Info

Note:

The fuel pump can be run by connecting battery on terminal 4 of the 9-pin plug.

Alternator, regulator Intake system leaks

Throttle bypass valve

CO and idle speed adjustment

Cold start enrichment

Throttle switch

Temperature sensor II (engine temperature)

Fuel injectors, injection timing

Fuel pressure Air flow sensor Ignition system Reference mark transm.

Speed transmitter

Power supply for control unit/fuel pump

Ground connections, plug connections

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The test points should be performed in the given sequence, especially when the customer complaint concerns an engine which cannot be started or is hard to start.

3. Check plug connections listed below carefully for tight fit, bent plug sleeves and corrosion.

TEST POINT 1

Checking Ground and Plug Connections

1. Check both ground connections next to pulse transmitters for cleanliness and firm contact.

2. Check ground connection between engine and body.

3.1 Plug connection for DME control unit.

To remove, push catch toward right side and at same time take off plug forward.

3.2 Plug connection for speed and reference mark transmitters (check codes).

3.3 Plug connection for air flow sensor.

3.6 Plug connection for fuel injectors.

3.4 Plug connection for throttle switch.

3.7 Plug connection above brake booster.

3.5 Plug connection for temperature sensor II (engine temperature).

3.8 Relay socket of fuel pump relay.

Note:

Frequent removal and installation of the relay could loosen and push back the catch for flat female plugs.

TEST POINT 2

Power Supply for DME Control 2. F u e I Pump

Unit and Fuel Pump

1.DME Control Unit

1.1 Turn off ignition and pull off multiple pin plug on DME control unit.

1.2 Turn on ignition.

1.3 Measure voltage between term. 35 and term. 5 as well as between term. 18 and term. 5.

Check the following points, if for example the fuel pump does not run while starting the engine.

2.1 Check fuse 2(16 amps) in auxiliary fuse box.

2.2 Check fuel pump relay.

2.3 Supply battery voltage to term. 4 of 9-pin plug connection above brake booster, or bridge term. 30 and 87 b on socket of fuel pump relay.

Fuel pump should then run.

// 35 34333231 30 29 28 27 26 25 24 23 22 21 20 ill

TEST POINT 3

Note:

An oscilloscope should be used to check the speed and reference mark transmitters.

Specification: battery voltage.

(Always use extra wires to connect tester.)

If voltage deviates from specified value, check fuel pump relay, 9-pin plug connection above brake booster (term. 2 and term. 3) and corresponding wires.

Speed Transmitter

1. Turn off ignition and pull off multiple pin plug on DME control unit.

2. Connect and adjust oscilloscope.

1.4 Turn off ignition and connect multiple pin plug on DME control unit.

SUN 1010

Cylinder selector switch set to 2

Engine cylinder switch set to 4-stroke

Voltage selector switch for image screen scale set to 50 V

Ignition coil polarity switch set to +

Image selector switch set to parade

SUN 1080

to 2

Image selector switch superimposed or set to parade; program switch set to pos. 2 to 5 ( n e v e r to 1)

BOSCH MOT 002.01

Range selector switch set to "special" pos.

Special wire connected on test terminals off DME control unit with help of auxiliary wire

Screen control lever moved against left stop

Connect blue connection via locally made auxiliary wire on term. 8 and black connection on term. 27 of DME plug.

If the transmitter signal is less than 2.5 V, check distance between starter gear ring and transmitter.

Specification: 0.8 ± 0.05 mm (see page 28 -14 in Repair Manual).

3. Start engine.

Sine oscillation, the amplitude of which must be more than 2.5 V from peak to peak, must be displayed on the screen.

If a transmitter signal is not displayed in spite of correct connection and correct adjustment of tester, measure power flow and insulation of speed transmitter.

U>2,5V

Coil resistance term. 8 against term. 27. Specification: 0.6 to 1.6 k-ohm.

Insulation resistance term. 8 against term. 5. Specification: more than 1 M-ohm.

Replace speed transmitter, if necessary.

TEST POINT 4

Reference Mark Transmitter

Adjust oscilloscope as described in point 3.

(If using SUN 1080, press one of "ignition coil test buttons for a better picture.)

If there is no transmitter signal, proceed as described in test point 3 for speed transmitter. The same specifications are applicable.

Connect blue connection via locally made wire on term. 25 and black connection on term. 26 of DME plug.

If using Bosch tester, connect red clip of special lead on term. 25.

Start Engine

A single sine oscillation should be displayed on the screen. It is important that the oscillation begins with a positive slope and more than 2 V is displayed on the screen scale with a starter speed of at least 200 rpm (the signal amplitude depends on the starter speed).

If the transmitter signal is less than 2 V, check distance between transmitter and reference mark.

Specification: 0.8 ± 0.05 mm (see page 28 -14 in Repair Manual).

TEST POINT 5 Ignition System

1. Adjust secondary image on oscilloscope: term. 1 and term. 15, trigger clip on cylinder no. 1.

Note:

If a defect is displayed for all cylinders, it will be in the primary or secondary circuit from the ignition coil to the distributor rotor. If a defect is displayed for only one cylinder, it will be after the distributor rotor.

2. Check distributor cap for damage, burnt spots and dirt.

Retaining hooks must engage firmly when installing.

3. Check distributor rotor. Shielded resistance: 1 k-ohm. Check visually for tight fit, damage and dirt.

4. Check spark plug caps and leads for damage or traces of burning. Shielded resistance: 3 k-ohm.

5. Check ignition coil. Primary resistance:

Secondary resistance:

Check visually for damage or burnt spots. Note:

Avoid checking the ignition system via the spark gap by pulling off the spark plug caps. This could cause destruction of the ignition coil and control unit.

6. Check ignition timing at idle speed and with engine having operating temperature.

Ignition timing at 800 + 50 rpm = 5 to 15° before TDC.

TEST POINT 6

Air Flow Sensor

1. Push back protective sleeve of the air flow sensor connector. The connector remains attached. Connect voltmeter to terminal 9 and to terminal 6 on the rear of the connector.

4. Check temperature sensor I (intake air temperature). Turn off ignition and pull off plug on air flow sensor. Connect ohmmeter between term. 6 and 22 on air flow sensor (both outer flat male plugs).

Note

Interruption on temperature sensor causes richer mixture.

Short on temperature sensor causes leaner mixture.

Specification: more than 8 V.

2. Remove air cleaner.

Connect voltmeter between term. 7 and ground.

Specification: approx. 150 to 250 mV.

3. Push sensor plate to full throttle position with a not-to-hard, smooth item inserted through the filter intake opening.

Voltage rises above 8 V with sensor plate fully open (switch over test range). The sensor plate must not stick and return to off position on its own when released.

TEST POINT 7 Fuel Pressure

1. Open flap on distribution tube.

Unscrew capped nut on test connection.

Note:

Be careful that sealing ball does not fall out when removing the capped nut.

Catch escaping fuel.

Electric sparks could cause fire!

3. Start engine and measure fuel pressure at idle speed.

Specification: approx. 2.0 bar (29 psi).

4. Pull off vacuum hose on pressure regulator. Fuel pressure should rise.

2. Connect pressure tester P 378 on distribution tube.

5. If fuel pressure deviates from specified values, pinch return line shut slowly with a clamp.

Replace pressure regulator if pressure rises above 4 bar (58 psi).

If pressure remains below 4 bar (58 psi), check fuel filter or replace fuel pump.

TEST POINT 8

Fuel Injectors and Injection Timing

1. Checking Fuel Injectors

If engine does not run, supply battery voltage to term. 4 of 9-pin plug or bridge terminals 30 and 87 b on socket of fuel pump relay.

If engine can be run, disconnect plugs on injectors separately.

If injectors are okay, the engine speed will drop each time.

Fuel pump should run.

If engine cannot be run, measure voltage on one plug connection of injectors against ground. One of both terminals must have battery voltage; if necessary perform test point 2.

Measure coil resistance on flat male plugs of fuel injector.

Tightening torque for capped nut: Specification: 2 to 3 ohms.

2. Checking Injection Timing

Adjust oscilloscope as described in test point 3.

Connect adapter lead (Bosch "L-Jetronic", No. 1684 463 093) between one fuel injector and its matching plug.

SUN 1010:

Blue tester lead on red Bosch lead.

Black tester lead on black Bosch lead.

Ignition coil polarity set to — and trigger clip connected on term. 4.

Caution! Never let connections contact ground.

Make following connections if idle speed drops after making above connections or engine stops.

Blue tester lead on black Bosch lead.

Black tester lead not connected on red Bosch lead!

Caution ! Never let connections contact ground.

Special black lead and red Bosch lead not connected.

Tester lead for ignition coil connected on term. 1 and 15 of ignition coil.

Caution! Never let connections contact ground.

SUN 1080:

Green tester lead (15) on red Bosch lead.

Blue tester lead (1) connected on black Bosch lead.

BOSCH:

Special red lead on black Bosch lead.

Start engine. The following oscillographs will be displayed on the oscilloscope when injection timing is correct.

STARTER SPEED

t: = Injection time

IDLE SPEED

ACCELERATION

DECELERATION (coasting)

Refer to test point 10 if injection signal does not switch off while decelerating.

TEST POINT 9

Temperature Sensor II (Engine Temperature)

1. Check plug for tight fit and plug receptacles for cleanliness and contact.

2. Connect ohmmeter between term. 13 on disconnected DME plug and ground.

Specifications for 15 to 30 °C (59 to 86 °F): 1.45 to 3.3 k-ohms

Specifications for 80 °C (176 °F): 280 to 360 ohms

If measured values deviate from specified values, repeat test on temperature sensor itself, replacing temperature sensor if necessary.

Note:

Break on temperature sensor causes richer mixture. Short on temperature sensor causes leaner mixture.

TEST POINT 10 Throttle Switch

1. Connect ohmmeter between term. 2 on DME plug and ground.

Specifications with throttle closed: zero ohm throttle open: infinite ohms

Switching over must take place even when throttle is only slightly open (approx. 1°).

2. Connect ohmmeter between term. 3 of DME plug and ground.

Specification with throttle closed: infinite ohms.

Specification with throttle wide open: zero ohm.

Switching must take place immediately before full throttle.

If switching points are not correct, repeat test direct on throttle switch by connecting ohmmeter term. 18 (ground; center flat plug on throttle switch) and term. 2 or term. 3.

Adjusting Throttle Switch

1. Remove throttle housing.

2. Unscrew throttle switch mounting screws.

3. Hold throttle in closed position. Turn switch until Check Full Throttle Enrichment inner stop is felt. Throttle must not be moved.

4. Tighten switch mounting screws.

Throttle must rest firmly on stop screw.

Checking Coasting Shut-off (Stopping of Injection Signal)

1. Pull off plug on throttle switch.

2. Connect term. 2 (idle contact) and term. 18 on disconnected plug with an auxiliary lead. This will simulate a closed throttle for the DME control unit. (Only use suitable flat plugs on auxiliary lead.)

3. Start engine and increase speed to about

1600 rpm. Engine should begin to surge, i. e. the injection signal will be stopped above 1600 rpm.

1. Start engine and run at idle speed.

2. Connect term. 3 (full throttle contact) and term. 18 on disconnected plug. Engine speed should drop.

TEST POINT 11

Cold Start Enrichment

Connect and adjust oscilloscope as described in test point 8 (injection timing).

Start Engine

The signal displayed on the oscilloscope must be spread, but return immediately to the idle signal.

Note:

The spread signal will be very significant and only visible briefly while starting the engine.

ENRICHMENT

IDLE

TEST POINT 12 TEST POINT 14

Leaks in Intake System

CO and idle speed adjustments (see Repair Manual 1. Check all hoses and connections after air from page 25 - 7 on). flow sensor for tight fit and leaks.

2. Tighten hose clamps.

TEST POINT 13

TEST POINT 13

2. Pull off plug on auxiliary air regulator and measure voltage between both plug receptacles. Plug must have battery voltage.

Peak voltage of the alternator could trigger off engine misfiring.

1. Remove drive belt and alternator.

2. Start engine. If defect is eliminated, check alternator and regulator.

Specification: 30 to 65 ohms

3. Measure resistance on auxiliary air regulator with an ohmmeter.

TESTING LAMBDA SENSOR OPERATION

(Short test) Prerequisites:

- Engine at operating temperature

- Idle speed correctly set

1.Connect exhaust tester at bleed nozzle in engine compartment.

3.Pull off negative pressure line from fuel pressure regulator and close with suitable plug.

- Idle speed correctly set

The CO value should rise signifi-. cantly.

4.Reconnect plug on lambda sensor. The CO value should adjust itself to the control value of 0.6 + 0.2%,

2.Detach lambda sensor plug connection, wait for thermal equilibrium, and no CO value.

The CO value should rise signifi-. cantly.

4.Reconnect plug on lambda sensor. The CO value should adjust itself to the control value of 0.6 + 0.2%,

If there is no change in the CO level, there is a defect in the lambda sensor or in the DEE control unit.

Printed in Germany-XV, 1987 Testing Lambda Sensor Operation 28 - 37

TESTING DEE CONTROL UNIT TESTING LAMBDA SENSOR

(Lamba Control Function) (Sensor Voltage)

l.Same prerequisites as for ¡.Prerequisites as for "Testing "Testing Lambda Sensor Operation". Lambda Sensor Operation".

2.Disconnect lambda sensor plug. Briefly connect term. 1 on the plug half to the control unit to ground with an auxiliary lead.

2.Disconnect lambda sensor plug.

3.Clip voltmeter to term. 1 (plug half to sensor) and to ground.

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