M110,  Mechanical gazoline injection system CIS

Checking choke system



07.3-125 Checking choke system


Test values in bar gauge pressure


110.984/985 110.986/987
110.988/989 110.990
System pressure at idle with engine cold or at operating temperature
Warm-up compen­sator stabilized
3.4-3.8 at 530 mbar ‘)
Control pressure at idle with „….., Full load ennch-engme at operating temperature mentatidle
(vacuum hose pulled of)


Control pressure according to ambient temperature at idle with engine cold
min. 0.5
(refer to diagram)


Starting voltage
10 V


) If the control pressure is not attained, check intake manifold vacuum (section “Checking control pressure at idle with engine at operating temperature”).


Special tool


Pressure measuring device
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102 589 00 21 00


Conventional tools


Voltmeter and ohmmeter


Revolution counter




1 Pull cable plug from warm-up compensator and from cold starting valve.


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2   Checking starting voltage.
Pull plug from ignition transmitter on switching unit (green cable) or plug protective plug, part no. 102 589 02 21 00, on diagnosis socket.
Operate starter for a short moment while reading voltage. Nominal value min. 10 Volts. If nominal value is not attained, test battery, charge or replace, if required.
3   Check air flow sensor plate and control piston for easy operation, check fuel pressures and for internal leaks, as well as stabilizing time of warm-up compen­sator (07.3-120).
Checking cold-starting valve for function and leaks
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4   Unscrew fuel line on cold-starting valve (98) and remove cold-starting valve.
5   Loosen fuel line (arrow) on fuel distributor and turn in such a manner that the cold starting valve can be again connected. Then hold cold starting valve into a container.


Checking function
6   Switch-on ignition.
7   Connect cold starting valve with separate cable to B + and ground. Cold starting valve should eject in shape of cone.
Connect cable first to cold starting valve so that no sparking occurs.
No separate cable need be used below +15 °C, plug-on cable plug instead and pull cable plug from safety switch.


Checking for leaks
8   Loosen separate cable connection on cold starting valve. Dry cold starting valve on nozzle. No drops should form.
9   Switch off ignition.
10   Mount cold starting valve with new seal.
11    Plug cable plug on safety switch and on cold-starting valve again.


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Testing thermo time switch
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The cold starting valve is actuated by closed thermo time switch only at coolant temperatures below + 15°C.
The actuating time increases with decreasing tempera­ture and attains approx. 12 seconds at —20 °C.
99 Thermo time switch


Testing below +15 °C coolant temperature


12   Connect voltmeter to connection of cold starting valve.
13    Actuate starter. Depending on coolant tempera­ture, voltmeter should then indicate 10 Volts for a given period.
The switching time increases with decreasing tempera­ture by approx. 1.5 seconds per 5 °C.
e.g. + 15 °C =0 seconds + 10 °C= 1.5 seconds
It is recommended to test thermo time switch additionally with an ohmmeter for this test.
Test value below+15 °C:
Connection G-ground = approx. 48 12 Connection W-ground = approx. 012
(Contacts in switch closed).


Testing above +15 °C coolant temperature


Above +15 °C coolant temperature the thermo time switch can be tested only by means of an ohmmeter. For this purpose, pull plug from thermo time switch.
Test values above +15 °C:
Connection G-ground = approx. 62 12 Connection W-ground = approx. 270 12
(Contacts in switch open). Re-attach plug.
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98  Cold starting valve
99  Thermo time switch c To terminal 50





Testing cutoff point of auxiliary air valve


14    Following a cold start, the engine speed should amount to approx. 800—1000/min. The speed will then increase to approx. 1 200—1300/min, and will drop to normal idle speed at approx. 70 °C.
15   Stop engine. Disconnect pressure measuring device while catching fuel with a rag.
16   Connect fuel lines, run engine once again and check all fuel connections for leaks.


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