DUAL MODE TIMING IGNITION MODULE
See Figures 1 and 2
On some applications, a special Dura Spark II ignition module is used with altitude compensation. This special module plus the barometric pressure switch, allows the base engine timing to be modified to suit altitude conditions. All other elements and performance characteristics of this module are identical in both modes of operation to the basic Dura Spark II system. All Dura Spark II modules equipped with altitude features, have three connectors instead of the normal two. A barometric switch provides an automatic retard signal to the module at different altitudes, giving appropriate advanced timing at higher altitude and retard mode for spark knock control at lower altitudes.
See Figure 3
All systems consist of a primary (low voltage) and secondary (high voltage) circuit.The Primary Circuit:
The components involved in the primary circuit are:
- Ignition switch
- Integral primary circuit resistance wire
- Primary windings of the ignition coil
- Magnetic pickup coil assembly in the distributor
- Ignition module
The components of the secondary circuit are:
- Secondary windings of the ignition coil
- Distributor rotor
- Distributor cap and adapter
- Secondary spark plug wires
- Spark plugs
With the ignition switch in the ON position, the primary circuit is energized and the magnetic field is built up by the current flowing through the primary windings of the ignition coil. When the armature spokes align with the center of the magnetic pickup coil, the module turns off the coil primary current and the high voltage is produced in the secondary circuit by the collapsing magnetic field. High voltage is produced each time the magnetic field is caused to collapse due to a timing circuit in the module, which starts and stops the primary circuit through the coil. The high voltage flows through the coil secondary lead to the distributor cap, where the rotor distributes the spark to the proper spark plug terminal in the distributor cap. The secondary current then flows through the secondary wire to the spark plug.
No adjustments are made to the Dura Spark II ignition system except the initial timing and spark plug gap.
SECONDARY WIRE USAGE
See Figure 4
Spark plug wires that are used with the Dura Spark II system are 8mm in size, to contain the higher output voltage. Two types of wires are used in this system and some engines will have both types. It is important to identify the type of wire to a cylinder before a replacement is obtained and installed. Both types are blue in color and have silicone jacketing. The insulation material underneath the jacketing can be a EPDM or have another silicone layer, separated by glass braid. EPDM wires are used where the engine temperatures are cooler and are identified by the letters SE . The silicone jacket type are used where the engine temperatures are high and are identified by the letters SS .
Whenever a Dura Spark II high tension wire is removed for any purpose from a spark plug, coil or distributor cap, silicone grease must be applied to the boot before it is reconnected.
The spark plug wires are marked with the cylinder number, model year and date of cable manufacture (quarter and year). Service replacement wires do not have this information.
To properly diagnose the ignition system, a starting place must be established and an order of inspection followed until the fault is found and repaired. A recheck should be made, again in its order of inspection, to verify the repairs and to assure trouble-free operation.Run Mode Test
- If no spark is available at the spark plug, remove the coil high tension lead at the distributor and either place it 1/4 in. from the engine block or place a modified spark plug into the coil wire and ground the spark plug body.
- Turn the ignition switch to the RUN position and tap the distributor body with a screwdriver type tool handle. Check for spark while tapping.
- If spark is available, crank the engine with the starter and check for spark. If spark occurs, the primary ignition system is OK.
- If no spark occurs, turn the key to the OFF position and crank the engine to align the engine timing pointer with the initial timing degree line on the damper pulley. Turn the key to the RUN position and again tap the distributor and check for spark.
- If no spark occurs, measure battery voltage and measure the battery voltage on the module/s red wire without disconnecting any connectors. The voltage in the red wire should equal battery voltage.
- If battery voltage is not present in the module red wire, repair the circuit between the battery and the module connector. Recheck the voltage supply.
- With the voltage present in the module&rsquos red wire, cycle the ignition switch between the RUN and OFF position. A spark should be seen each time the switch is turned to the OFF position.
If no spark occurs, measure the voltage on the battery side of the coil.
- Less than 6 volts - Repair the wire carrying current to the battery terminal of the coil and repeat test.
- If voltage is 6-8 volts - Substitute, but do not install, a known good module and repeat the test. If spark then occurs, reconnect the original module to verify its being defective. Replace as required. Refer to step 10 if the battery voltage is present.
If a spark occurs from step 7, substitute, but do not install, and ground a good distributor of any calibration 4-, 6- or 8-cylinder. Spin the distributor shaft and check for high tension spark.
- If a spark occurs, reconnect the old distributor and verify its being defective. Replace as required.
- If no spark occurs, disconnect the distributor connector and 4 post connector at the module. Check the harness wires that mate with the module and distributor orange and purple wires for continuity between the module and distributor end of the harness. Check to be sure there is no short between the two wires and there is an open circuit to ground. If not OK, repair the wiring and repeat the test to verify repairs.
- If no spark occurs after completing step 9b, reconnect the distributor connector and substitute, but do not install, a known good module and repeat the test. If a spark occurs, reconnect the original module and verify it is defective. Repair as required.
If battery voltage is present at the terminal of the coil:
- Disconnect the 4 wire connector at the module. Insert a paper clip between the green and black wires of the module and remeasure the voltage at the battery terminal of the coil.
- If the voltage is between 6 to 8 volts, substitute, but do not install, a known good module and repeat the tests. If spark occurs, reconnect the old module and verify its being defective. Replace as required.
- If battery voltage is still present at the battery terminal of the coil, be sure the coil connector remains in place on the coil and ground the negative terminal of the coil. Remeasure the voltage on the coil battery terminal. If battery voltage still is present, remove the paper clip from the 4 wire connector and reconnect the module. Substitute, but do not install, a known good coil and repeat the test. If a spark does not occur, connect the original coil and substitute; a known good module, but do not install, and repeat the test. If a spark occurs, replace the module as required. If 4 to 7 volts is measured at the coil positive terminal, remove the ground from the coil negative terminal and ground from the paper clip connector in the 4 wire connector. Remeasure the voltage at the coil battery terminal. The voltage should be 4 to 7 volts. If the 4 to 7 volts are present, repair the ground circuit mating with the module black wire. Remove the paper clip from the 4 wire connector and reconnect the module. Repeat the test. If no voltage is present, repair the module to coil wire that mates with the module green wire. Remove the paper clip from the connector and reconnect the module. Repeat the test.
- Measure the voltage at the battery terminal of the ignition coil while cranking the engine. The reading should be within 1.0 volt of battery voltage. If not with-in specifications, repair the wire or circuit to the coil terminal.
- While cranking the engine, check for spark from the high tension leads.
- If no spark occurs, check the battery voltage on the white wire, while cranking the engine without disconnecting the module's two wire connectors. The voltage should be within 1.0 volt of battery voltage. If not, repair the white feed wire to the module.
- Substitute, but do not install, a known good module and repeat the test. If a spark occurs, reconnect the original module and verify its being defective. Replace as required.
INTERMITTENT OPERATION DIAGNOSIS
Should the ignition system become operative during the tests and a repair has not been made to the system, it is likely an intermittent connection or component has become functional. Try to duplicate the problem with the engine running, by wiggling the wires at the coil, module, distributor and other harness connections, preferably the connections that have been disturbed during the test proceedings. Check all ground connections, especially within the distributor. Disconnecting and connecting connectors may also help.Heating Components for Tests
Using a 250 watt heat lamp, approximately 1-2 in. from the pick-up coil, apply heat for 4 to 6 minutes while monitoring the pick-up coil continuity between the parallel blades of the disconnected distributor connector. The resistance should be 400 to 1000 ohms. Tapping with a screwdriver type handle may also be helpful to locate problem. If specifications cannot be met or held, replace the pick-up coil.IGNITION MODULE
With the engine running, heat the module by placing a 250 watt heat lamp bulb approximately 1-2 in. from the module top surface.
Tapping the module may be helpful, but do not tap hard enough to damage or distort the housing. If this procedure results in an ignition malfunction, substitute, but do not install, a known good module. If the ignition malfunction is corrected by the substitution, reinstall the original module and recheck. Replace the module as required.