Engine Hesitates, Cuts Out, Hard Start

07.3-87041 Engine Hesitates, Cuts-Out or is Difficult to All Models with CIS-E Revised 4/90 4/87
Start at Times Injection System

Cause/Remedy:
In case of complaints regarding the engine cutting out which may be intermittent, or in cases where the engine cuts out and can be started again after a short period of time the following points should be checked:

Note:
Misadjustment of the transmission control pressure cable may be diagnosed as hesitation. Make sure the cable is adjusted to specification.

Engines 102.983,103.983 and 116/117 as of MY 1986 and engine 102.985 as of MY 1987 with EZL electronic ignition system.

- Check the crankshaft position sensor. If the production date on the sensor is below 642 (e.g. 640, 635), the sensor with the attached cable should be replaced with one of a later production date. If the production date of the sensor is 642 or later, test the sensor and cable assembly for an intermittent interruption, short to ground, and resistance. Nominal value 680 - 1200 Ohms (at room temperature). Replace if necessary.

- Check ignition timing (EZL system).

- Check electrical connections on ignition coil.

- Check sockets in plugs of fuel pump relay and overvoltage protection relay for good solder connections and tight fit on pins with gauge or jumper wire from electrical Connection Kit, 201 589 00 99 00, they must not be spread apart.

All gasoline engines with rpm controlled fuel pump relay (Including those listed above)

- The engine rpm signal (circuit TD) to the fuel pump relay may be short-circuited to ground or otherwise disturbed by one of the following components which utilize this signal:

A/C compressor control unit
CIS-E control unit
Idle speed control unit (engines 116/117 only)
Tachometer

Note:
The ignition control unit is the source of the TD signal. If the wiring leading away from this unit is defective (i.e. short to ground, open circuit) any or all of the components listed above may be affected.

- Fuel pump relay and A/C compressor control unit may become defective because of corrosion. Moisture can enter the relay via the vent bore in the plastic locating pin on the relay. Belays of later production do not have this vent hole. Before installing a replacement relay, check whether this vent bore is closed. If not, close this bore in the plastic locating pin with an adhesive (RTV or similar). On model 124 vehicles with serial end number below A 314253, the modified cover panel for the electronic components, part no. 124 626 16 30 and the cover panel on the crossmember, part no. 124 620 30 67, can be installed.

- A defective tachometer can be diagnosed by disconnecting the plug on the tachometer. If this eliminates the engine cut-Out problem, replace the tachometer.

Model 201.024 with engine 102.985, Model Year 1985/1986

- Engine misses or cuts out when horn is actuated. Replace ignition control module.

- Connector for circuit 30 on electrical center is loose. Tighten MG terminal screw (circuit 30) on face of electrical center in engine compartment to 5 Nm.

Engine 103.983, Model Year 1986 only

- The ignition spark jumps to ground inside the ignition distributor as a result of the carbon contact in the distributor cap missing, or bore for carbon contact in distributor cap is burned Out. Remove distributor rotor. If burn marks are visible on the back side of the flange, replace rotor. Replace distributor cap.

Engine 102, 103

- Loose electrical connection in plug of coolant temperature sensor. The CIS-E control unit switches to the fixed operation mode only when an interruption is detected, not with a loose (intermittent) connection. Replace plug on coolant temperature sensor, part no.013 545 87 28.

Engine 103

- Hesitation after cold start - Install CIS-E control unit with Bosch production date 848 or later. Production Phase-In: August 1988

Further possible causes (CIS-E related)

- Loose ground terminal screw at Intake manifold.

- Loose connectors for CIS-E wiring harness.

- Loose connector (ground) in trunk for fuel pump.

- Loose connection at plug (X36) of fuel pump wiring harness.

Damage Code:
54481 73