Prizm L4-1600cc 1.6L DOHC VIN 5 (1989)
Fuel Fluid Diagram
CIRCUIT DESCRIPTION:
The fuel pump delivers fuel to the fuel rail and injectors, where the system pressure is controlled from 265 to 304 kPa (38 to 44 psi) by the pressure
regulator. Excess fuel is returned to the fuel tank. When the engine is stopped, the pump can be energized by applying battery voltage to the test terminal
located in the engine compartment. With engine turned "OFF," fuel pressure should remain above 147 kPa (21 psi) for five minutes.
TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.
5.
Pressure less than 265 kPa (38 psi) may be caused by one of two problems. The regulated fuel pressure is too low. The system will be running lean
and may set Code 25. Also, hard cold starting and overall poor performance is possible. Restricted flow is causing a pressure drop. Normally, a
vehicle with a fuel pressure loss at idle will not be driveable. However, if the pressure drop occurs only while driving, the engine will surge and
then stop as pressure begins to drop rapidly.
6.
Restricting the fuel return line allows the fuel pump to build above regulated pressure. When battery voltage is applied to the fuel pump test
terminal, pressure should be above 450 kPa (65 psi).
7.
This test determines if the high fuel pressure is due to a restricted fuel return line or a pressure regulator problem.
