Fuel Pressure

Basic diagnosis of fuel system should begin with determining fuel system pressure.

WARNING: ALWAYS relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components.

Check fuel pressure. Ensure a sufficient amount of fuel is in fuel tank. Turn ignition off. Locate check connector. See Fig 1 or Fig 2. Using a jumper wire, connect check connector terminals +B and FP. See Fig 3. Turn ignition on.

Fig 1: Locating Check Connector (ES250)
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 2: Locating Check Connector (LS400)
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Using fingers, ensure fuel pressure is felt in hose from fuel filter. When fuel system is pressurized, fuel return noise will also be heard. Turn ignition off.
If no fuel pressure was felt, check fusible links, fuses (EFI 15-amp and IGN 7.5-amp), EFI main relay, fuel pump, ECU and wiring connections.
CAUTION: SLOWLY loosen cold start injector fuel line to avoid fuel spraying onto skin, eyes and vehicle finish.
Connect fuel pressure gauge to cold start injector fuel line. Using a jumper wire, connect terminals FP and +B of check connector. See Fig 3. Turn ignition on. Check fuel pressure.

See FUEL PRESSURE SPECIFICATIONS TABLE. If fuel pressure is more than specification, replace fuel pressure regulator. If fuel pressure is less than specification, check fuel hoses, hose connections, fuel pump, fuel filter and fuel pressure regulator. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

FUEL PRESSURE SPECIFICATIONS

Application

psi (kg/cm² )

Ignition On, Engine Off

38-44 (2.7-3.1)

Engine Idling ⁽¹⁾

38-44 (2.7-3.1)

Engine Idling ⁽²⁾

33-37 (2.3-2.6)

Ignition Off, Engine Off

21 (1.5)

⁽¹⁾	With fuel pressure regulator vacuum hose disconnected.

⁽²⁾	With fuel pressure regulator vacuum hose connected.

Fig 3: Identifying Check Connector Terminals

CAUTION: DO NOT confuse check connector terminal connection as this may create additional malfunctions.

Start engine. Disconnect and plug vacuum hose from fuel pressure regulator. Check fuel pressure. See FUEL PRESSURE SPECIFICATIONS TABLE Unplug and reconnect vacuum hose to fuel pressure regulator.
Check fuel pressure. See FUEL PRESSURE SPECIFICATIONS TABLE. If fuel pressure is not within specification, check fuel pressure regulator and vacuum hose.
Turn engine off. Ensure fuel pressure does not drop to less than specified value for 5 minutes after engine is turned off. See FUEL PRESSURE SPECIFICATIONS TABLE.
If fuel pressure is not as specified, check fuel pump, fuel pressure regulator and fuel injectors. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Remove fuel pressure gauge.