Lexus SC300 / Lexus SC400. Service manual - part 507

5.  Check that there are no fuel leaks after performing any

maintenance on the fuel system.
(a)  Using SST, connect terminals +B and FP of the check

(”DIAGNOSIS”) connector.

SST 09843–18020
(b)  With engine stopped, turn the ignition switch ON.

(c)  When the fuel return hose is pinched, the pressure

within high pressure line will rise to approx. 392 kPa (4
kgf/cm2, 57 psi). In this state, check to see that there are
no leaks from any part of the fuel system.

NOTICE: Always pinch the hose. Avoid bending as it may
cause the hose to crack.

(d)  Turn the ignition switch OFF.
(e)  Remove the SST from the check connector.
SST 09843–18020

FI–16

EFI SYSTEM   –   Inspection Precautions

FUEL SYSTEM
Fuel Pump

ON–VEHICLE INSPECTION

1. 

CHECK FUEL PUMP OPERATION
(a)  Using SST, connect terminals +B and FP of the check

(”DIAGNOSIS”) connector.

SST 09843–18020
(b)  Turn the ignition switch ON.
NOTICE: Do not start the engine.

(c)  Check that there is pressure in the fuel inlet hose from

the fuel filter.

HINT: At this time, you will hear fuel return noise.

(d)  Turn the ignition switch OFF.
(e)  Remove SST from the check connector.
SST 09843–18020

FI–16

–

EFI SYSTEM

Fuel System (Fuel Pump)

If there is no pressure, check the following parts:

•

Fuses

•

EFI main relay

•

Fuel pump ECU

•

Fuel pump

•

Engine (& ECT) ECU

•

Wiring connections

2. 

CHECK FUEL PRESSURE
(a)  Check the battery voltage above 12 volts.
(b)  Disconnect the cable from the negative (–) terminal of

the battery.

CAUTION: Turn the ignition switch to ”LOCK”. Discon-
nect the cable from the negative (–) terminal of the bat-
tery. Wait at least 20 seconds before proceeding with
work.

(c)  Remove the union bolt holding the deliver pipe to the

No. 1 fuel pipe. Remove the two gaskets.

HINT:

•

Put a suitable container or shop towel under the delivery
pipe.

•

Slowly loosen the union bolt.

(d)  Install the No. 1 fuel pipe and SST (pressure gauge) to

the delivery pipe with three new gaskets and the union
bolt.

SST 09268–45012

Torque:     42 N

⋅

m (420 kgf

⋅

cm, 30 ft

⋅

lbf)

(e)  Wipe off any splattered gasoline.

(f)  Using SST, connect terminals +B and FP of the check

(”DIAGNOSIS”) connector.

SST 09843–18020
(g)  Reconnect the cable to the negative (–) terminal of the

battery.

–

EFI SYSTEM

Fuel System (Fuel Pump)

FI–17

(h)  Turn the ignition switch ON.
(i) 

Measure the fuel pressure.

Fuel pressure:     265–304 kPa

                   (2.7–3.1 kgf/cm, 38–44 psi)

If pressure is high, replace the fuel pressure regulator.
If pressure is low, check the following parts:

•

Fuel hoses and connections

•

Fuel pump

•

Fuel filter

•

Fuel pressure regulator

(j) 

Remove SST from the check connector.

SST 09843–18020

(k)  Start the engine.
(l)  Disconnect the vacuum sensing hose from the fuel

pressure regulator, and plug the hose end.

(m)  Measure the fuel pressure at idle.

Fuel pressure:      265–304 kPa

                     (2.7–3.1 kgf/cm, 38–44 psi)

(n) Reconnect the vacuum sensing hose to the fuel

pressure regulator.

(o)  Measure the fuel pressure at idle.

Fuel pressure:     196–235 kPa

                     (2.0–2.4 kgf/cm, 28–34 psi)

If pressure is not as specified, check the vacuum sensing
hose and fuel pressure regulator.
(p)  Stop the engine. Check that the fuel pressure remains

147 kPa (1.5 kgf/cm2, 21 psi) or more for 5 minutes after
the engine is turned off.

If pressure is not as specified, check the fuel pump, pressure
regulator and/or injectors.
(q)  After checking fuel pressure, disconnect the battery

negative (–) cable and carefully remove SST to prevent
gasoline from splashing.

SST 09268–45012
(r)  Connect the No. 1 fuel pipe to the delivery pipe with two

new gaskets and the union bolt.

Torque:      42 N

⋅

m (420 kgf

⋅

cm, 30 ft

⋅

lbf)

(s)  Reconnect the cable to the negative (–) terminal of the

battery.

(t)  Check for fuel leaks. (See page 

FI–15

)

FI–18

–

EFI SYSTEM

Fuel System (Fuel Pump)