5-2 FUEL SYSTEM
BASIC FUEL SYSTEM DIAGNOSIS
When there is a problem starting or driving a vehicle, two of the most
important checks involve the ignition and the fuel systems. The qu stions
most mechanics attempt to answer first, "is there spark?" and "is tt ere
fuel?" will often lead to solving most basic problems. For ignition: ystemFUEL LINES AND FITTINGS
» See Figures 1 and 2When working on the fuel system, insect the lines and connections for
cracks, leakage and deformation. Inspect the fuel tank vapor vent sj| item
hose and connections for looseness, sharp bends or damage. Chec; the
fuel tank for any deformation due to bad driving conditions. Inspect the
bands for rust or cracks. The tank bands should be secure and not pose.
Check the filler neck for damage or leakage.
Union Bolt Type
When disconnecting the high pressure fuel line, a large amount (
line will spill out, so observe the following.- Place a container under the connection.
- Slowly loosen the connection. Have a rag handy to clean up a
fuel.
gaso-y splitdiagnosis and testing, please refer to the information on engine electrical
components and ignition systems found earlier in this manual. If the igni-
tion system checks out (there is spark), then you must determine if the fuel
system is operating properly (is there fuel?).- Separate the connection.
- Plug the connection with a rubber plug.
- When connecting the union bolt on the high pressure line, always use
a new gasket. - Always tighten the union bolt by hand. Tighten the bolt to 22 ft. Ibs.
(29 Nm).
Flare Nut Type
Apply a light coat of engine oil to the flare and tighten the flare nut
by hand. Using a torque wrench, tighten the flare nut to 23 ft. Ibs. (31
Nm).Fig. 1 Inspect all fuel lines for cracks and leaks2 - 7 mm (0.08 - 0.28 in.)Pipe Hose-Clip0 - 3 mm (0 - 0.12 in.)Fig. 2 When placing a hose clamp, install in the position illus-
trated for a secure holdFUEL INJECTION SYSTEM
General Information
Fuel injected engines are equipped with the Toyota Computer Contrq Sys-
tem (TCCS). This integrated control system allows the Engine Control
ule (ECM) to control other systems as well as the fuel injection. On ear
systems, the fuel management was performed by the EFI computer; in t|ie
current system, the control unit also oversees ignition timing and advai
EGR funct on, idle speed control (ISC system), Electronically Controllei
Transmission (ECT) function as well as on-board diagnostics and back up or
fail-safe functions. The control unit is a sophisticated micro-computer, eceiv-
ing input signals from many sources and locations on the vehicle. It is Capa-
ble of rapid calculation of many variables and controls several output c|
simultaneously. This system is broken down into 3 major sub-systems: he
Fuel System, Air Induction System and the Electronic Control System. I
ing these divisions in mind will shorten troubleshooting and diagnosticAn electric fuel pump supplies sufficient fuel, under a constant pressure, to
the injectors. These injectors allow a metered quantity of fuel into the intake
manifold according to signals from the ECM. The air induction system pro-
vides sufficient air for the engine operation. This system includes the throttle
body, air intake device and idle control system components.Relieving Fuel System Pressure
CAUTION
Fuel injection systems remain under pressure after the engine
has been turned OFF. Properly relieve fuel pressure before dis-
connecting any fuel lines. Failure to do so may result in fire or
personal injury.