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Home >> Mercedes Benz >> 1988 >> 560SL >> Repair and Diagnosis >> Engine Performance >> System >> Cis-E System >> Component Testing >> Electrical Components >> Fuel Pump Relay
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Fuel Pump Relay

  1. Remove fuel pump relay from board. Connect positive lead of multimeter to socket No. 8 (terminal No. 30) and negative lead to socket No. 11 (terminal No. 31) of connector. Measure voltage. If reading is 12 volts, go to step 3). If reading is zero volts, go to next step.
  2. Remove negative lead of multimeter from socket No. 11 (terminal No. 31) and connect to vehicle ground. If reading is 12 volts, check Brown wire from terminal No. 31 for short. If voltage is zero, check Red wire from terminal No. 30 for short. Repair wiring if necessary.
  3. Switch on ignition and check voltage at socket No. 9 (terminal No. 15) of connector. If reading is zero volts, check Black/Red wire from terminal No. 15 to fuse box for short. Repair wiring if necessary. If reading is 12 volts, go to next step.
  4. Using dwell meter, connect positive lead to socket No. 10 (terminal TD). Dwell angle should be 7-34 degrees. If dwell is incorrect, check Green/Yellow wire from jack 10 (terminal TD) to TZL (transistor ignition) switching unit for short. If wiring is good, replace switching unit. If dwell reading is good, go to next step.
  5. Bridge socket No. 7 (terminal No. 87) and socket No. 8 (terminal No. 30) with jumper wire. If fuel pump is running, test is completed. If fuel pump is not running, go to next step.
  6. Check Black/Red/White wire from terminal No. 87 to fuel pump for short. If wiring is good, replace fuel pump relay. If fuel pump still does not run, replace fuel pump.
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