1993 Volvo 850 AutomaticFACTORY OEM SERVICE PROCEDURE

Fuel Pump Circuit (850)

  1. If fuel pump does not operate with ignition on, remove fuel pump relay. See Figure . Connect jumper wire between fuel pump relay terminals No. 1 and 3. See Figure . Turn ignition on. If fuel pump does not start, go to next step. If fuel pump starts, replace fuel pump relay.
  2. Turn ignition off. To check relay ground, connect ohmmeter between ground and fuel pump relay terminal No. 2. See Figure . Ohmmeter should indicate about zero ohms. If ohmmeter does not indicate about zero ohms, check wiring between fuel pump relay and ground.
  3. To check fuel pump relay voltage supply, connect voltmeter between ground and fuel pump relay terminal No. 1. See Figure . Turn ignition on. Battery voltage should be present. If battery voltage is not present, check wiring between fuel pump relay and fuse No. 2.
  4. Turn ignition off. Connect ohmmeter between ground and relay terminal No. 3. See Figure . About 1.5 ohms should be present. If about 1.5 ohms are not present, check resistance at fuel pump connector to determine whether fault is in pump or wiring.
  5. To check fuel injection control signal to fuel pump relay, connect voltmeter between ground and fuel pump relay terminal No. 4. See Figure . Operate starter motor. If voltmeter indicates about 3 volts, replace relay. If voltage is not to specification, check wiring between fuel pump relay and ECU. If wiring is okay, see ELECTRONIC CONTROL UNIT - IGNITION in the SYSTEM/COMPONENT 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.

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