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Re: Power to fuel pump?
You can double check your circuit by putting 12v to the fuel pump primer terminal in the underhood accessory wiring junction box. This bypasses the ECM controls and runs the fuel pump full time- then you can check back at the gas tank if the 12v is present constantly- I have included the fuel pump cicuit description below for you to ponder as well... good luck
Circuit Description
When the Ignition switch is first turned ON, the PCM energizes the fuel pump relay which applies power to the fuel pump through the high speed circuit (controlled by the fuel pump speed control relay). The fuel pump relay will remain ON as long as the engine is running or cranking and the PCM is receiving reference pulses. If no reference pulses are present, the PCM de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped. The fuel pump delivers fuel to the fuel rail and injectors, then to the fuel pressure regulator. The fuel pressure regulator controls fuel pressure by allowing excess fuel to be returned to the fuel tank. With the engine stopped, the fuel pump can be turn ON by using the scan tool output controls function.
The PCM alters fuel pump speed by energizing the fuel pump speed control relay Under normal conditions, the fuel pump control speed control relay is energized (normal fuel pump speed). The applied voltage to the fuel pump is controlled by a resistor assembly. When higher fuel volume is required due to increased engine load (MAP sensor value over 90 kPa). the PCM de-energizes the fuel pump speed control relay circuit. The increased voltage to the in-tank fuel pump allows a higher volume of fuel to be delivered to the fuel rail. The PCM also compensates for low system voltage by energizing the fuel pump speed control relay.
Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed through the wire insulation or a wire broken inside of the insulation.
Check for a poor connection or a damaged harness. Inspect the PCM harness and connectors for the following items:
Improper mating
Broken locks
Improperly formed or damaged terminals
Poor terminal to wire connections
Damaged harnesses
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Automotive A/C Engineer with:
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