet squarely across the entire face.

The rotor distributes the high tension current from the center of the distributor to the proper cylinder. Care must be taken to see that the distributor head is properly located, otherwise the rotor brush will not be in contact with the terminal at the time the spark occurs.

The distributor head and rotor should be lubricated as described under the heading “Lubrication.” The amount of ignition current required for different speeds is described under the heading “Motoring the Generator.”