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Home >> Mercedes Benz >> 1990 >> 300CE >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Fuel System >> Fuel Pump Delivery Volume
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Fuel Pump Delivery Volume

  1. Remove fuel pump relay from relay board (under hood on fuse panel). Check fuel pump current draws. Draw of 6 amps indicates fuel pump is good. Replace fuel pump if draw is more than 7 amps. Disconnect return line at diaphragm pressure regulator.
  2. Attach a hose to fitting on regulator. Place other end of hose in measuring glass or beaker. Bridge relay board terminals No. 7 and 8 with jumper wire and run fuel pump for 40 seconds. See FUEL PUMP PERFORMANCE tables.
  3. If delivery volume is low, ensure pump is receiving 11.5 volts. Check if dirty strainer in feed connection of fuel distributor is causing restriction. Check for pinched fuel lines.
  4. Pinch by-pass line-to-fuel inlet hose at fuel accumulator and repeat delivery volume test. If volume is correct, replace fuel accumulator. If volume is low, replace fuel filter and repeat test. Replace fuel pump if volume remains low. Reconnect fuel return line and install fuel pump relay.
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