Ignition System - Hall Effect Dodge Caravan I

DESCRIPTION

Electronic Spark Control system, used on Chrysler Motors FWD vehicles with 2.2L, 2.5L and 3.9L engines, features a Hall Effect distributor and spark control computer.

The heart of the system is the computer. It provides an infinite number of variable advance curves. This allows ignition of lean air/fuel mixtures according to different modes of engine operation.

The computer contains an electronic printed circuit board which receives signals from various engine sensors. An analysis of these signals determines current engine mode and responds by advancing or retarding ignition timing.

The computer determines when the ignition event is required and signals the ignition coil to produce electrical impulses that fire the spark plugs. Computer is located on the fenderwell.

The connection to other fuel/ignition components is by 10-wire and 14-wire connectors. Up to 5 engine sensors feed information to the computer. These include a vacuum transducer, mounted on the computer housing, the distributor mounted Hall Effect pick-up assembly, engine coolant temperature sensor, carburetor switch and oxygen sensor.

The computerized spark control system eliminates need for vacuum or centrifugal advance units. Hall Effect distributor is connected to the computer system by a 3-terminal connector. (Scheme 2) The distributor sends small alternating current signals to the computer as rotor shutter blades enter and leave the gap in the Hall Effect switching unit pick-up assembly.

Carburetor switch senses when engine is at idle. Coolant temperature switch or sensor keeps the computer informed on engine operating temperature. Vacuum transducer informs the computer of engine vacuum (load).

Scheme 1

Scheme 2

OPERATION

The computer has 2 functional modes, start and run. Start mode functions only during engine cranking and starting. Fixed amount of spark advance is provided, based on distributor position.

Run mode functions only when engine starts and is operating normally. Hall Effect pick-up assembly and 4 sensors provide information to computer, which varies spark advance to match engine operating conditions. Spark timing and dwell cannot be adjusted in start mode.

Engine sensors work together. If engine temperature drops below a predetermined level, coolant temperature switch signals the computer to prevent additional ignition advance from the vacuum transducer signal. As coolant temperature increases, vacuum increases and additional ignition advance is called for.

For maximum ignition advance, the carburetor switch must remain open. During the time when advance will not occur quickly, vacuum advance is controlled by engine RPM and will build up at a slow rate. If carburetor switch closes, build-up of advance will be cancelled.

Hall Effect pick-up signal is a reference, based on sensor input, providing maximum ignition advance. The ignition event occurs when computer shuts off current to the ignition coil primary circuit. As the magnetic field collapses, a high voltage surge occurs in the secondary, firing the appropriate spark plug.

If computer run mode fails, system will go into start mode. This enables the vehicle to be driven in for repair. Performance and fuel economy will be poor while operating in start mode. If the Hall Effect pick-up or start mode of the computer fails, engine will not start or run.

ADJUSTMENTS

No adjustments can be made to the Hall Effect pick-up unit. Dwell and spark timing cannot be adjusted in run mode. Initial fixed timing (start mode) can be adjusted by changing distributor position.

IGNITION SYSTEM STARTING TEST

1. Remove coil secondary wire from distributor center tower. Hold end of wire about 1/4" from a good engine ground. Crank engine and check for spark. If there is spark, slowly move coil secondary wire away from ground while cranking engine. Check for arcing at coil tower. If arcing occurs, replace ignition coil.
2. If spark is weak, inconsistent or there is no spark, proceed to FAILURE TO START TEST. If spark is good and there is no arcing at coil tower, check distributor cap, rotor, spark plug wires and spark plugs. If components are okay, ignition system is working properly and is not cause of no start condition. Check fuel system and engine mechanical condition.

FAILURE TO START TEST

Scheme 3

1. Remove coil secondary wire from distributor cap and position it 1/4" away from good engine ground. Turn ignition on. Using special jumper wire, intermittently ground coil negative terminal. Watch for spark at coil wire. (Scheme 3)
2. If there is spark, proceed to step 5). If there is no spark, turn ignition off. Disconnect 10-wire connector from spark control computer. Turn ignition on. Using special jumper wire, intermittently ground coil negative terminal. Watch for spark at coil wire.
3. If there is spark, replace spark control computer. Check if engine will start. If there is no spark, measure voltage at coil positive terminal. Voltage should be within one volt of battery voltage. If there is no voltage, check and repair wiring between battery and coil positive terminal.
4. If there is voltage at coil positive terminal, measure voltage at coil negative terminal. Voltage should be within one volt of battery voltage. If there is voltage, but no spark when grounding coil negative terminal, replace ignition coil. If there is no voltage, replace ignition coil.
5. If there is voltage but engine will not start, hold carburetor switch open with a thin cardboard insulator. Measure voltage at carburetor switch. Voltage should be within one volt of battery voltage. If there is voltage, proceed to step 9).
6. If there is no voltage, turn ignition off. Disconnect computer 10-wire connector. Turn ignition on. Measure voltage at connector cavity "2". Voltage should be within one volt of battery voltage. If there is no voltage, turn ignition off. Check for continuity in wiring between connector cavity "2" and battery. Repair wiring as necessary.
7. If there is voltage, turn ignition off. Check for continuity between connector cavity "7" and carburetor switch. If there is no continuity, check for open circuit in wiring between carburetor switch and connector cavity "7". If there is continuity, check for continuity between connector cavity "10" and ground.
8. If there is continuity, replace defective computer. Repeat step 5). If there is no continuity, check for open circuit in wiring. If wiring is okay, but engine still will not start, proceed to step 9).
9. Reconnect computer 10-wire connector. Disconnect distributor harness connector. Connect distributor harness connector terminals "2" and "3" using a jumper wire. Turn ignition on. Hold coil secondary wire near a good engine ground.
10. Make and break connection at either end of jumper wire several times. There should be a spark at coil wire. If there is spark at coil wire, but engine still will not start, replace Hall Effect pick-up.
11. If there is no spark at coil wire, measure voltage at harness connector terminal "1". Voltage should be within one volt of battery voltage. If voltage is as specified, turn ignition off. Disconnect computer 10-wire connector.
12. Check for continuity between 10-wire connector cavity "9" and distributor harness connector terminal "2". Check for continuity between 10-wire connector cavity "5" and distributor harness connector terminal "3". If there is no continuity performing these checks, repair wiring harness. If there is continuity, replace computer. Repeat steps 9) and 10).
13. If there was no voltage in step 11), turn ignition off. Disconnect computer 10-wire connector. Check for continuity between connector cavity "3" and distributor harness connector terminal "1". If there is no continuity, repair wire and repeat steps 9) and 10).
14. If there is continuity, turn ignition on. Check for battery voltage between 10-wire connector cavities "2" and "10". If battery voltage is present, replace defective computer. Repeat steps
15. and 10). If battery voltage is not present, computer is not grounded. Check ground wire and repeat steps 9) and 10).

Basic Timing

Check and adjust initial timing before testing for poor performance.

Carburetor Switch

Note. Grounding carburetor switch on most systems with feedback carburetor gives a fixed air/fuel ratio.

Turn ignition off. Disconnect computer 10-wire connector. With throttle completely closed, check continuity between connector cavity "7" and ground. If there is no continuity, check wire and carburetor switch. Open throttle. Check continuity between computer 10-wire connector cavity "7" and ground. There should be NO continuity with throttle open.

Coolant Sensor

Turn ignition off. Disconnect coolant sensor connector. Connect ohmmeter to coolant sensor terminals. With coolant temperature about 70°F (21°C), sensor resistance should be 5000-6000 ohms. With coolant temperature at 200°F (93°C), sensor resistance should be 700-800 ohms.

Throttle Control System Test

1. Connect tachometer to engine. Start engine and run until normal operating temperature is reached. Depress and release accelerator pedal. A higher than idle speed should be obtained. Turning A/C on should produce a slight decrease in idle speed. Turning A/C off should return idle speed to normal.
2. With A/C on, compressor clutch should cycle on and off, and solenoid kicker plunger should extend and retract. If plunger does not move when compressor clutch cycles or after starting engine, check solenoid kicker system for vacuum leaks.
3. If engine speed does not increase, turn ignition off. Disconnect carburetor 6-wire connector. Check solenoid resistance using an ohmmeter connected to Black wire and ground. Resistance should be 20-100 ohms. If not, replace solenoid.
4. Start vehicle. Before time delay runs out, measure voltage between vacuum solenoid terminals. Voltage reading should be within 2 volts of charging system voltage. If voltage is not as specified, replace computer. Turning A/C on, should produce charging system voltage after time delay has run out. If not, check wiring back to instrument panel for an open circuit.

Scheme 4

1. Disconnect pick-up coil leads at wiring harness connector. Remove pick-up coil lead connector from retainer. Remove splash shield retaining screws. Remove splash shield. Remove distributor cap and wires as an assembly.
2. Rotate crankshaft until rotor is pointing toward cylinder block. Scribe a mark on block to indicate rotor position for reassembly reference. Remove distributor. NOTE: When removing spark plug wires from distributor cap, do not pull on wires. Positive-locking wires must be released from inside cap. (Scheme 4)
3. Remove rotor. Remove Hall Effect pick-up assembly. Mark drive gear (or distributor drive) position on distributor shaft. Using a pin punch, drive roll pin from shaft. NOTE: Hall Effect pick-up assembly may be replaced without removing distributor from engine.
4. Remove drive gear (or distributor drive) and remove shaft from housing. Remove thrust washers, nylon spacers and block seals (if equipped).

REASSEMBLY

To reassemble, reverse disassembly procedure. Correct rotor has "ESA" stamped on its top. Check rotor for proper grounding of shutter blades.