Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Main Relay (Computer/Fuel System): Description and Operation
1994 Jaguar XJ-6 L6-4.0LSECTION Description and Operation
PURPOSE
The main relay supplies power to the supplementary air valve, air mass meter, fuel injectors and fuel pump relay.
The relay also applies power to the ECM, generating a system reset which causes the microprocessor to perform an initialization routine, condition input circuits for sensor scanning and run the fuel pump to pressurize the system for starting. The fuel pump relay is ECM timed to limit fuel pump operation to approximately 0.5 second prior to cranking.
OPERATION
The relay is energized when the ignition "ON" relay is energized by turning the ignition switch to position "II."
LOCATION
Right rear corner of engine compartment.
The main relay supplies power to the supplementary air valve, air mass meter, fuel injectors and fuel pump relay.
The relay also applies power to the ECM, generating a system reset which causes the microprocessor to perform an initialization routine, condition input circuits for sensor scanning and run the fuel pump to pressurize the system for starting. The fuel pump relay is ECM timed to limit fuel pump operation to approximately 0.5 second prior to cranking.
OPERATION
The relay is energized when the ignition "ON" relay is energized by turning the ignition switch to position "II."
Relay Locations And I.D.:
LOCATION
Right rear corner of engine compartment.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.