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.