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 MANUALSTOYOTA19904RUNNER 2D UTILITY, 3.0 V, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 8 (BASIC TESTING - V6)FUEL PUMP CONTROL CIRCUITCIRCUIT OPENING RELAY
1990 Toyota 4Runner 2D Utility, 3.0 V, Standard
Circuit Opening Relay
1990 Toyota 4Runner 2D Utility, 3.0 V, StandardSECTION Circuit Opening Relay
WARNING: This page is about a different car, the 1989 Toyota Pickup, 1989 Toyota Camry, 1989 Toyota Cab & Chassis, and 1989 Toyota 4Runner. However, it is still accessible from the selected car via links, so may be relevant.
- Circuit opening relay controls fuel pump circuit. ECU receives an input signal at "STA" terminal when engine is cranking. This same starter signal is also applied to terminal "STA" of circuit opening relay.
- Starter signal energizes circuit opening relay during cranking, which in turn activates the fuel pump. On all models, when airflow meter senses airflow to engine, fuel pump switch in airflow meter provides the relay ground.
NOTE:
For more information on testing relays and fuel system components, see I - EFI SYS/COMP TESTS article.
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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.