Fuel Pump, Pressure Regulator and Relay

Fuel pressure and pressure regulator functionality

  • Connect pressure gauge KDEP 1034 as described in the Component Test Instructions.
  • Turn on the ignition.
  • Deflect air flow meter flap by hand to operate fuel pump.
  • Measure the fuel pressure and pressure regulator function.

Fuel pressure should be at 2.2-2.6 bar.

  • No pressure buildup (pump does not start): Pull plug from pump and measure voltage at plug contacts. If reading is 12 Volts, pump is defective. If reading is 0 Volts, check pump fuse in B+ line to relay terminal 88y. If relay is operating, then check cable from relay terminal 88d to pump. If cable is OK, relay is defective.
  • Pressure above or below specification: Check fuel filter and return lines for free passage. If all fuel lines are OK, pressure regulator is defective.

Fuel pump delivery quantity

  • Remove fuel hose from cold start valve and place in a graduate.
  • Turn on the ignition.
  • Deflect air flow meter flap by hand to operate fuel pump.

1.5-2.0 liters per minute should flow out of the fuel hose. If fuel filter and lines are free and correct delivery quantity cannot be reached, fuel pump is defective.