46b. D-Jetronic-Trouble Shooting
bron: http://www.geocities.com/MotorCity/Shop/4123/Guzzler.html
Contents:
Starting Trouble
- Engine does not start - Cold engine does not start - Hot engine does not start - Engine starts but stops again after a short time
Idling Trouble - Rough idle during warm-up - Hunting (surging) at idle at all temperatures - Hot engine stalls at idle - Rough idle in driving range (Automatic Transmission) - Idle irregular (like misfiring) - Idle too high
Hesitation Trouble
Poor output, top speed too slow
Fuel consumption too high
Engine misfiring - Misfiring only when electrical components are switched on - Misfiring at all times
CO value too high
Wiring diagrams Type 3 - Up to July 1971 - After August 1971 - After August 1972
Type 4 - Up to July 1971 - After August 1971 - After August 1971 (additional diagram)
Vacuum hose diagrams - Type 3 - Type 4
Engine does not start
See Hot engine does not start - Cold engine does not start
Cold engine does not start Test condition:
- Fuel in tank
A. Incorrect starting procedure Try to start engine using correct procedure (in condition complaint was made) Starting engine: - Gear shift lever in neutral - Do not press accelerator pedal. This holds true for a cold engine and an engine at operating temperature no matter what the outside temperature is. - Switch on ignition and start engine - At outside temperatures below 0C (32F) press clutch pedal before starting If engine does not start or is difficult to start, go to B. If engine starts normally, advice customer on correct starting procedure.
B. Battery voltage too low Check state of battery charge; charge or replace if necessary Try to start engine again If engine does not start or is difficult to start, go to C.
C. Voltage at coil terminal 15 too low Install additional wire from terminal 1 to ground. Measure voltage at terminal 15 with voltmeter while starter is operating (picture) If voltage is 9 volts or more, go to D. If voltage is less than 9 volts, possible problems are: - Voltage drop in circuit from battery via light switch, ignition-starter switch to coil termianl 15. - Poor ground connection between battery and body and betwen transmission and body. - Starter current draw too high
D. Trouble in cold start device Possible problems: - Cold start valve wire detached from terminal 50 of solenoid. - Wire detached from thermoswitch - Incorrect combination of thermoswitch and control unit. (see list of equipment in workshop manual) - Cold start valve or thermoswitch defective Cold start valve/thermoswitch test instructions: Cold start valve and wiring (WARNING: FIRE HAZARD!): - Detach cold start valve from intake air distributor but leave it connected to the ring main - Pull connector off thermoswitch and connect to ground (picture) - Pull wire off terminal 1 on coil - Operate starter briefly and check if cold start valve injects fuel (catch fuel with rag) Thermoswitch can only be tested at very low ambient temperatures or when switch has been cooled down to actuating temperature in a refridgerator If no trouble found, go to E.
E. Trouble in electrical part of injection system Connect VW 1218 tester and run through test program Possible trouble: - Control unit defective - Temperature sensors I and II defective - Pressure sensor defective - Trigger contacts defective
- Hot engine does not start
Test conditions - Correct starting procedure being used Starting engine: - Gear shift lever in neutral - Do not press accelerator pedal. This holds true for a cold engine and an engine at operating temperature no matter what the outside temperature is. - Switch on ignition and start engine - At outside temperatures below 0C (32F) press clutch pedal before starting - Fuel in tank
A. Valve clearance incorrect Adjust valves properly with engine cold. Warm engine up and carry out starting tests. If engine is difficult to start, go to B.
B. Pressure in ring main too high (mixture too rich) Check pressure with gauge while operating starter. Specified pressure: 2.0kg/cm2 (28psi) Set to correct pressure if necessary Try to start engine again If engine is difficult to start, go to C..
C. Control unit or pressure making mixture too rich Connect tester 1218 and run through test program Correct trouble and try to start engine If engine is difficult to start, go to D.
D. Resistances of temperature sensors I+II too high despite OK indication (mixture too rich) Remove temperature sensors Let them cool down to room temperature and measure resistance with ohmmeter: (picture) - Sensor I, not more than 300 ohm - Sensor II, not more than 2.5k ohm Replace defective sensors and try to start engine again If engine is difficult to start, go to E..
E. Engine floods due to defective cold start device Possible trouble: - Cold start valve leaking - Thermoswitch does not switch off at higher temperatures. (See Thermoswitch actuating temperatures) Correct trouble and try to start engine again If engine is difficult to start, go to F..
F. Injectors leaking Remove injectors but leave them connected to the ring main. WARNING: FIRE HAZARD Switch ignition on and off several times without starting engine If more than two drops are ejected by an injector in 1 minute, replace leaking injector.
- Engine starts but stops again after a short time
Engine starts but stops again after a short time
A. Trouble in electrical part of injection system Connect tester VW1218 and run through test program Possible trouble - Control unit defective - Temperature sensor II (cylinder head) defective - Pressure sensor defective If no trouble found, go to B.
B. Temperature sensor II defective despite OK indication Remove sensor and let it cool down to room temperature. Measure resistance with an ohmmeter. Specified value should be 1.5 to 2.5k ohms. (picture) If resistance too high, to go C. If resistance OK, replace temperature sensor II.
C. Auxiliary air regulator defective Check air flow through regulator with engine cold. If there is no flow or flow is restricted, replace auxiliary air regulator
Idling Trouble
- Rough idle during warm-up
Rough idle during warm-up Test conditions: - Valve clearance and ignition timing correct (very important) - Idling speed of warm engine within specified tolerances - Let engine cool down to ambient temperature before starting test
A. Idle enrichment inadequate during the warm-up phase Start engine When auxiliary air regulator has closed (after 3-4 minutes) measure idle variation If the variation is more tham 100rpm: Type 3: go to C. Type 4: go to B. Variations of less than 100rpm are acceptable
B. Idling CO potentiometer setting too lean Turn potentiometer slowly clockwise until idle is normal (Variation less than 100 rpm) If idle is still varying by more than 100 rpm, go to C. If idle is OK, check that CO is not too high when engine is warm (50C-70C/122F-158F) If the CO is considerably above the permissible maximum, look for fault in "CO value too high" section of guide
C. Idle contact in throttle valve switch not in order Possible problems: - Throttle valve switch incorrectly adjusted - Wire 17 between throttle valve switch and control unit defective - Throttle valve switch defective
- Hunting (surging) at idle at all temperatures
Hunting at idle at all temperatures NOTE: This point concerns only vehicles with deceleration fuel cutoff - Type 3: up to Chassis No. 311 2 500 000 - Type 4: up to Chassis No. 411 2 100 000 Test condition: - Engine warm (50C-70C/122F-158F) - Engine running at idle
A. Leakage in intake manifold Pull auxiliary air regulator hose off at intake elbow and close it with the thumb If idle is steady, go to B. If engine continues to hunt: Pull intake elbow off throttle valve support Close off by-pass drilling with thumb and listen for sucking noises (put picture here) Possible causes for leaks: - Hoses between intake manifolds and intake air distributor - Intake manifold gaskets - Rubber mountings for injectors - Vacuum hoses Eliminate all leaks found
B. Auxiliary air regulator not closing Type 3 (automatic) and Type 4: Run engine and check if there is voltage at the connection on auxiliary air regulator If voltage present, replace regulator If no voltage, check wire to terminal 87 on pump relay and repair. Type 3 (manual) Replace mechanical regulator
- Hot engine stalls at idle
Hot engine stalls at idle Test condition: - Engine cold
A. Valve clearance incorrect Check clearance and, if necessary, set exactly (very important) Warm up engine and check if it will idle properly If engine stalls, go to B.
B. Trouble in electrical part of injection system Connect tester 1218 and run through the guide Possible trouble: - Throttle valve switch incorrectly adjusted - Control unit defective - Pressure sensor defective (too lean)
- Rough idle in driving range (Automatic Transmission)
Rough idle in driving range (Automatic Transmission) Test conditions: - No variation in idle with lever at "N" - Idle speed with engine warm 850-900rpm
A. Idling speed regulator incorrectly adjusted...
stachmen.k