Fuel Delivery Rate, Checking
Special Tools And Workshop Equipment Required
- Diesel Pressure Tester Kit:VAS6551
- Diesel Pressure Tester Kit - Hose 2:VAS6551/2
- Diesel Pressure Tester Kit - Adapter Set - Adapter 1:VAS6551/5-1
- Diesel Pressure Tester Kit - Adapter Set - Connection Hose 2:VAS6551/5-2
- Diesel Pressure Tester Kit - Adapter Set - Connection Hose 3:VAS6551/5-3
- Diesel Pressure Tester Kit - Adapter Set - Connection Hose 4: VAS6551/5-4
- Pressure Regulator Valve:VAS6551/6
- Vehicle Diagnostic Tester
- Measuring Container
- Wiring Diagram
Test conditions:
- The engine control module DTC memory does not contain a DTC memory entry related to the power supply of the fuel pump.
- Fuel Pump Control Module -J538- is OK
- Battery charger connected. Refer to BATTERY .
- Fuel pump fuse OK; for the fuse assignment. Refer to Wiring Diagram.
- Fuel filter OK.
- Fuel tank minimum 3 /4 full.
- Ignition is switched off.
A second mechanic is needed for the following task.
Check the fuel delivery rate between the fuel filter and the high pressure pump:
-- Remove the fuel supply line to the high pressure pump. Refer to -item ) OVERVIEW - FUEL FILTER - SUPPLY LINE.
-- Connect the :VAS6551/5-2 to the connection -B- from the :VAS6551 .
-- Connect the :VAS6551/5-2 on the connection for the fuel supply line on the fuel filter.
-- Secure the fuel supply line with hose clamps. Ensure proper seating of the hose clamps.
-- Connect the :VAS6551/6 to the connection -B- on the :VAS6551 .
-- Hold the open end of the :VAS6551/6 hose in a measuring container.
-- The shut-off valves -A- and -B- are open on the :VAS6551 -1-.
-- The shut-off valve -C- on the :VAS6551 -1- must be closed.
-- Connect the Vehicle Diagnostic Tester.
-- Select the 0001 activate fuel pump Guided Function.
-- Select the Check fuel pump delivery pressure/delivery quantity function.
-- Follow the instructions on the Vehicle Diagnostic Tester.
-- Set the pressure to 4.0 bar using the :VAS6551/6 .
-- The initial pressure is set by turning the adjusting wheel -arrow- on the :VAS6551/6 .
- Specified value: 4.5 bar pressure.
-- Do not move the adjusting wheel -arrow- anymore.
-- Empty the measuring container.
-- Repeat the Check fuel pump delivery pressure/delivery quantity function.
The Transfer Fuel Pump -G6- is now activated for 30 seconds.
-- Check the fuel delivery rate in the measuring container.
Minimum delivery rate specified value: greater than 1.7L/30 seconds.
If the minimum delivery rate is not reached:
-- Check the fuel lines inside the engine compartment for possible bends (kinks), blockages and damage.
-- Check the fuel lines inside the engine compartment for leaks.
If no error can be found:
Check the fuel delivery rate in front of the fuel filter as follows:
Checking the fuel delivery rate in front of the fuel filter:
-- Remove the fuel supply line -1- from the fuel filter.
-- Connect the :VAS6551/2 to the connection -B- from the :VAS6551 .
-- Connect the :VAS6551 with the :VAS6551/2 and the :VAS6551/5-1 to the fuel supply line.
-- Secure the fuel supply line with hose clamps. Ensure proper seating of the hose clamps.
-- Connect the :VAS6551/6 to the connection -B- on the :VAS6551 .
-- Hold the open end of the :VAS6551/6 hose in a measuring container.
-- The shut-off valves -A- and -B- are open on the :VAS6551 -1-.
-- The shut-off valve -C- on the :VAS6551 -1- must be closed.
-- Connect the Vehicle Diagnostic Tester .
-- Select the 0001 activate fuel pump Guided Function.
-- Select the Check fuel pump delivery pressure/delivery quantity function.
-- Follow the instructions on the Vehicle Diagnostic Tester.
-- Set the pressure to 4.0 bar using the :VAS6551/6 .
-- The initial pressure is set by turning the adjusting wheel -arrow- on the :VAS6551/6 .
- Specified value: 4.5 bar pressure.
-- Do not move the adjusting wheel -arrow- anymore.
-- Empty the measuring container.
-- Repeat the Check fuel pump delivery pressure/delivery quantity function.
The Transfer Fuel Pump -G6- is now activated for 30 seconds.
-- Check the fuel delivery rate in the measuring container.
Minimum delivery rate specified value: greater than 1.7L/30 seconds.
If the minimum delivery rate is now reached:
Check the fuel filter and replace it if necessary -step ) OVERVIEW - FUEL FILTER - FUEL FILTER.
If the specified value is not reached again:
Check the fuel delivery rate on the fuel delivery unit as follows:
Fuel Delivery Rate, Checking on Fuel Delivery Unit:
-- Remove the right rear seat or rear bench seat. Refer to REAR SEATS, REMOVING AND INSTALLING .
-- Fold the right carpet cutout to the side.
-- Loosen the nuts -1 through 4- on the flange cover.
-- Remove the flange cover.
-- Disconnect the fuel supply line -2-. Disconnect the connector couplings. Refer to CONNECTOR COUPLINGS, DISCONNECTING .
-- Connect the :VAS6551 with the :VAS6551/5-3 and the :VAS6551/5-4 as shown.
-- Hold the end of the :VAS6551/5-3 in a measuring container -1-.
-- Open the shut-off valves "A" and "B" on the : VAS6551 in the flow direction.
-- Close the shut-off valve "C".
-- Switch the ignition on.
-- Perform the guided function "activate fuel pump".
-- Select the "Check delivery quantity" function.
The fuel pump now runs for 30 seconds.
-- Slowly close the shut-off valve -B- until a counter pressure of 4 bar is achieved.
-- Empty the measuring container.
-- Perform the guided function "activate fuel pump" again.
-- Select the "Check delivery quantity" function.
The fuel pump now runs for 30 seconds.
Minimum delivery rate specified value: greater than 1.7L/30 seconds.
If the specified value is now reached:
-- Check the fuel supply line to the fuel filter for kinks and damage.
If the specified value is not reached again:
-- Replace the fuel delivery unit.
If the Diesel Pressure Tester Kit:VAS6551 is to be removed, open the shut-off valve "C" and reduce the residual pressure. For this purpose, hold the hose from the shut-off valve "C" in a measuring container.