Fuel Delivery, Checking

Special tools and workshop equipment required 

• Hand held remote control (jumper).
• Multimeter.
• Electrical connector test lead set.
• Fuel pressure test set (high pressure).
• Measuring container, fuel-resistant.

Test conditions 

• Battery voltage 12.5 V
• Fuel filter OK
• Fuel tank at least ¹ /₄ filled.
• Fuel pressure regulator OK.
• Ignition switched off.

Test procedure 

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .

Start diagnosis 

-- Remove the fuel filler cap from fuel filler tube.

-- Remove rear seat bench. Refer to Rear Seats .

-- Remove cover retainers -arrows- from the right sealing flange.

-- Disconnect the electrical harness connector -arrow- from the fuel delivery unit.

-- Open cover of relay and fuse panel in the engine compartment E-box.

-- Remove fuse SB-7 from fuse holder

-- Connect hand held remote control (jumper) to the left terminal (in direction of travel) of fuse socket. -arrow-.

-- Using insulating tape, tape over second contact of hand held remote control (jumper) to prevent a short circuit.

-- Connect alligator clip to vehicle battery B+.

-- Disconnect return line -1- from fuel pressure regulator.

-- Connect adapter hose to fuel pressure regulator and hold end of adapter in a measuring container.

-- Run hand held remote control (jumper) approximately 5 seconds to fill the fuel filter.

-- Empty measuring container.

-- Delivery rate of Fuel Pump is dependent on voltage. Therefore connect multimeter to battery.

-- Operate remote control for 30 seconds and measure battery voltage.

-- Compare the quantity of fuel delivered with specification.

* Minimum delivery rate cm³ /30 s

** Voltage at fuel pump with engine off and pump running (approx. 2 Volts less than battery voltage).

Example: 

During test, a voltage of 12.5 volts is measured at the battery. Since the voltage at the pump is approx. 2 Volts less than battery voltage, there is a minimum delivery rate of approx. 580 cm³ /30 s.

If the minimum delivery rate is not attained:

-- Check the supply line to filter for possible restrictions (kinks) or clogging.

If fuel line is OK.

-- Check fuel delivery rate in front of fuel filter.

-- Disconnect the supply line from fuel filter input.

-- Connect a Fuel pressure test set (high pressure) as shown.

-- Connect an adapter hose to the Fuel pressure test set (high pressure) and hold it in a measuring container.

-- Open shut off valve of Fuel pressure test set (high pressure). Lever will point in direction of flow.

-- Operate hand held remote control (jumper). Slowly close shut off tap, until pressure gauge shows 4 bar. From this point on do not move position of shut off tap.

-- Empty the measuring container.

-- Operate hand held remote control (jumper) for 30 seconds. Compare delivery quantity with value determined from the first measurement.

If minimum delivery rate is now obtained:

-- Replace fuel filter.

If minimum delivery rate is again not obtained:

-- Remove fuel delivery unit and check filter strainer for dirt.

If the fuel filter and fuel strainer are OK: 

-- Replace fuel delivery unit.

Assembly is performed in reverse order of removal.

Final procedures 

After repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .