Skylark V6-3100 3.1L VIN M SFI (1996)
Fuel Tank Unit: Description and Operation
Modular Fuel Sender Assembly
MODULAR FUEL SENDER ASSEMBLY
The modular fuel sender assembly (3), mounts in the top of the fuel tank and is spring loaded to the bottom. It is designed to:
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Provide optimum fuel level in the internal fuel reservoir during all fuel tank levels and driving conditions.
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Improve the measuring accuracy of fuel tank level.
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Filters coarse contaminates from the fuel
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House fuel pump and helps prevent fuel pump noise.
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Include a check valve to inhibit back flow of fuel from fuel system.
The modular fuel sender assembly consists of the following serviceable components:
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Fuel strainer
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Level sensor.
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Fuel tank vapor pressure sensor.
FUEL PUMP OPERATION
An electric fuel pump, located in the modular sender assembly (3), is used to provide fuel pressure. The fuel pump is not serviced separately. The
modular sender assembly must be serviced as a complete unit.
To control fuel pump operation, a fuel pump relay and fuel pump switch are used. When the ignition lock cylinder is turned to RUN position, the
fuel pump relay activates the electric fuel pump for approximately two seconds to prime the injectors. If the PCM does not receive reference
pulses after this time, the PCM opens the fuel pump relay ground circuit. The relay will reactivate the fuel pump when the PCM receives reference
pulses or when oil pressure raises.
When the key is first turned ON, without the engine running, the PCM energizes the fuel pump relay for a calibrated time (approximately 2
seconds). This builds up fuel pressure quickly. Whenever the engine is not started within two seconds, the PCM shuts OFF the fuel pump and
waits until ignition reference pulses are present.
As soon as the engine is cranked, the PCM energizes the relay which powers the fuel pump. As a backup system to the fuel pump relay, the fuel
pump also can be energized by the fuel pump and engine oil pressure indicator switch. The fuel pump and engine oil pressure indicator switch is a
normally open switch which closes when oil pressure reaches about 28 kPa (4 psi). Whenever the fuel pump relay fails, the fuel pump and engine
oil pressure indicator switch powers the fuel pump. An inoperative fuel pump relay can result in long cranking times. An inoperative fuel pump
would cause a no start condition. A fuel pump which does not provide enough pressure can result in poor performance.
