PleasureCraft Engine Group 5.0L, Diagnostic Manual

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5.0/5.7L Distributor Ignition 4A - 3
MEFI 4 - PCM
Distributor Ignition (DI) System Description
Ignition System Overview
The ignition system consists of the following components
or circuits:
•
The 8 ignition secondary wires
•
The ignition coil
•
The ignition control (IC) circuit
•
The camshaft position (CMP) sensor
•
The camshaft reluctor wheel
•
The crankshaft position (CKP) sensor
•
The crankshaft reluctor wheel
•
The related connecting wires
•
The engine control module (ECM)
To properly control ignition timing, the ECM relies on the
following information:
•
Engine load, manifold pressure or vacuum
•
Atmospheric, barometric, pressure
•
Engine temperature
•
Intake air temperature, if applicable
•
Engine speed (RPM)
The ignition control utilizes the following to control spark
timing functions:
•
The 4X signal - The 4X crankshaft position sensor
sends a signal to the ECM. The ECM uses this
signal to determine crankshaft position, or engine
speed.
•
The 1X signal - The 1X camshaft position sensor
sends a signal to the ECM. The ECM uses this
signal to quickly determine what cylinder to fi re the
ignition coil on.
•
The ignition control (IC) circuit - The ECM uses this
circuit to trigger the ignition coil.
The distributor used on the MEFI equipped engines is
designed for the marine/industrial environment. The base
plate of the distributor is equipped with two special vents
to prevent any fuel vapors from igniting. With the high
voltage produced by the distributor, a special material is
used for the distributor cap and rotor. It is a thermoplastic,
injection-molded, glass-reinforced polyester. This material
provides the dielectric and insulation property needed, and
also prevents carbon tracking.
Distributors with separate coils are used on the MEFI
engines. The ignition coil connects to the distributor cap
through a high tension wire.
There is no scheduled maintenance or periodic lubrication
required. Engine oil lubricates the lower bushing and the
upper bushing is pre-lubricated and sealed.
M4088
The crankshaft position (CKP) sensor is a magneto
resistive type sensor. The CKP sensor works in
conjunction with a 4X reluctor wheel. The reluctor wheel is
mounted on the front of the crankshaft. The CKP sensor
outputs a 4X signal for spark control, tachometer output
and fuel control. All CKP signals are output as a digital
waveform.
The 5.7L, right-hand rotation, uses a different crankshaft
reluctor wheel than a normal, left-hand rotation engine.
Crankshaft Position (CKP) Sensor and Reluctor
Wheel