GENERAL SYSTEM DIAGNOSTICS
SERVICE MANUAL NUMBER 23
Chart A-5 (1 of 3): Fuel System Electrical Test
ECM
a
902
RED
339 PNK/BLK
b
87a
30
c
e
85
465 DK GRN/WHT
J2-9
86
87
450 BLK/WHT
120 GRY
A
M
B
150 BLK
d
a - To System Relay
b - Fuel Pump Relay Fuse 15a
c - Fuel Pump Relay
d - Fuel Pump
e - Fuel Pump Relay Driver
CIRCUIT DESCRIPTION
The fuel system circuit receives a supply voltage from the system relay CKT 902. The fuel
system is protected by a 15 amp fuse. After the fuse, supply voltage is delivered by CKT 339
to fuel pump relay terminal “30.” The fuel pump relay is turned on by the ECM by supplying
voltage to CKT 465. The fuel pump relay will remain “ON” as long as the engine is running
or cranking and the ECM is receiving reference pulses. If no reference pulses are present,
the ECM de-energizes the fuel pump relay within 2 seconds after the ignition is turned “ON”
or the engine is stopped.
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 connections 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.
3.
Verifies that there is power to the fuel pump relay.
Bypassing the relay circuit should cause the fuel pump to run. This step should identify
if the fault is in the relay or in the fuel pump circuit.
4.
5.
This step checks if there is an open in the ground circuit.
This step checks if the ECM is functioning properly.
Index
Page 5E-78
90-861326--1 MARCH 1999
| 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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