SERVICE MANUAL NUMBER 23
MULTI-PORT FUEL INJECTION DESCRIPTIONS AND SYSTEM OPERATION
Engine Control Module (ECM) and Delco EST Distributor System
The Delco EST Distributor operates independent of the ECM. Dwell time and spark advance
are controlled by the ECM. Voltage signals between the two are processed by the Ignition
Control (IC) module inside the distributor.
The ECM uses inputs from various sensors to calculate the ignition spark timing. It also uses
a signal from the IC module to tell it what the engine rpm is. A circuit within the IC module
converts the pickup coil voltage to a square wave engine rpm reference signal. This signal
is called Reference High (REF HI). The ECM needs something to compare the REF HI value
against. This is done by an additional signal called Reference Low (REF LO). These two
signals give the ECM precise engine rpm. Two other lines between the ECM and IC module
are called the bypass and IC circuits. They control the IC operation.
OncetheECMknowsiftheengineisinthecrankingorrunningmode,theECMwillelectroni-
cally control the spark timing accordingly.
Inside the distributor, the pick-up coil and pole piece will produce a voltage signal for cylinder
spark.
90-861326--1
MARCH 1999
Page 5B-25
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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