Pontiac Fiero 1988 Service Manual page 477

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6E2-A-22 DRIVEABILITY A N D EMISSIONS - F U E L INJECTION (TBI)

DK GRN/WHT 465

FUEL PUMP RELAY

v FUEL PUMP TEST

~ > TERMINAL "G" OF ALDL

*7S 3947-6EA

(Page 1 of 2)

FUEL SYSTEM DIAGNOSIS

2.5L " P " SERIES (TBI)

Circuit Description:

When the ignition switch is turned "ON", the electronic control module (ECM) will turn "ON" the in-tank

fuel pump. It will remain "ON" 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".

The pump will deliver fuel to the TBI unit, where the system pressure is controlled to 62 to 90 kPa (9 to 13

psi). Excess fuel is then returned to the fuel tank.

The fuel pump test terminal is located in the left side of the engine compartment. When the engine is

stopped, the pump can be turned "ON" by applying battery voltage to the test terminal.

Test Description:

Numbers below refer to circled

numbers on the diagnostic chart.

1. If fuse in jumper wire blows, check CKT 120 for a

short to ground.

Diagnostic Aids:

Improper fuel system pressure can result in one of

the following symptoms:

• Cranks, but won't run.

• Cuts out, may feel like ignition problem.

• Poor fuel economy, loss of power.

• Hesitation.

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