Results of Incorrect Operation
Open or Grounded REF HI Line - This line provides
the ECM with engine speed information. If this line is
open or grounded, the ECM will not know that the en-
gine is cranking or running and will not run.
Open IC Line from the ECM to the Distributor
Module - While the engine is cranking, the ECM ex-
pects to see the IC signal pulled to virtually zero be-
cause it is grounded in the distributor module. Since
the IC line is open, it cannot be grounded by the mod-
ule and the IC signal will be able to rise and fall, or do
what is called toggling. The ECM recognizes the tog-
gling as an abnormal condition, and will not apply by-
pass voltage to the distributor module when the en-
gine reaches run RPM.
Open or Grounded REF LO Line - This wire is
grounded in the ignition module and provides a refer-
ence ground from the ignition module to the ECM.
The ECM compares reference ground with reference
high voltage. If this circuit is open, or grounded at any
other location than through the module, it may cause
poor performance.
Since bypass voltage is not applied to the relay, it re-
mains open and the engine continues to run on the
pickup coil triggering in the ignition module timing
mode.
Fuel Metering System
If this condition occurs while the engine is running,
the engine will stop, but it will restart and run in the
ignition module timing mode with reduced power.
General Description
The function of the fuel metering system is to deliver
the correct amount of fuel to the engine under all op-
erating conditions.
Multi-Port Injection, fuel is delivered to the engine
by individual fuel injectors mounted in the intake
manifold near each cylinder.
Grounded IC Line - During cranking, the IC voltage
is at virtually zero so the ECM does not recognize a
problem. When engine RPM reaches the value for
the run condition, the ECM applies bypass voltage to
thedistributormodule.Bypassvoltageonthemodule
switches the distributor power transistor to the IC
line. Because the IC line is grounded, it will have no
voltage applied so it cannot operate the power tran-
sistor to enter the IC mode.
Throttle Body Injection, fuel is delivered from two
injectors mounted atop the intake manifold.
Modes of Operation
If the IC line becomes grounded while the engine is
being operated, the engine will stop and will be diffi-
cult to restart.
The ECM looks at voltages from several sensors to
determine how much fuel to give the engine. The fuel
is delivered under one of several conditions, called
modes. All the modes are controlled by the ECM and
are described below.
An open or ground in the IC or bypass will cause the
engine to run on the distributor module timing. This
will cause reduced performance, poor fuel economy
and erratic idle.
STARTING MODE
Grounded or Open Bypass Line - While the engine
is cranking, the IC line will be grounded and the ECM
will not notice anything abnormal. When run RPM is
reached, the ECM applies bypass voltage to the by-
pass line but because of the ground or open, it will not
be able to energize the relay. Therefore, the relay will
stay de-energized and the IC line will remain
grounded.
When the ignition switch is turned to the crank posi-
tion, the ECM turns ON the fuel pump relay and the
fuel pump builds up pressure. The ECM then checks
the Engine Coolant Temperature (ECT) sensor and
Throttle Position (TP) sensor and determines the
proper air/fuel ratio for starting. The ECM controls the
amount of fuel delivered in the starting mode by
changing how long the injectors are turned ON and
OFF. This is done by pulsing the injectors for very
short times.
When the ECM sees the IC line not toggling, it will not
enter the IC mode. Since the relay is de-energized,
the engine will continue to run in the ignition module
timing mode.
If this condition occurs while the engine is running,
the engine will simply operate in the ignition module
timing mode.
Index
5C-20 - ELECTRONIC FUEL INJECTION (MULTI-PORT AND THROTTLE BODY)
90-823224--2 796
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1993, 1994, 1995, 1996, 1997 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
(4 votes, average: 4.5 out of 5)
Marine readers have rated 1993 1997 Mercury-MerCruiser GM V8 454 CID 7.4L and 502 CID 8.2L Marine Engines Service Manual Number 16 4.5 out of 5.0 based on 4 product reviews. Hugely helpful service manual! Perfect. Thank you!
Manuals are all Important for Technician
This book is invaluable if you do your own repairs. Great book.
Could not find a copy until a search brought me here.
Excellent print.
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