Testing
GENERAL
Fuel 5
GENERAL
The tests outlined in this manual are for checking Throttle Body Fuel Injection (TBI) (see
Figure 2) and Multi-port Fuel Injection (MFI) (see Figure 3) fuel system pressures with the
engine running (key on, engine on) and without the engine running (key on, engine off).
Engine running tests are performed with the engine at idle (unless otherwise noted). The
adapter for testing GM vehicles with test ports is already installed on the end of the gauge
hose, while the Ford adapter is separate. For Chrysler vehicles, depending upon
application, either adapter may be used.
Some fuel injection systems are not equipped with a test port (Schrader valve). In some
cases, these systems may be tested using the tee adapter provided with the tester:
• The tee adapter is suitable for use with most fuel injection systems equipped with rubber
fuel hoses secured by fuel line clamps at the fuel rail or throttle body (see Figure 6).
• The tee adapter is not suitable for use with fuel injection systems equipped with rigid,
metallic or plastic fuel lines or connectors.
Figure 2. Typical Throttle Body Fuel Injection (TBI) Systems
TBI UNIT
FUEL INJECTORS
THROTTLE BODY
PRESSURE REGULATOR
FUEL CAP
FUEL RETURN LINE
IN-LINE
FUEL FILTER
FUEL PRESSURE LINE
FLEXIBLE HOSE
FUEL TANK IN-TANK
FUEL PUMP
PUMP INLET
FILTER
FUEL INJECTORS
PRESSURE
REGULATOR
MANIFOLD VACUUM
HOSE CONNECTION
TEST PORT
(SCHRADER
VALVE)
PULSE
DAMPENER
FLEXIBLE
HOSE
IN-LINE
FUEL FILTER
FUEL RETURN LINE
FUEL PRESSURE LINE
FUEL
CAP
FUEL TANK PUMP INLET
FILTER
IN-TANK
FUEL PUMP
PULSATOR
Figure 3. Typical Multi-Port Fuel Injection (MFI) System
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