2-03
Ignition System
2-03
4.
While holding the high tension lead approximately 3/16 inch from
the cylinder head or any other good ground, crank the engine
with an auxiliary starter switch.
If the spark Is good, the trouble lies in the secondary circuit.
If there is no spark or a weak spark, the trouble is in the primary
circuit. coil to distributor high tension lead, or the coil.
Primary Circuit
A breakdown or energy loss in the primary circuit can be caused
by: defective primary wiring. or loose or corroded terminals; burned,
shorted, sticking or improperly adjusted breaker points; a defective
coil; or defective condenser.
A complete test of the primary circuit consists of checking the
circuit from the battery to the coil, the circuit from the coil to ground,
and the starting ignition circuit.
Excessive voltage drop in the primary circuit will reduce the
secondary output of the ignition coil, resulting in hard starting and poor
performance.
To isolate a trouble in the primary circuit, use a voltmeter and
perform the following tests: Battery to Coil, Starting Ignition Circuit,
Resistance Wire, Coil to Ground, or Breaker Points.
Secondary Circuit
A breakdown or energy loss in the secondary circuit can be
caused by: fouled or improperly adjusted spark plugs; defective high
tension wiring; or high tension leakage across the coil, distributor cap
or rotor resulting from an accumulation of dirt.
FIG. 4. Battery-to-Coil and Starting Ignition Circuit Test
To check the spark intensity at the spark plugs, thereby isolating
an ignition problem to a particular cylinder, proceed as follows:
Starting Ignition Circuit Voltmeter Test
1.
Disconnect a spark plug wire. Check the spark intensity of
I.
Connect the voltmeter leads as shown in Figure 4.
one wire at a time.
2.
Disconnect and ground the coil to distributor high tension lead at
2.
Install a terminal adapter in the terminal of the wire to be
the distributor.
checked. Using insulated pliers, hold the adapter approximately
3.
With the ignition ,witch off, crank the engine with an auxiliary
3/16 inch from the exhaust manifold and crank the engine, using
starter switch while observing the voltage drop.
a remote starter switch. The spark should jump the gap
4.
If the voltage drop is 0.4 volt or less, the starting ignition circuit is
regularly.
satisfactory.
3
If the spark intensity of all the wires is satisfactory, the coil,
5.
If the voltage drop is greater than 0.4 volt, clean and tighten the
condenser, rotor, distributor cap and the secondary wires are
terminals in the circuit or replace the wiring as necessary.
probably satisfactory.
If the spark is good at only some wires, check the resistance of
Coil to Ground Voltmeter Test - (Conventional - System)
the faulty leads.
1.
Connect the voltmeter leads as shown in Figure 5.
If the spark is equal at all wires, but weak or intermittent, check the
2.
Close the breaker points.
coil, distributor cap and the coil to distributor high tension wire. The
3. Turn all accessories off.
wire should be clean and bright on the conducting ends, and on the
coil tower and distributor sockets. The wire should fit snugly and be
bottomed in the sockets.
IGNITION SYSTEM TESTS
Battery to Coil Voltmeter Test
1.
Connect the voltmeter leads as shown in Figure 4.
2.
Connect a jumper wire from the distributor terminal of the coil to
a good ground on the distributor housing.
3.
Turn the accessories off.
4.
Turn the ignition switch on.
5.
If the voltmeter reading is between 4.5 and 6.9 volts, the
primary circuit from the battery to the coil is satisfactory.
6.
If the voltmeter reading is greater than 6.9 volts, check
the following:
The battery and cables for loose connections or corrosion
The primary wiring for worn insulation, broken strands, and
loose or corroded terminals
If the voltmeter reading is less than 4.5 volts the ignition
resistor should be replaced.
Check the starter-relay-to-ignition switch for damage.
FIG. 5. Coil to Ground Test
