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Home >> Mercedes Benz >> 1991 >> 560SEC >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Fuel Delivery & System Pressures - Gasoline >> Fuel Distributor Delivery Volume
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Fuel Distributor Delivery Volume

  1. At fuel distributor, disconnect small diameter fuel return line connected between fuel distributor and diaphragm pressure regulator. Plug line. Connect hose with fitting to fuel distributor open port fitting. Place opposite end of hose in measuring container.
  2. For V8 engines, remove fuel pump relay (under hood near fuse panel). Bridge fuel pump relay connector pin sockets No. 7 and No. 8 with jumper wire to establish fuel pressure for one minute. Remove jumper wire. See Figure .
  3. For 4 and 6-cylinder engines, remove MAS unit from underhood component compartment area, near CIS-E control unit. To remove MAS unit, turn top knob from position No. 1 to position No. 0 and lift/pull MAS unit out of electrical connector socket. Using fused jumper wire, jumper connector pin socket No. 2 with battery voltage source to establish fuel pressure for one minute.
  4. Verify fuel delivery volume of 4.4-5.0 ozs. (.13-.15L) per minute with 11.5 volts to fuel pump. If delivery volume is low, replace fuel distributor or differential pressure regulator as required.
  5. When testing is completed, unplug and reconnect fuel distributor line. Tighten line fitting to 88-106 INCH lbs. (10-12 N.m). Install fuel pump relay or MAS unit. To install MAS unit, push MAS unit into electrical connector socket and turn top knob from position No. 0 to position No. 1.
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