0195 - A. Testing exhaust gas recirculation Engines 601.911/912 up to 01/93, 602, 603

07.1-195 Testing exhaust gas recirculation

A. Engine 601.911/912 up to 01/93,
Engine 602, 603

Function diagram exhaust gas recirculation

1) not applicable on engine 601    code 960 and 830 model year 1991

Special tool

Commercially available tools

Note
Use Y-distributor, part no. 117 078 01 45 for vacuum tester.

Test condition

Coolant temperature 60-80 °C.

Function test

Checking ARF valve (60) with engine switched off
Apply vacuum of approx. 300 mbar to ARF valve. Pull off vacuum line.

ARF valve closes audibly.

ARF valve fails to close.

Renew ARF valve.

End of test

Test vacuum transducer (123) and vacuum setting (only for automatic transmission). Connect vacuum tester with Y distributor to connection "ARF" and read off vacuum level at idling speed.

Specifications in mbar:

Pneumatic pressure control flap up to 1988

32020

35020 only 

Mechanical pressure control flap as of 1989

30020

If the vacuum is above or below specification, adjust vacuum. To do this, remove protective cap (124) and adjust with socket wrench insert (4 mm) to specified value.

Settings in mbar:

Pneumatic pressure control flap up to 1988

3205
 3505
 as of model year 1986 must no longer be ajusted

Mechanical pressure control flap as of 1989 engine 601.91, 602.91

3005

Engine 603.91

3505

Check supply vacuum on connection "VAC", renew vacuum transducer if required. Check vacuum lines according to function diagram.
Check supply vacuum on vacuum pump (07.1-160).

Set value: > 700 mbar

End of test

Checking vacuum control
Connect vacuum tester with Y-distributor to ARF valve (60). Check vacuum values and position of vacuum unit (100) and vacuum control flap.

Test values in order.

Test values not in order.

Vacuum ok

Vacuum not ok

Check vacuum supply and individual parts.

End of test

Function in order.

Function not in order.

Check individual parts.

Checking microswitch (S27/6, I + II)
Connect vacuum tester with Y-distributor to EGR valve (60).

Run engine at 100050/min.

Actuate microswitch (S27/6 I), the vacuum on the ARF valve (60) drops to 0 mbar. The vacuum control flap (in the air guide housing) returns to basic position.

Actuate microswitch (S27/6 II), the vacuum control flap (100) returns to basic position.

Piston rod of vacuum unit retracted - vacuum control flap closed (arrow).

Testing components

-------------------------------

Remove ARF valve and apply vacuum of approx. 300 mbar with vacuum tester.

ARF valve lifts approx. 4 or 6 mm off the seat (end stop  arrow).

Pull off vacuum line, the ARF valve should close audibly.

If one of these test steps is not successful, renew ARF valve.

Checking ARF valve (60) with engine switched off
Apply vacuum of approx. 300 mbar to ARF valve. Pull off vacuum line.

ARF valve closes audibly.

ARF valve fails to close.

A open

B closed

End of test

Check vacuum lines according to function diagram.

Check supply vacuum at vacuum pump.

Set value: > 700 mbar
Adjust vacuum control valve (65)
(07.1-170).

End of test

Checking vacuum control valve (65)

A. Automatic transmission:
Connect vacuum tester with Y-distributor to "VCV" connection of vacuum transducer (123) and check vacuum at idle speed.

Set values:
At idle speed > 300 mbar
With engine switched off and control linkage in full load stop position 0 mbar.

B. Manual transmission: (except USA)
Connect vacuum tester with Y-distributor to connection "A" of change-over valve (Y27) and check vacuum.

Set values:
At idle speed > 300 mbar
With engine switched off and control linkage in full-load stop position 0 - 250 mbar.

Test values in order.

Test values not in order.

Checking change-over valves (Y27 and Y28)
Connect voltmeter to connector of change-over valve and read voltage at 100050/min.

Set value: approx. 12 V.

Voltage in order.

Voltage not in order.

End of test

Check electrical actuation according to wiring diagram, renew ARF control unit (N37 or N37/2) if required.

Connect vacuum tester with Y-distributor to connection "C" and check vacuum at 1000 or 120050/min, a voltage of 12 V is present.

Engine 601.911/912, 602  up to model year 1985

Change-over valve (Y27) 35020 mbar

Change-over valve (Y28) > 700 mbar

Engines 601.9, 602, 603     

at 100050/min, a voltage of 12 V is present.

Change-over valve (Y27) 250 - 400 mbar

Change-over valve (Y28) 250 - 400 mbar

From model year 1990 check engines with

mechanical actuation of the pressure control

flap at 100050/min, applying 12V.

Change-over valve (Y27) 350 - 400 mbar

Change-over valve (Y28) > 700 mbar

Check supply vacuum at the vacuum pump (07.1-160).
Set value > 700 mbar.

Check vacuum lines according to function diagram.

End of test

Engines with mechanical actuation of vacuum control flap as of model year 1990.

Check vacuum at the straight connection of the thermovalve (180) and supply vacuum to the vacuum pump.

Set value: > 700 mbar

Check vacuum line in accordance with the functional diagram, renew thermovalve (180).

Vacuum value not in order.

Vacuum value in order.

1) Measured at 20 °C ambient temperature. (The resistance changes by 4% for each 10 °C change in ambient temperature).

Checking speed signal

Remove plug connector (L3X). Connect multimeter and press button "V". Allow engine to idle.

Display: > 1.5 V

Voltage rises with increasing speed.

In order.

Not in order.

End of test

Remove starter ring gear speed sensor (L3).
Connect multimeter as above and press key

"W". Check resistance.

In order.

Not in order.

Renew starter ring gear speed sensor (L3).

End of test

Display: "Beru" 530 1) W 10%

"VDO" 1900 1) W 10%

Inspect starter ring gear speed sensor (L3) for accumulation of dirt or metal chips, clean if required.

Checking activation of temperature

switches

(S25/9) 97 °C Engine 602

Engine 603

(S25/1) 100 °C Engine 601

Function in order, renew temperature switch.

Function not in order

Check electrical activation, renew ARF control unit (N37 or N37/2) if required.

End of test

Connect vacuum tester with Y-distributor to

ARF valve.

Run engine at 1000/min. Pull plug off

temperature switch (S25/1) and bridge, except

1-pole version of temperature switch (S25/1),

hold the plug against ground (electronic clutch

should be heard to attract).

Vacuum 0 mbar on ARF valve.

Checking activation of 25 °C temperature

switch (S25/7)

Function in order.

Function not in order.

Check electrical activation, renew ARF control unit (N37 or N37/2) if required.

End of test

Connect vacuum tester with Y-distributor to ARF valve.
Engine temperature > 25 °C
Run engine at 1000/min, pull plug off

temperature switch and hold against ground.

Vacuum 0 mbar on ARF valve.

Checking microswitch (S27/6 I and II)

Engine switched off. Pull coupling off

microswitch (S27/6) and check with ohmmeter

for continuity on plug 2 and 4 and 1 and 3.

At idle speed: 0 W

At full load:  W

Display in order.

Display not in order.

Renew microswitch (S27/6).

End of test.

Checking full-load contact on microswitch (S27/6 I)

Display in order.

Display not in order.

Renew microswitch (S27/6).

End of test.

Engine switched off. Coupling pulled off

microswitch (S27/6). With ohmmeter check

continuity on plug 1 and 5.

At idle speed:  W

At full throttle: 0 W

Vehicles with manual transmission in model 201.122 with engine 601.921 

Check electrical activation of change-over valve (Y27). Connect multimeter to plug (arrow) of change-over valve (Y27) and again test- drive.

If voltage (approx. 12 V) is available at a speed > 788 km/h, check electrical activation of change-over valve (Y27) according to wiring diagram.
Renew defective parts if required.

If no voltage is present, renew change-over valve (Y27).

End of test.

Checking speed shut-off

Connect vacuum tester with Y-distributor to ARF valve. Run vehicle on test stand or road in the 5th gear under part load.

Read off vacuum.

Display

speed

< 788 km/h: approx. 300 mbar

> 788 km/h: approx. 0 mbar

Vacuum values in order.

Vacuum values not in order.