Mercury MerCruiser MCM 454 Mag MPI Service Manual page 675

GENERAL SYSTEM DIAGNOSTICS
Chart A-6 (1 of 2): EFI System/Ignition Relay Check
CIRCUIT DESCRIPTION:
Battery voltage is constantly supplied to terminal "30" of the system relay. When the ignition
switch is moved to the "RUN" position, battery voltage is supplied to terminal "86" of the sys-
tem relay. The pull-in coil is then energized creating a magnetic field which closes the con-
tacts of the system relay. Voltage and current are then supplied to the ignition control mod-
ule, injectors, ECM, and fuel pump relay through terminal "87" CKT 902 of the system relay.
DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed through wire insulation or a
wire broken inside the insulation. Check for the following items:
Poor connection or damaged harness. Inspect the ECM harness and connectors for
improper mating,broken locks, improperly formed or damaged terminals, poor terminal
to wire connection, and damaged harness.
Contaminated or dirty fuel may cause the fuel pump to seize, which will cause the fuel
pump relay fuse to fail.
TEST DESCRIPTION:
Number(s) below refer to the Step number(s) on the Diagnostic Table:
2. Verifies that there is power to the system relay.
3. This step checks if there is an open in the ground circuit.
Index
Page 5E-82
Downloaded from https://needmanual.com/
a
b
c
d
a - From 5-pin Connector
b - 50a Circuit Breaker
c - 90 Amp Fuse
d - Battery
e - System Relay
f - To ECM Term "J1-11"
g - Injector/Ks Module Fuse 10a
h - To Fuel Pump Relay Fuse 15a
i - To Ignition Coil Term "8"
j - Engine Ground
SERVICE MANUAL NUMBER 23
86 85
30 87
902 RED
e
f
g
90-861326--1 MARCH 1999
j
h
i