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Experience:  33 years exp. automotive repair NYS emisisions repair cert.
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1997 Saturn SC2 -- will not start. Spark tests OK. Cranks fine.

Customer Question

1997 Saturn SC2 -- will not start. Spark tests OK. Cranks fine. Seems to not be getting fuel - fuel line has fuel pressure. Starting fluid sprayed into air intake starts temporarily. Trying to figure out if computer is the issue or if there is something else that controls the injectors...
Submitted: 11 years ago.
Category: Car
Expert:  Marc replied 11 years ago.


Check all fuses first

The 1995–98 SOHC and all DOHC engines are equipped with Multi-port Fuel Injection (MFI), which utilizes one injector for each cylinder. All fuel injection and ignition functions are controlled by the Powertrain Control Module (PCM). It accepts inputs from various sensors and switches, calculates the optimum air/fuel mixture and operates the various output devices to provide peak performance within specific emissions limits. The PCM will attempt to maintain an air/fuel ratio of 14.6:1 in order to optimize catalytic converter operation. If a system failure occurs that is not serious enough to stop the engine, the PCM will illuminate the SERVICE ENGINE SOON light and operate the engine in a backup or fail-safe mode. In the backup mode, the PCM delivers fuel according to inputs from the Manifold Absolute Pressure (MAP) sensor and the Coolant Temperature Sensor (CTS). Other operating modes are in the PCM program and are described later.

Fuel is supplied to the engine from a pump mounted in the fuel tank. The fuel pump module includes the gauge/sending unit, which can be replaced separately. Otherwise, the module must be replaced as an assembly. The pump is operated through a relay mounted in the Instrument Panel Junction Block (IPJB), which is located under the center of the instrument panel on the passenger's side of the vehicle. A check valve in the tank unit maintains pressure in the system for a period of time after the engine is stopped to aid hot starting. The fuel tank must be removed to access the pump module.

Other system components include a pressure regulator, an Idle Air Control (IAC) valve, a Throttle Position Sensor (TPS), Air Temperature Sensor (ATS), Coolant Temperature Sensor (CTS), a power steering pressure switch and an oxygen sensor. The fuel injectors are solenoid valves that the PCM pulses on and off many times per second, in order to promote good fuel atomization. The pulse width determines how long the injector is on each cycle, and this regulates the amount of fuel supplied to the engine. Fuel injectors are operated simultaneously, not sequentially.

On 1991–97 models, the system pressure regulator is mounted on the end of the fuel rail that feeds the injectors. For 1998, all models have a new "Returnless" fuel system, which makes the pressure regulator an integral component of the fuel filter, which is mounted below the vehicle near the fuel tank. Intake manifold pressure is supplied to the regulator diaphragm, making system pressure partly dependent on engine load. The idle air control valve is a 2-coil stepper motor that controls the amount of air allowed to bypass the throttle plate. With this valve, the PCM can closely control idle speed even when the engine is cold or when there is a high engine load at idle.


You must check the fuel pressure with a gauge because it is critical it must be between 38-44 PSI Then you have to check the injector pulse with a noid light. This will tell you if the PCM is creating the ground path to open the fuel injector. (pulse)




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