Ignition System - Dura-Spark Ii Ford Cab & Chassis Ranger

DESCRIPTION

Dura-Spark II is a solid-state ignition system, consisting of a breakerless distributor, electronic control module, ignition coil, battery, ignition switch, secondary wires and various wiring harnesses. (Scheme 1)and (Scheme 3).

Most models use a large rotor, a distributor cap and adapter, secondary wires, and wide gap spark plugs to take advantage of higher energy produced in the Dura-Spark II ignition system. The Dura-Spark II system can be identified by the module's 2-wire and 4-wire connectors. (Scheme 1)and (Scheme 2). Depending on calibration, some models use the Universal Ignition Module (UIM). This module has three connectors.

OPERATION

As the engine cranks, the distributor shaft turns. A reluctor (armature) on the distributor shaft rotates past a pick-up coil (stator).

The reluctor has the same number of teeth as the engine has cylinders. As the teeth rotate past the pick-up coil, a signal is sent to the electronic control module.

Based on this signal, the module then determines when to turn current off and on in the primary windings of the ignition coil. This current collapse in the primary, causes a high voltage surge in the secondary.

This high voltage is routed to the spark plugs through the rotor, distributor cap and spark plug wires. A discussion of system components follows.

Dura-Spark II Ignition System Wiring Diagram Electronic control module has a 2-wire and 4-wire connector. Scheme 1

ELECTRONIC CONTROL MODULE

Each Dura-Spark II module has 6 wires (a 2-wire and a 4-wire connector). (Scheme 1)and (Scheme 2). The Red and White wires are the ignition feed wires. The White wire is for cranking, and the Red wire is for operation after the engine is running.

The Red wire circuit contains a 1.1 ohm resistance wire. The current to the primary circuit of the ignition coil is turned off and on through the Green wire.

The Orange and Purple wires transmit signals to the electronic control module from the reluctor (armature) and pick-up coil (stator) in the distributor.

The Black wire is used to ground the electronic control module through the distributor housing.

Electronic control modules of the UIM type, having the third connector, provide for additional spark timing control. This connector receives a signal from the Ignition Barometric Switch, Ignition Timing Vacuum Switch, or the MCU module depending on engine calibration.

DISTRIBUTOR

Distributors on 6-cylinder models rotate clockwise, those of V8 models, counterclockwise.

A reluctor, containing the same number of teeth as the engine has cylinders, turns with the distributor shaft. The pick-up coil contains a permanent magnet, causing a magnetic field around the pick-up coil.

As the teeth of the reluctor approach and pass the pick-up coil, the magnetic field builds and collapses. This causes a signal to be sent to the electronic control module.

In turn, the control module turns the ignition coil primary off and on, causing a high voltage surge in the secondary.

Control Module & Distributor Connectors for Dura-Spark II System Compare terminal location to shape. Scheme 2

Dura-Spark II systems have an adapter between the distributor housing and cap. (Scheme 3) Distributor caps are larger than for conventional distributors, and have male terminals. Dura-Spark II distributors have both centrifugal and vacuum advance mechanisms.

On single diaphragm vacuum units, increased vacuum causes the movable pick-up coil to pivot on the lower plate assembly, advancing spark timing.

On dual diaphragm units, the outer (primary) diaphragm operates from carburetor vacuum to provide timing advance during normal idle off driving conditions. It is connected to the pick-up coil assembly.

The inner (secondary) diaphragm operates from intake manifold vacuum and acts to retard ignition timing. The inner diaphragm is connected to the outer diaphragm rod by means of sliding linkage. Stronger intake manifold vacuum can override carburetor vacuum during closed throttle operation, retarding spark timing.

IGNITION COIL

Coils are oil-filled, and are energized whenever the ignition switch is in the "ON" or "START" position. They contain a positive "BATT" terminal, a negative "TACH" (sometimes called "DEC") terminal, and a single secondary terminal.

Note. "DEC" refers to Distributor Electronic Control. This terminal is also referred to as the "Tach Test" terminal.

A special connector attaches the Green wire from the control module to the negative terminal ("TACH") and the wire from the ignition switch to the positive terminal ("BATT").

Schematic of Dura-Spark II Ignition System Illustration shows relationship of components to each other. Scheme 3

RESISTANCE WIRE

The special ignition resistance wire in the Red wire circuit must be of specified length and diameter to reduce operating voltage.

When new wire is installed, old wire should be removed from system. Resistance value of wire is 1.0-1.1 ohms.

SYSTEM PROTECTION

Dura-Spark systems are protected against electrical currents produced or used by any other vehicle component during normal operation. However, damage to the ignition system can occur if proper testing procedures are not followed.

DURA-SPARK II SYSTEM PRECAUTIONS

Since the electronic control module and ignition coil are "ON" whenever the ignition switch is in the "ON" or "START" position, the system will generate a spark whenever the ignition switch is turned "OFF". This feature may be used as a diagnostic tool to check for continuity of circuit, coil and ignition switch. Some testing precautions follow

Note. Silicone dielectric grease must be applied to all insulating areas at distributor (not on cap or rotor, if vehicle is equipped with FM radio), coil and spark plug boots.

Note. A 3/4" clearance must be maintained at distributor cap mounting edge, spark plug wire terminals, and coil tower to prevent high voltage arc to ground.

Note. When replacing spark plug wires, insure wire made of the same material is used for a replacement. Silicone/Silicone wire can be identified by the letters "SS" appearing on the wire in WHITE lettering. Silicone/EPDM wire can be identified by the letters "SE" appearing on the wire in BLACK lettering. The "SS" wire is used on cylinders subject to very high engine temperatures.

Note. When removing distributor cap and adapter, always remove the distributor cap first, then the adapter.

ADJUSTMENTS

No adjustments are to be made to the ignition system except initial engine timing and spark plug gap.

TESTING

Note. All wire colors shown refer to colors of electronic control module wires. For example, "the Green wire leading to the coil" would refer to any colored wire leading to the coil, that connects to the module's Green wire. Therefore, when making tests, wires must be traced back to control module for proper color identification. Also, when a test is completed and a problem is found, make the necessary repair and repeat the failed test to be sure that the problem has been corrected.

When checking the secondary voltage, do not remove the following spark plug wires while the engine is running or cranking

1. Plug No. 1 or 8 on V8 engines.
2. Plug No. 3 or 5 on 6 cylinder engines.
3. Plug No. 1 or 3 on 4 cylinder engines.

IGNITION SPARK TESTER

Either use an ignition spark tester, or modify a spark plug for use in testing ignition system. To modify plug, cut off side terminal, and install spring clip for grounding plug housing. (Scheme 4)

Modified Spark Plug and Spark Tester Testers may be purchased from most tool suppliers. Scheme 4

START CIRCUIT CHECK

1. Connect spark tester or modified spark plug between ignition coil wire and a good engine ground. Crank engine with ignition switch. If no sparks occur at tester gap, proceed to step 2). If sparks occur at tester gap, proceed to RUN CIRCUIT CHECK.
2. If no sparks occurred in step 1), remove coil wire from distributor cap and ignition coil. Connect ohmmeter leads to both ends of coil wire, and measure resistance.
3. If resistance is more than 5,000 ohms per inch, replace coil wire. Also, inspect ignition coil for damage or carbon tracking. Crank engine to verify distributor rotation and proceed to «VOLTAGE SUPPLY CIRCUITS CHECK»(/ford/cab-chassis-ranger/1985-1986/remont/ignition-system/#ignition-system-dura-spark-ii) .

RUN CIRCUIT CHECK

1. Remove ignition coil wire from distributor cap, and install spark tester on wire. Turn ignition switch from "OFF" to "RUN" to "OFF" several times.
2. Sparks should occur at tester gap each time switch goes from "RUN" to "OFF" position. Remove spark tester and reconnect coil wire to distributor cap.
3. If sparks occur, check distributor cap, adapter, and rotor for cracks, carbon tracking or lack of silicone compound. Also check for roll pin retaining reluctor to sleeve in distributor shaft and check that Orange and Purple wires are not crossed between distributor and control module.
4. If no sparks occurred in step 1), proceed to CONTROL MODULE VOLTAGE CHECK.

Scheme 5

1. With ignition switch "OFF", carefully insert small straight pin in Red module wire. (Scheme 5) DO NOT allow straight pin to touch ground. Measure battery voltage at battery. Attach negative voltmeter lead to distributor base and positive lead to straight pin. (Scheme 5): Checking Control Module "RUN" & "START" Ckts with Voltmeter Do not let straight pin touch a ground.
2. Turn ignition switch to "RUN" position. Measure voltage at straight pin in Red wire. After reading voltmeter, turn ignition switch "OFF" and remove straight pin.
3. Voltage at pin should read at least 90 percent of battery voltage. If so, proceed to «BALLAST RESISTOR CHECK»(/ford/cab-chassis-ranger/1985-1986/remont/ignition-system/#ignition-system-dura-spark-ii__ballast-resistor-check).
4. If reading was less than 90 percent of battery voltage, check wiring harness between control module and ignition switch. Also check for a worn or damaged ignition switch.

BALLAST RESISTOR CHECK

1. Disconnect control module 2-wire connector and remove coil connector from coil. Connect ohmmeter leads to "BATT" terminal of coil connector and to harness connector terminal mating with Red control module wire. Read ohmmeter, then reconnect all connectors.
2. If resistance is 0.8-1.6 ohms, problem is either intermittent or not in ignition system. If resistance was less than 0.8 or more than 1.6 ohms, replace resistance wire.

Scheme 6

1. If starter relay has an "I" terminal, disconnect cable between relay and starter motor at starter relay. If starter relay does not have an "I" terminal, disconnect wire to "S" terminal of starter relay. Insert small straight pins in Red and White control module wires. CAUTION: DO NOT allow straight pins to contact an electrical ground.
2. Measure battery voltage at battery. Connect negative voltmeter lead to distributor base, and note voltmeter reading in each of the following situations: Positive voltmeter lead connected to pin in Red wire, with ignition switch in "RUN" position. Positive voltmeter lead connected to pin in White wire, with ignition switch in "START" position. Positive voltmeter lead connected to "BATT" terminal of ignition coil, with ignition switch in "START" position. (Scheme 6) (Scheme 6): Checking for Battery Voltage at Ignition Coil Positive ("BATT") Terminal
3. Turn ignition switch off. Reconnect any wires disconnected from starter relay. Remove voltmeter leads, and remove straight pins from wires.
4. If voltage readings were at least 90 percent of battery voltage, test result is okay, proceed to IGNITION COIL VOLTAGE SUPPLY CHECK. If reading was less than 90 percent of battery voltage, check for faulty wiring harness connectors or damaged ignition switch.

IGNITION COIL VOLTAGE SUPPLY CHECK

1. Connect negative lead of voltmeter to distributor base and positive lead to "BATT" terminal of ignition coil. (Scheme 6) Turn ignition switch to "RUN" position, and read voltmeter. Turn ignition switch "OFF".
2. If voltage was 6-8 volts, proceed to PICK-UP COIL & DISTRIBUTOR WIRING HARNESS CHECK. If voltage was less than 6 volts or more than 8 volts, proceed to IGNITION COIL PRIMARY RESISTANCE CHECK

PICK-UP COIL & DISTRIBUTOR WIRING HARNESS CHECK

1. Disconnect control module 4-wire connector, and inspect for dirt, corrosion or damage. Connect ohmmeter leads to harness connector terminals that mate with Orange and Purple control module wires.
2. Resistance should be 400-1300 ohms. If so, proceed to CONTROL MODULE TO DISTRIBUTOR WIRING HARNESS CHECK. If resistance is not to specifications, proceed to «PICK-UP COIL RESISTANCE CHECK»(/ford/cab-chassis-ranger/1985-1986/remont/ignition-system/#ignition-system-dura-spark-ii__pick-up-coil-resistance-check) .

CONTROL MODULE TO DISTRIBUTOR WIRING HARNESS CHECK

1. Disconnect 4-wire control module connector. Connect an ohmmeter lead to distributor base. Alternately, connect the other ohmmeter lead to wiring harness connector terminals that mate with Orange and Purple wires of control module connector.
2. If resistance is greater than 70,000 ohms, test result is OK. Proceed to IGNITION COIL SECONDARY RESISTANCE CHECK. If resistance was less than 70,000 ohms, check wiring harness between control module connector and distributor, including distributor grommet.

IGNITION COIL SECONDARY RESISTANCE CHECK

1. Disconnect ignition coil secondary wire and ignition coil connector from coil. Connect ohmmeter leads to ignition coil "BATT" terminal and to high voltage terminal. Measure resistance and reconnect wire and connector.
2. If resistance is 7700-10,500 ohms, coil is OK, proceed to MODULE-TO-COIL WIRE CHECK. If resistance is less than 7700 or greater than 10,500 ohms, replace ignition coil.

MODULE-TO-COIL WIRE CHECK

1. Disconnect control module 4-wire connector and ignition coil connector. Connect one ohmmeter lead to distributor base and the other to "TACH" terminal of ignition coil connector.
2. Measure resistance. There should be no continuity between wire and ground. If continuity exists, check wiring harness for short circuit.
3. Disconnect ohmmeter lead from distributor base. Connect meter to harness connector terminal that mates with Green wire and measure resistance. If wire shows any resistance, check wiring harness.

PICK-UP COIL RESISTANCE CHECK

1. Disconnect distributor connector from wiring harness. Connect ohmmeter leads to distributor connector terminals that mate with Orange and Purple wires of control module. Measure resistance of pick-up coil. Reconnect distributor connector to wiring harness.
2. Resistance should be 400-1000 ohms. If resistance is within this range, pick-up coil is OK. If resistance is not within specified range, replace pick-up coil assembly.

IGNITION COIL PRIMARY RESISTANCE CHECK

1. Disconnect ignition coil connector. Connect ohmmeter leads to "BATT" and "TACH" terminals of ignition coil. Measure resistance, and reconnect ignition coil connector.
2. If resistance is 0.8-1.6 ohms, coil is OK. Proceed to PRIMARY CIRCUIT CONTINUITY CHECK. If resistance is less than 0.8 or greater than 1.6 ohms, replace ignition coil.

PRIMARY CIRCUIT CONTINUITY CHECK

1. Insert a small straight pin in control module Green wire. Connect negative voltmeter lead to distributor base, and positive lead to pin in Green wire.
2. With ignition switch in "RUN" position, measure voltage. Turn ignition switch "OFF" and remove straight pin from Green wire.
3. If voltage reading was greater than 1.5 volts, proceed to GROUND CIRCUIT CONTINUITY CHECK. If voltage reading was 1.5 volts or less, inspect wiring between module and coil.

GROUND CIRCUIT CONTINUITY CHECK

1. Insert a small straight pin in control module Black wire. Connect negative lead of voltmeter to distributor base, and positive lead to straight pin in Black wire. With ignition switch in "RUN" position, measure voltage. Turn ignition switch "OFF", and remove straight pin.
2. If voltage reading was greater than 0.5 volt, proceed to DISTRIBUTOR GROUND CIRCUIT CONTINUITY CHECK. If voltage was 0.5 volt or less, replace control module.

DISTRIBUTOR GROUND CIRCUIT CONTINUITY CHECK

1. Disconnect distributor connector from wiring harness. Connect ohmmeter leads to distributor base, and to Black wire terminal in distributor connector. Measure resistance, then reconnect distributor connector to wiring harness.
2. If resistance was less than 1 ohm, circuit is OK. If resistance was greater than 1 ohm, check ground screw in distributor housing.

SPARK PLUG WIRE RESISTANCE CHECK

1. Remove distributor cap, and disconnect spark plug end of suspected wire or wires. Connect ohmmeter leads to spark plug terminal and terminal inside distributor cap (each end of wire). CAUTION: Never puncture a spark plug wire when measuring resistance.
2. If resistance is less than 5000 ohms per inch, visually inspect wires for damage and remove spark plug for inspection and/or replacement. If resistance is greater than 5000 ohms per inch, disconnect suspected wire from distributor cap and again connect leads to each end of wire.
3. If resistance is now less than 5000 ohms per inch, inspect distributor cap and spark plug wire terminals for damage. Repair as necessary. If resistance is still greater than 5000 ohms per inch, replace wire(s).

DISASSEMBLY

1. Remove distributor cap, adapter, and rotor. Disconnect distributor wiring harness plug. Using a small gear puller or two screwdrivers, carefully pry armature from sleeve and plate assembly. Remove roll pin. CAUTION: DO NOT pinch stator wires when removing armature.
2. On V8 engines, remove large wire retaining clip from base plate annular groove. Remove ground screw base, and pull up to remove rubber grommet from base.
3. Remove "E" clip securing diaphragm rod advance link to stator assembly. Lift diaphragm rod off post on stator assembly, and move it out against housing. Remove stator assembly.
4. On 6-cylinder models, remove "E" clip washer and wave washer, securing stator assembly to lower plate. Remove stator assembly ground screw and lift assembly from distributor.

REASSEMBLY

Reverse disassembly procedure. Using new roll pin, install roll pin in different groove, 180° from original groove.

Components of Dura-Spark II Distributor Reluctor shown, having 8 teeth, is for V8 engine. Scheme 7

See also:
• VOLTAGE SUPPLY CIRCUITS CHECK
• BALLAST RESISTOR CHECK
• PICK-UP COIL RESISTANCE CHECK