Ford LRG-423 Service Manual page 112

03-3 Auxiliary Systems 03-3
DISTRIBUTORLESS IGNITION SYSTEM DESCRIPTION AND OPERATION
Warning
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High tension voltage produced by a distributorless
ignition system is higher than for a conventional
ignition system.
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When carrying out service operations on an engine
equipped with distributorless ignition. It is important
to be aware of the above point as well as all the
usual safety measures to prevent the possibility of
electric shocks.
Description
The purpose of an engine' s ignition system is to ignite
the fuel/air mixture at the correct time and sequence
based upon the input it receives.
The Distributorless Ignition System (DIS) used on the
LRG 423 engine is state of the art. The brain of this
system is the Universal Electronic Spark Control
(UESC) module. This module receives four inputs:
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Crankshaft position
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Crankshaft speed
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Engine temperature
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Engine vacuum (load)
From these inputs, the UESC computes spark strategy
(spark advance) to obtain optimum engine
performance for correct input conditions.
Operation
With this system, the electronic control module
monitors the engine load, speed and operating
temperature and decides what degree of spark
advance is correct for all of the operating conditions.
Because timing is set for life inherently in the design of
the engine, and there are no moving parts in the
ignition system itself, no maintenance is required
except for periodic spark-plug checks. The system
provides for fixed spark advance at start-up, for cold
weather starting, and for " average value" default
settings in case of component failure. Particular
attention has been given to spark optimization for
excellent fuel economy in the warm-up mode.
The spark plugs are paired so that one plug fires
during the compression stroke and its companion plug
fires during the exhaust stroke. The next time that coil
is fired, the plug that was on exhaust will be on
compression, and the one that was on compression
will be on exhaust. The spark in the exhaust cylinder is
wasted but little of the coil energy is lost.
COMPRESSION
STROKE
EXHAUST
STROKE
PPD0002