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 DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - BASIC TESTING - EFIFUEL PUMP CONTROL CIRCUIT TESTCIRCUIT 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
- 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 except Celica, Corolla (4A-FE), Supra (7M-GTE) and Tercel, when airflow meter senses airflow to engine, fuel pump switch in airflow meter provides the relay ground. On Celica, Corolla (4A-FE), Supra (7M-GTE) and Tercel, circuit opening relay is grounded by ECU through FC terminal.
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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.