Part 1 of 2

Chart A-7 - Fuel System Diagnosis (2 Of 2):

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
Number below refers to circled number on the diagnostic chart.
1. Fuel pressure should be noted while fuel pump is running. Fuel pressure will drop immediately after fuel pump stops running due to a controlled bleed in the fuel system.

DIAGNOSTIC AIDS:
Improper fuel system pressure can result in one of the following symptoms:
- Cranks, but won't run
- Code 44
- Code 45
- Cuts out, may feellike ignition problem
- Poor fuel economy, loss of power
- Hesitation