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.
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HOMESERVICE MANUALSVOLVO1991240 L4-2.3L SOHC VIN 88 B230FREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSMAIN RELAY (COMPUTER/FUEL SYSTEM)DESCRIPTION AND OPERATIONFUEL PUMP RELAY (SYSTEM RELAY)
1991 Volvo 240 L4-2.3L SOHC VIN 88 B230F
Fuel Pump Relay (System Relay)
1991 Volvo 240 L4-2.3L SOHC VIN 88 B230FSECTION Fuel Pump Relay (System Relay)
The [1][2]system relay (located behind passenger side kick panel) is a combined function relay. It combines the fuel pump and fuel injection relay into one unit. The system relay provides current to the fuel pumps, suppressor relay, idle air valve, air mass meter, oxygen sensor pre-heating resistor and to other ECU controlled functions or components.
The fuel injection ECU controls the relay ground connection. When ground is supplied, the [1][2]system relay is activated and current can flow to all the related components. If the ground connection is interrupted, no current can reach the components. This enables the fuel injection ECU to control the fuel pump operation. The fuel pumps are activated only when the ECU receives an engine speed signal. Should the engine stop in case of an accident or other reason, the power supply to the fuel pumps will be interrupted by the system relay, reducing the risk of fire in case of a fuel leak.
The fuel injection ECU controls the relay ground connection. When ground is supplied, the [1][2]system relay is activated and current can flow to all the related components. If the ground connection is interrupted, no current can reach the components. This enables the fuel injection ECU to control the fuel pump operation. The fuel pumps are activated only when the ECU receives an engine speed signal. Should the engine stop in case of an accident or other reason, the power supply to the fuel pumps will be interrupted by the system relay, reducing the risk of fire in case of a fuel leak.
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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.