Fuel Pump, Checking: Notes
Special tools and workshop equipment required
- Hand held remote control (jumper).
- Multimeter.
- Voltage tester
- Measuring container
- Wiring diagram
Test conditions
- Read safety precautions before beginning work.
- Maintain clean working conditions.
- Battery voltage at least 12.5 V
- Fuse for Fuel Pump (FP) OK.
- Fuel Pump (FP) Control Module -J538- OK.
- Low Fuel Pressure Sensor -G410- OK.
Test procedure
-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .
Function and Voltage Supply, Checking
-- Switch ignition on. Fuel pump must run audibly for approx. 2 Seconds.
-- Switch off ignition.
If Fuel Pump (FP) does not start up:
-- Remove nuts -1- on right side of fuel delivery unit cover. If necessary, remove backrest support -2- or mounting bracket:
-- Disconnect connector from Fuel Pump (FP) Control Module -J538- -5-.
-- Switch ignition on.
-- Check voltage supply between connector terminals -3- and -4- using low voltage tester. LED must light up.
-- Switch off ignition.
LED does not light up:
-- Locate and repair open circuit.
LED lights up (voltage supply OK):
Fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully pulling hose off connection.
-- Remove high pressure in fuel system.
-- Remove fuel supply line -1-, auxiliary heater fuel line -2-, fuel pump connector -3- and vent line -4-.
Press in securing ring to disengage the fuel line.
-- Open locking ring using wrench T10202.
-- Check whether electrical wires between flange and Fuel Pump (FP) are connected.
If no open circuits are found:
-- Fuel Pump (FP) faulty, replace fuel delivery unit.
-- 4.2 Liter V8 4V Engine Mechanical, Fuel Injection & Ignition, Engine Code(s):
Fuel Pressure, Checking
-- Remove high pressure in fuel system.
Fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully loosening the union nut.
-- Place a cloth around connection and loosen union nut -arrow- to reduce fuel pressure.
-- Then tighten threaded connection again.
-- Connect a Pressure Tester with Adapter, as shown.
-- Make sure hose clamps are seated securely.
-- Open shut-off valve of pressure gauge set. The lever points in the direction of flow.
-- Remove nuts -1- on right side of fuel delivery unit cover. If necessary, remove backrest support -2- or mounting bracket:
-- Disconnect connector from Fuel Pump (FP) Control Module -J538- -5-.
-- Disconnect harness connector -3- from flange of fuel delivery unit.
-- Connect Hand held remote starter (jumper) with adapter cables from connector test kit to terminal -1(+)- of Fuel Pump (FP) and to terminal -3(+)- of harness connector of Fuel Pump (FP) Control Module -J538-.
-- Connect terminals -4(-)- of harness connector and -4(-)- of Fuel Pump (FP) using an adapter cable from connector test kit.
-- Switch ignition on.
-- Operate Hand held remote starter (jumper) and observe display of pressure tester while doing this.
Fuel pressure must increase up to a maximum pressure of 6 bar.
When releasing control button of remote control, fuel pressure decreases to approx. 5.6 bar.
If fuel pressure is OK, check Residual Pressure FUEL PUMP, CHECKING .
If specification is exceeded:
-- Pressure relief valve in sensor flange faulty, replace sensor flange.
If specification is not obtained:
-- Check fuel lines for possible restrictions (kinks) or blockages.
-- Check all fuel lines in fuel tank for leaks.
-- Check fuel filter for leaks.
If no malfunction can be found:
-- Replace sensor flange with pressure relief valve.
-- Repeat test.
If fuel pressure is not obtained again:
-- Fuel Pump (FP) faulty, replace fuel delivery unit.