Fuel Pressure
Fuel system diagnosis should begin with determining fuel system pressure. If fuel pump does not run, inspect fuel pump fuse in fuse panel. If fuse is not blown, see FUEL PUMP and FUEL PUMP RELAY in I - 4-CYL SYS/COMP TESTS article. Refer to WIRING DIAGRAMS article for specific circuit or wire color reference.
CAUTION:
High fuel pressure may be present in fuel lines and component parts on some models. Relieve pressure before attempting to open system for testing or component replacement. DO NOT
allow fuel to flow onto engine or electrical parts or allow an open flame in area while testing fuel system components.
- Relieve fuel system pressure. To relieve pressure, remove fuel pump fuse, start engine and allow to run until engine stalls due to lack of fuel. Crank engine an additional 2 or 3 times to verify all pressure has dissipated.
- On Pathfinder, Pickup and Sentra, disconnect fuel inlet hose at fuel injection body. On all other models, disconnect fuel hose on fuel filter inlet side. On all models, install fuel pressure gauge.
- Start engine and check fuel line connections for leakage. Check fuel pressure with engine idling. Record fuel pressure gauge reading. Disconnect vacuum hose from pressure regulator and immediately note fuel pressure. Record fuel pressure gauge reading. See REGULATED FUEL PRESSURE table.
REGULATED FUEL PRESSURE (4-CYLINDER)
| Model/Application | At Idle w/o Vacuum psi (kg/cm2 ) | At Idle w/Vacuum psi (kg/cm2 ) |
|---|---|---|
| Pathfinder & Pickup | 44 (3.1) | 36 (2.5) |
| Pulsar NX SE | 43 (3.0) | 36 (2.5) |
| Pulsar NX XE | N/A | 43 (3.0) |
| Sentra | N/A | 43 (3.0) |
| Stanza | 44 (3.1) | 37 (2.6) |
| 240SX | 43 (3.0) | 33 (2.3) |