Measuring Fuel Pressure EMS 2000

Measuring fuel pressure EMS 2000

Removal





Remove
- The cover over the throttle pulley.
- The aluminium plate, (on turbocharged engines).
- The protective cap on the Schrader valve.

Checking the vacuum system




Disconnect the vacuum hose from the pressure regulator and the intake pipe.
Check that the vacuum hose is undamaged and not clogged.
Replace the front pressure regulator if there is fuel in the vacuum hose.
Check the vacuum hose nipple on the intake pipe, clean if necessary.
Continue with "Connect the test equipment" (3).

Connect the test equipment




Assemble 999-5011 and 998-9725 with J-41031-A
Avoid fuel spillage.
Connect the open end of the hose from the fuel gauge to the fuel draining unit.

Warning! Secure the hose onto the fuel draining unit to prevent fuel leakage

Screw nipple J-41031-A into place on the Schrader valve.
Hang the gauge on the hood catch or the safety catches.
Turn the cock to position (1).

Fuel pressure measurement





Note! Note the measurement value at this step.The result might be needed as a reference in step 12.

Disconnect the vacuum hose from the pressure regulator.

Note! Position the gauge so that the movement of the needle can be read when the engine is started.

Start the engine.
The pressure should rise to approximately 309 kPa (45psi) immediately.
If the pressure is correct, continue measuring the "Front pressure regulator" (5) or (6).
A:The pressure rises slowly to the correct pressure:
Switch off the engine.
Continue with " Check the rear fuel pressure" (8).
B:Too low or too high pressure.
Switch off the engine.
Continue with " Check the rear fuel pressure" (8).

Front pressure regulator, B4XX4T





Caution! When applying vacuum or pressure to the regulator, do not exceed the pressure values stated.Damage to the diaphragm in the regulator may occur.

Connect pump 999 5757 to the regulator.
Pump up a vacuum.
The pressure reading should go down.
Fuel pressure must not be lowered below 240 kPa.
Release the vacuum.
The pressure should rise to approximately 309 kPa immediately.
Pump up the pressure.
The pressure reading should go up.
Fuel pressure must not be raised above 380 kPa
Release the pressure.
The pressure should return to approximately 309 kPa immediately.
Continue with "Check the residual pressure"(7).
If the pressure regulator is not functioning correctly, replace the front pressure regulator.

Checking the residual pressure




The starting pressure is 309 kPa
Switch off the engine.
Note the time.
The fuel pressure must not be lower than 200 kPa for 20 minutes.

Hint: Too low residual pressure can be caused by leakage in the injectors, the check valve in the fuel pump or leakage in the pressure regulators.

Remove the test equipment from the car. Return the equipment to the tool board.
Reinstall the removed components and the cap on the Schrader valve.






Note! The rear fuel pressure measurement test must only be carried out if the result of step 4 is in accordance with A or B.

Raise the car.
Remove the guard.





Warning! The fuel filter must not hang from the fuel lines during this test. Secure the fuel filter using tie straps.

Slacken off and open the clamp for the fuel filter (1)
Carefully work the filter downwards.
Remove the cap on the Schrader valve.
Screw nipple J-41031-A (2) into place on the Schrader valve, see 3.





Note! Hang the pressure gauge so that the value can be read off easily when the car has been lowered.

Lower the car.

Starting the fuel pump (FP)




Remove relay 2/14.
Make up a bridging cable.
Bridge terminals 30 and 87. The fuel pump (FP) starts.

Rear fuel pressure




The pressure must rise to approximately 430 kPa immediately.
If the rear fuel pressure is incorrect, replace the rear pressure regulator which is integrated in the fuel pump (FP).
If the rear fuel pressure is correct and the fuel pressure is incorrect in step 4, select the fault tracing path. See note below.
A:The rear fuel pressure is normal but in step 4 rose slowly to appr. 309 kPa. Check if the fuel line is damaged or pinched. If the fuel line is intact, replace the fuel filter.
The fault is remedied.
B:The rear fuel pressure is normal but in step 4 the pressure immedatly rose to a too low/high value. Replace the front pressure regulator.
The fault is remedied.
Disconnect the test equipment.
Reinstall the components in reverse order.