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.
1987 Mercedes Benz 300DFACTORY OEM SERVICE PROCEDURE
Fuel Rack Position Sensor
- With engine off, turn safety sleeve of sensor counterclockwise. Disconnect connector on injection pump. Connect multimeter and set to ohm scale. Probe and check resistance of terminals No. 1 and 2. Resistance should be 23-27 ohms.
- Probe terminals No. 1 and 3. Resistance should be 23-27 ohms. Probe terminals No. 2 and 3. Resistance should be 46-54 ohms. If resistance is not to specification on any resistance tests, replace injection pump. If resistance was to specification on all tests go to next step.
- With engine off and ignition on, set multimeter to volts scale. Check voltage between terminals No. 1 and 2 on fuel rack position sensor connector. Voltage reading should be 10 volts. If voltage reading is 10 volts, testing is complete.
- If voltage reading is not 10 volts, repair open circuit. If no open circuit is found, replace EDS control unit. See Fig 1 .
Factory Service Tools
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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.