Contactless ignition systems with distributor
The 1.5 l, 1.8 l 1993-1996, 2.0 l SOHC, 2.4 l SOHC 1994-1998, 3.0 l SOHC and 3.5 l models are equipped with a contactless ignition system. The ignition timing in such systems is controlled by a special electronic unit (ECU). On the 1.5 l, 1.8 l, 2.4 l and 3.5 l models, the ignition coil and key transistor are built into the distributor housing, on the 2.0 l SOHC and 3.0 l SOHC models, these elements are installed separately.
When the ignition is turned on, battery voltage is supplied to the primary winding of the ignition coil. When the distributor shaft rotates, signal pulses from the on-board processor (PCM) are transmitted to the key transistor of the ignition system, which leads to a periodic short circuit of the negative terminal of the primary winding of the coil (via the transistor) to ground. As a result of such interruptions, high-voltage voltage is induced in the secondary circuit of the coil, transmitted to the spark plugs of the corresponding cylinders and ensuring timely ignition of the air-fuel mixture in them.
Direct Ignition System (DIS)
This type of ignition system is used on models 1.6 l, 1.8 l 1997÷2000, 2.0 l DOHC, 2.4 l SOHC since 1999, 2.4 l DOHC and 3.0 l DOHC. Ignition timing is controlled here, as before, by the ECU or on-board processor (PCM).
The system includes a crankshaft position (CKP) sensor, which signals the control module to monitor the current position of the pistons. By analyzing the information coming from the CKP sensor, the ECU/PCM determines the current engine speed and controls the injection and ignition of the air-fuel mixture in the cylinders. Another component of the system is the TDC sensor, which informs the control module that each piston has passed the top dead center position of its compression stroke. The information coming from the TDC sensor is used by the module to determine the injection sequence (and frequency).
When the ignition is turned on, the battery voltage is supplied to the primary winding of the ignition coil. The signals coming from the CKP sensor are converted by the control module into ignition control pulses and transmitted to the key transistor. The transistor ensures regular closure of the negative terminal of the primary winding of the coil to ground, as a result of which the secondary circuit of the coil induces voltage transmitted to the spark plugs.
When servicing direct ignition systems, special precautions must be taken:
- a) If the engine does not start, do not keep the ignition key turned to the ON position continuously for more than 10 seconds at a time;
- b) Make sure that the tachometer connection is carried out strictly in accordance with the manufacturers' instructions - some of the meters produced may not be suitable for use on these models;
- c) Never allow the ignition coil contact terminals to be grounded to ground - the slightest carelessness in this matter can lead to failure of the system components;
- d) Do not disconnect the battery while the engine is running;
- e) Ensure that components are properly grounded.
[The original article was published on: MitsubishiMan.ru]