Pontiac Fiero 1988 Service Manual page 475

6E2-A-20 DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI)
4-30-87
FUEL
PUMP
FUSE
ORN/BLK440 ECM
BAT
FUEL PUMP
RELAY
SWITCH
GRY 120
T M
FUEL PUMP RELAY
HARNESS
CONNECTOR
DK GRN/WHT 465 —
BLK/WHT 450
W24
— W12
12 VOLT
I — RELAY
DRIVE
ENGINE
GROUND
FUEL PUMP
(IN TANK)
BULKHEAD
^/CONN.
1
150
T
v
FUEL PUMP TEST
S> TERMINAL " G " OF ALDL
4-22-87
*7S 3947-6EA
CHART A-5
FUEL PUMP RELAY CIRCUIT
2.5L "P" SERIES (TBI)
Circuit Description:
When the ignition switch is turned "ON", the electronic control module (ECM) will activate the fuel pump
relay and run the in-tank fuel pump. The fuel pump will operate as long as the engine is cranking or running,
and the ECM is receiving ignition reference pulses.
If there are no reference pulses, the ECM will shut "OFF" the fuel pump within 2 seconds after key "ON".
Should the fuel pump relay, or the 12 volt relay drive from the ECM fail, the fuel pump will be run through
an oil pressure switch back-up circuit.
Diagnostic Aids:
An inoperative fuel pump relay can result in long
cranking times, particularly if the engine is cold or
engine oil pressure is low. The extended crank period
is caused by the time necessary for oil pressure to
build enough to close the oil pressure switch and turn
on the fuel pump.