Distributor - 1929 Model U
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The distributor, which is of the single breaker arm type
with condenser on the outside of the base, is accessibly mounted above the
timing gear case and driven through a shaft from the camshaft. The opening of
the breaker points by the cam on the distributor shaft interrupts the flow of
primary current, which induces an electro-motive force in the secondary winding
of the coil, mounted on the dash. The high-tension current is delivered to the
center terminal of the distributor cap, and thence through the rotor to the
spark plugs. The cylinders are fired in the order 1-3-4-2.
To Adjust Point Opening
The rotor should be removed and the engine turned until the
breaker arm rests on a high point of the cam. The gap should be .020" and may
be measured by standard feeler gauges. If necessary to correct the adjustment of
the gap the lock screw on the contact plate should be loosened and the adjusting
screw turned as required. (Fig. 12.) The breaker arm should move freely on its
pivot and it is advisable to check the tension of the breaker arm spring.
Ignition Coil
The ignition coil needs little attention other than to be
kept clean, dry, and well grounded. All terminals on the coil must be tight.
Spark Plugs
The gap between the spark plug points must be .027" to
.030". Too wide a gap will cause misfire, especially at high speeds and when
laboring with open throttle, while a small gap causes poor idling. Dirty or
fouled spark plugs should be washed in gasoline. Uniform gap setting insures
evenness of engine firing.
The porcelain on the top of the spark plugs should be kept
clean at all times. Oil or dust on the porcelain will cause leakage of the spark
and in damp weather may prevent starting. Present day engines develop high
compression and very high speed. This severe duty imposed on the spark plugs
causes erosion. It is, therefore, advisable to replace spark plugs at intervals
of every 10,000 miles of service. The installation of new spark plugs, properly
adjusted, will have a marked effect upon the performance of the engine and aid
materially in keeping the engine in condition for smooth flowing maximum power.
The engine performs best with the spark plugs furnished
with the car. These are obtainable from Plymouth Service Stations and should be
used to the exclusion of all others. The use of so-called carbon-proof spark
plugs and others having smaller diameter electrodes should be avoided. Such
spark plugs will cause the engine to miss on heavy pulls.
Suggestions
Ignition trouble will make itself known by the engine
misfiring or refusing to start. If the engine misses regularly on one
cylinder, the trouble is usually clue to the spark plug in that cylinder being
dirty, broken or improperly adjusted. If misfiring is not limited to one
cylinder, the cap should be removed from the distributor and the contact points
examined to make certain that they make good contact with each other and are
clean. The correct point opening is .020". If the contacts show a tendency
to burn, the distributor may not be well grounded to its mounting bracket. Paint
and dirt should be scraped off the bracket to insure a good ground. The
condenser, which is on the distributor, should be tested and its connections
from the distributor should be tight. When the engine will not start, the
ignition should be checked as follows:
The ignition switch should be turned "on" and the cap
removed from the distributor to see that the contact points are touching each
other. Then the secondary wire should be disconnected from the center
terminal of the distributor cap and held about
1/8" from some metal part of the engine. The contact points should
next be separated by moving the breaker arms with the fingers. A spark should
jump between the end of the high-tension cable and the metal part of engine, if
the coil and its connections are in good condition. If no spark is
obtained under the above conditions, it should be determined whether current
passes through the coil.
A quick check may be made on the primary circuit of the
coil by closing the ignition switch and cranking the engine. If the ammeter
needle moves bark and forth between 0 and 3 or 4 amperes discharge, it indicates
the primary circuit is all right. If ammeter needle does not move, the following
procedure should be observed:
With the ignition switch turned
"on" and the distributor contact points separated, a screwdriver should be
rested over the edge of the distributor housing with the end of the screwdriver
touching against the breaker arm. There should be a flash or spark to indicate
the flow of current. If current flows, the secondary winding of the coil is
apparently damaged and a new coil should be installed. If no current can
be detected on this test, the small wire from the coil to the distributor should
be examined for breaks, loose connections, or damaged insulation. If the wiring is in good condition it should be determined
whether the current reaches the coil. A screwdriver should be rested over the
"Bat" terminal of the coil and at the same time touch some metal part of car
with the end of the screwdriver. If a flash or spark is obtained, the coil is
faulty and a new one should be installed. If no current reaches the coil, the
trouble is due to a loose connection, broken wire, defective switch, dead
battery, or poor ground connection.
To Set Ignition Timing
The breaker points should be adjusted to .020" opening and
the manual spark control lever set in the fully advanced position. The
crankshaft should be rotated until No. 4 piston is going up on exhaust stroke
and stopped when the piston is .050" before top dead center. The bolt which
clamps the distributor timing lever to the distributor should be loosened and
the distributor cap removed to see that the rotor brush is at No. 1 spark plug
cable terminal. The distributor should next be rotated in an anti-clockwise
direction, as viewed from above, until No. 1 cam begins to separate the breaker
points. When doing this the distributor rotor should be pressed against the
direction of rotation to be certain that all backlash is removed. The clamp
screw should then be tightened and the distributor cap reinstalled as well as
the spark plug cables connected to the proper spark plugs and terminals on the
distributor cap. The spark control button on the instrument panel should be
checked for full advance and retard.
Firing Order
The firing order of the cylinders is 1-3-4-2. The wires
from the spark plugs should be connected to the terminals on the distributor
corresponding with the number of the
cylinder in which the spark plugs are placed. Number 1 cylinder is nearest the
radiator. The wiring diagram (Fig. 9) indicates the location of the
distributor terminals for the different spark plugs.
Spark Advance
For all ordinary road driving the spark control button
should be in the advanced position, which is all the way in to the instrument
panel. When pulling hard with a wide open throttle, but not at high vehicle
speed, t he spark should be retarded by pulling the control button about half
way out. When cranking the engine by hand, the spark control button should be
all the way out. The automatic advance will take care of all other conditions.