The Distributorless Ignition System (DIS) eliminates the conventional distributor and all its components by using multiple ignition coils. On Mustangs equipped with the 2.3L dual-plug DIS ignition system, two coil packs (left and right) are used. Two coil packs are required, since each cylinder is equipped with two plugs. The right coil pack operates continuously; however, the left coil pack may be switched on or off by the EEC-IV processor.
In the DIS system, each coil fires two spark plugs at the same time. The plugs are paired so that the plug on the compression stroke fires, while the other plug is on its exhaust stroke. The next time the coil is fired, the plug that was on the exhaust will be on the compression stroke and the first one will be on exhaust. The spark in the exhaust cylinder is wasted, but little of the coil energy is lost.
The DIS system includes these components:
The 2.3L engine uses a dual-Hall crankshaft sensor, containing two Hall-effect devices (PIP and CID). The Profile Ignition Pickup (PIP) cup has two teeth which generate two positive edges for each crankshaft rotation. The PIP signal provides base spark timing information. The Cylinder Identification (CID) cup has one tooth which generates one positive edge during each crankshaft revolution. The CID is used by the DIS module to determine which coil should be fired. Despite the EEC-IV processor telling the DIS module when to fire, it's the job of the DIS module to decide which coils to fire based on the CID signal. The CID signal is also used by the EEC processor to know which bank of injectors to fire.
In the DIS system, the EEC-IV processor determines the spark angle using the PIP signal to establish base timing. Spark Output (SPOUT) is provided by the EEC-IV processor to the DIS module and serves two purposes. The leading edge fires the coil and the trailing edge controls the dwell time. This feature is referred to as Computer Controlled Dwell (CCD)
The DIS module incorporates an Ignition Diagnostics Monitor (IDM). This is an output signal that provides diagnostic information concerning the ignition system to the EEC-IV processor for self-test. It is also the input signal for the vehicle's tachometer.
If the CID circuit fails and an attempt to start the engine is made, the DIS module will randomly select one of the coils to fire. If hard starting results, turning the key OFF and trying to restart will result in another guess. Several attempts may be needed until the proper coil is selected, allowing the vehicle to be started and driven until repairs can be made. The Failure Effects Mode Management (FMEM) system will try to keep the vehicle drivable despite certain EEC-IV system failures that prevent the processor from providing spark angle or dwell commands. The EEC-IV processor opens the SPOUT line and the DIS module fires the coils directly from the PIP input. This condition will result in a fixed spark angle of 10° and a fixed dwell.2.3L Engine
The DIS ignition module receives the PIP and the CID signals from the crankshaft timing sensor and the SPOUT (Spark Out) signal from the EEC-IV control module. During normal operation, the PIP signal is passed onto the EEC-IV control module and provides base timing and rpm information. The CID signal provides the DIS module with information required to switch between the coils for cylinders Nos. 1 and 4 and the coils for cylinders Nos. 2 and 3. DPI allows the EEC-IV processor to switch the ignition system from single to dual plug operation.
When the window of the cup is in the air gap between the permanent magnet and Hall-effect device, a magnetic flux field is completed. At this time, the magnetic field is allowed to travel from the permanent magnet through the Hall-effect device and back to the magnet. This condition creates a low (0 volts) output signal. As the crankshaft rotates and the tooth on the cup moves into the air gap, the magnetic field will be shunted through the tooth and back to the magnet. During this time, the output signal will change from low to high (source volts).
See Figure 1
The dual Hall crankshaft sensor on the 2.3L engine contains two Hall-effect devices, PIP and CID. The sensor is mounted on a bracket near the crankshaft damper.Ignition Coil Pack
The ignition coil pack contains two separate coils. Each ignition coil fires two spark plugs simultaneously. The spark plug fired on the exhaust stroke uses very little of the ignition coil's stored energy.DIS Ignition Module
The DIS ignition module receives the PIP signal from the crankshaft sensor. The CID signal provides the DIS ignition module with the information required to synchronize the ignition coils so that they are fired in the proper sequence.