(Pin 3 position at relay shown on this image) Ensure a fused power supply is present at the load circuit terminal of the relay whilst the ignition is switched on.Correct ground signal – Confirms that this section of the control circuit is not the cause of any inoperative fuel pump.No ground signal – would require further investigation of PCM or related connector.Activating the relay with a suitable scanner or cranking the engine should result in a ground circuit within the PCM for control wire from Pin 4 relay location shown on this image.(Pin 1 position at relay shown on this image)
(Pin 87 relay socket position wiring shown on this image) This needs to be tested at both the relay load circuit position as well as the fuel pump.
The load circuit from the relay to the fuel pump may be tested with a “known working” relay refitted to the pump relay socket and testing for correct power supply to the fuel pump.This power supply can be tested by a multimeter, generally during cranking to verify the Integrity of the power supply as there are multiple possible areas for voltage drop creation.This power supply to the fuel pump is interrupted of course by the relay when not activated.(Pin 30 relay socket position shown on this image) A fused power supply is present at the load circuit terminal of the relay whilst the ignition is switched on.(Pin 86 relay socket position shown on this image) The Earth condition must be tested to ensure relay activation.Correct signal – confirms that this section of the control circuit is not the cause of any inoperative fuel pump.No signal – would require further investigation of wiring from the PCM and if necessary, the PCM itself.(Pin 85 relay socket position shown on this image) Removing the pump relay and utilising a voltmeter or test light to test for 12V power supply whilst cranking or by using a suitable scanner to command PCM to operate the relay.On this system, the PCM will activate the relay with a power supply to the relay control circuit. Understanding the simple electrical control and load circuit types will assist the technician in quickly and accurately pinpointing the test procedure required for that specific circuit. There are of course many electrical circuit or fuel pump causes of “low or nil” fuel pressure or flow. What Technicians need to know when testing fuel pumps and related circuits when suspecting a fuel system fault. Member of Australian Automotive Aftermarket Association