Fuel Control

Fuel delivery is controlled by the control module system.
The diagnosis of fuel control starts with CHART A-3 ENGINE CRANKS BUT WILL NOT RUN.
Related Tests, Information and Procedures
This chart will test the fuel system and if there is a problem, will lead you to checking the fuel pump relay circuit, diagnosing the injector circuit or diagnosing the fuel system.

Fuel Injector
Testing the fuel injector circuit is in CHART A-3
with additional diagnosis in CHART A-4.
Related Tests, Information and Procedures
Chart A-4 Injector Circuit Diagnosis
A fuel injector which does not open may cause a "no start" condition. An injector which is stuck partly open could cause loss of pressure after sitting so long crank times would be noticed on some engines. Also, dieseling could occur because some fuel could be delivered to the engine after the key is turned "OFF."

Pressure Regulator
Testing the pressure regulator circuit is in CHART A-3 and CHART A-4.
Related Tests, Information and Procedures
Chart A-4 Injector Circuit Diagnosis
If the pressure regulator in the fuel injection unit supplies pressure which is too low, poor performance could result. If the pressure is too high, unpleasant exhaust odor may result.

Idle Air Control (IAC)
The diagnosis of idle Air Control (IAC) can be found in IDLE AIR CONTROL SYSTEM CHECK.
System Check - Idle Air Control (IAC )
If the IAC valve is disconnected or connected with the engine running, the idle RPM may be wrong. The IAC valve may be reset by disconnecting negative battery terminal for 10 seconds then reconnect battery cable, turn ignition "ON," engine "OFF" for 5 seconds then turn ignition "OFF" for 10 seconds.
The IAC valve affects the idle characteristics of the engine. If it is open fully, too much air will be allowed in the manifold and idle speed will be high. if it is stuck closed, too little air will be allowed in the manifold, and idle speed will be too low. if it is stuck part way open, the idle may be rough, and will not respond to engine load changes.

Fuel Pump Circuit
Diagnostic Trouble Code (DTC) 54 indicates a failure in the fuel pump circuit.
Powertrain Controls - ECM/PCM
The fuel pump relay has a connector pigtail located near the relay to assist in testing the system. By applying voltage at this terminal, it can be determined if the fuel pump will operate. This terminal will also prime the fuel line to the TBI/CMFI unit.
For diagnosis of the fuel pump relay circuit, refer to CHART A-5 FUEL PUMP RELAY CIRCUIT DIAGNOSIS.
Chart A-5 Fuel Pump Relay Circuit Diagnosis
An inoperative fuel pump will cause a "no start" condition. A fuel pump which does not provide enough pressure can result in poor performance.
An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The oil pressure switch will turn "ON" the fuel pump, as soon as oil pressure reaches about 28 kPa (4 psi).

IDLE SPEED
For Idle Air Control (IAC) check, refer to IDLE AIR CONTROL SYSTEM CHECK.
System Check - Idle Air Control (IAC )
^ System too lean (high air/fuel ratio) - Idle speed may be too high or too low. Engine speed may vary up and down, disconnecting IAC does not help. May set DTC 44.
Scan tool or voltmeter will read an oxygen sensor output less than 300 mV (0.3 volt). Check for low regulated fuel pressure or water in fuel. A lean exhaust with an Oxygen Sensor (O2S) output fixed above 800 mV (0.8 volt) will be a contaminated sensor, usually silicone. This may also set a DTC 45.
^ System too rich (low air/fuel ratio) - Idle speed too low. Scan counts usually above 80. System obviously rich and may exhibit black exhaust smoke. Scan tool and/or voltmeter will read an Oxygen Sensor (O2S) signal fixed above 800 mV (0.8 volt).