Fuel System Pressure and Internal Leakage Test

Fuel Pressures:

FUEL SYSTEM PRESSURES

VISUAL INSPECTION
1. Remove air cleaner.
2. Check all fuel connections for leaks.
3. Check air flow sensor for proper movement and smooth operation.
4. Check fuel distributor plunger piston for signs of leakage.

Fuel Pressure Gauge:

FUEL PRESSURE GAUGES

Lower Chamber Plug:

LOWER CHAMBER PRESSURE PLUG

Fuel Gauge Connection:

FUEL GAUGE CONNECTION

PRESSURE GAUGE CONNECTION
If using factory gauge version 1 (PN 11004 6449/1):
1. Connect hose #1 to fuel distributor lower chamber.
2. Connect hose #2 to pressure gauge.
3. Connect hose #3 to fuel distributor upper chamber (cold start valve connector).

If using factory gauge version 2 (PN 11004 9447/1):
1. Connect hose "A" to fuel distributor lower chamber.
2. Connect hose "B" to fuel distributor upper chamber (cold start valve connector).

To use any other gauge, refer to the manufacturer's instructions.

Fuel Pump Relay Bypass:

ACTIVATE FUEL PUMP
1. Turn ignition OFF.
2. Remove the fuel pump relay (in relay compartment) and bridge number 7 and 8 connectors at the harness.
3. Turn ignition ON.

CHECK SYSTEM PRESSURE
Version 1:
Close valve screw connection 1
Open valve screw connection 3

Version 2:
Open valve screw

Nominal gauge pressure should be:

Engine 102.96/98 5.3-5.5 bar
Engine 102.983 5.7-5.9 bar

If gauge pressure is incorrect, check:
Fuel pump
Fuel pressure regulator
Fuel return and supply lines

CHECK LOWER CHAMBER PRESSURE
Version 1:
Open valve screw connection 1
Close valve screw connection 3

Version 2:
Close valve screw

1. Disconnect electrical connector from electro-hydraulic actuator.
2. Note gauge pressure. Nominal gauge pressure should be:

0.4 bar below system pressure

3. Reconnect electrical connector to electro-hydraulic actuator. Pressure should remain stable.

If gauge pressure is incorrect, check:
Temperature sensor
Control Unit
Electro-hydraulic actuator
Fuel distributor throttle orifice

Turn ignition OFF. Remove jumper wire from fuel pump relay connector. Re-install fuel pump relay.

CHECK DECEL SHUTOFF
1. Start engine and warm up to operating temperature.
2. Raise engine speed to 2,500 RPM, then release throttle.
3. When engine speed drops, lower chamber pressure should increase to system pressure.

If lower chamber pressure does not increase, check:
Micro-switch
Actuator control current
Control unit
TD signal

Micro-switch:

MICRO-SWITCH

Micro-switch Bridge:

JUMPER

CHECK FULL LOAD ENRICHMENT
1. Disconnect micro-switch connector and bridge contacts with jumper wire.
2. Increase engine speed to 1,500 RPM.
3. Note gauge pressure. Lower chamber pressure should drop by:

0.05 bar

If gauge pressure is incorrect, check:
Throttle valve switch
Actuator control current
Control unit
TD signal

Temperature Sensor Resistor:

CHECK ACCELERATION ENRICHMENT
1. Disconnect temperature sensor wire from sensor. Connect wire between a 2.5k Ohm resistor and ground.
2. Race engine several times between idle and 2,500 RPM.
3. Lower chamber pressure should drop as RPM increases.

If gauge pressure does not drop, check:
Air flow sensor transmitter
Actuator control current
Control unit

CHECK RESIDUAL PRESSURE
1. Turn ignition OFF.
2. System pressure should remain at:

2.8 bar (approx.)

If fuel pressure drops immediately to 0, replace fuel pump check valve.
If fuel pressure drops slowly, check:
Fuel pressure regulator
Fuel return line
Fuel reservoir

END OF TEST
1. Disconnect fuel gauge.
2. Refit all fuel lines and electrical connectors.
3. Start engine and re-check for leaks.