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 MANUALSVOLVO1991940 TURBO, 4D SEDAN, AW71LREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODESSELF-DIAGNOSTICS - FUEL INJECTIONCONTROL FUNCTION NO. 3TESTING FUEL SYSTEM COMPONENTS
1991 Volvo 940 Turbo, 4D Sedan, AW71L
Testing Fuel System Components
1991 Volvo 940 Turbo, 4D Sedan, AW71LSECTION Testing Fuel System Components
- Turn ignition on. Locate diagnostic unit, and remove its cover. Connect selector cable to socket No. 2. Depress push button 3 times. Each time the button is depressed, it should be held for more than 1 second and less than 3 seconds. While LED flashes, fuel injectors and idle valve should operate. Check by listening or feeling component when it is activated. If injectors fail to operate and LED flashes, proceed to step 2). If idle valve fails to operate and LED flashes, proceed to step 3).
- To test fuel injector circuit, connect an ohmmeter between harness side of terminals No. 9 (Orange wire on 240 Series; Blue/Yellow wire on all others) and No. 18 (Green/White wire on 240 Series; Gray wire on all others) of fuel system ECU connector. Resistance should be 4 ohms.
- If resistance is 5.3 ohms, one injector or wire to it is faulty. If resistance is 8.0 ohms, 2 injectors or wires to them are faulty. If resistance is 16 ohms, 3 injectors or wires to them are faulty. If resistance is incorrect, remove each injector connector. Each injector connector should have 16 ohms resistance. Repair as required.
- To test idle valve circuit, connect an ohmmeter between terminals No. 33 (Green/Red wire on 240 Series; Red/Black wire on all others) and No. 9 (Orange wire on 240 Series; Blue/Yellow wire on all others) of fuel system ECU connector. Resistance should be 8 ohms. If resistance is not as specified, check wiring and connections between idle valve and ECU. If wiring is okay, check idle valve. See IDLE VALVE in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE Section.
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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.