Part 2 of 4

Fuel Delivery Schematic (Tools Shown Installed For Testing):

Chert A-7, Fuel System Pressure Test (2 Of 4):

CIRCUIT DESCRIPTION:
The fuel pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator, where the system pressure is controlled. Excess fuel pressure is bypassed back to the fuel tank. When the engine is stopped, the pump can be turned "ON" by applying battery voltage to the test terminal located in the engine compartment. Improper fuel system pressure may contribute to Codes 44 or 45, cuts out which may feel like an ignition problem, hesitation loss of power or cause a "Cranks But Won't Run" condition.


TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
5. Fuel pressure that drops off during acceleration, cruise at speed, or hard cornering may cause a lean condition and result in loss of power, surging, misfire, or even backfire and stall. This condition can be diagnosed using a "Scan" tool. If the system is very lean, the oxygen sensor voltage will drop and become fixed below 500 millivolts and the injector pulse width will increase.

NOTE: Make sure the system is not operating in "fuel Cut-Off" mode, as this will cause false readings on the "Scan" tool.

6. Fuel pressure below 284 kPa (41 psi) may cause a lean condition and may set a Code 44 or 32. Driveability conditions can include hard starting cold, hesitation, poor driveability, lack of power, surging, misfire, backfire, or stalling.
. Restricting the fuel return line causes fuel pressure to increase above regulated pressure. With the fuel pump operating, pressure should rise above 325 kPa (47 psi) as the return line is partially closed off.

Caution: Do not allow pressure to exceed 414 kPa (60 psi) or the regulator will be damaged.

8. Fuel pressure greater than 325 kPa (47 psi) may cause a rich condition and may set a Code 45. Driveability conditions can include hard starting (followed by black smoke) and a strong sulphur smell in the exhaust.
9. this test determines if the high fuel pressure is due to a restricted fuel return line or a faulty pressure regulator.