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K-Jetronic is a mechanical system: the fuel is continuously metered in proportion to the quantity of air drawn in by the engine. The K-Jetronic system was installed as Original Equipment in series production vehicles in the years 1973 through 1995. Since then, the K-Jetronic system has been only of significance for repairs and maintenance.
SYMPTOM: ENGINE DOES NOT START/STARTS HARD WHEN COLD
Cause |
Remedy |
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| Auxiliary air valve does not open |
Check valve for correct function |
| Electric fuel pump not operating |
Check pump fuse, pump relay and pump |
| Cold start system defective |
Check cold start system |
| Therm-time switch defective |
Test thermo-time switch |
| "Cold" control pressure outside tolerance |
Test pressure |
| Injector leaking, opening pressure low |
Check injectors on tester |
| Injected fuel quantities unequal |
Check for equal fuel quantities |
| Basic idle setting incorrect |
Check and adjust CO level |
SYMPTOM ENGINE DOES NOT START/STARTS HARD WHEN WARM
Cause |
Remedy |
| Leaks in air intake system (false air) |
Check air system for leaks |
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| Air flow sensor plate stop incorrectly set |
Check and reset |
| Electric fuel pump not operating |
Check pump fuse, pump relay and pump |
| "Warm" control pressure too high |
Test pressure |
| Fuel system leakage |
Inspect fuel system for leaks |
| Injector leaking, opening pressure low |
Check injectors on tester |
| Injected fuel quantities unequal |
Check for equal fuel quantities |
| Basic idle setting incorrect |
Check and adjust CO level |
SYMPTOM: IRREGULAR IDLE DURING WARM-UP
Cause |
Remedy |
| Leaks in air intake system (false air) |
Check air system for leaks |
| Auxiliary air valve does not open |
Check valve for correct function |
| Cold start valve leaking |
Check cold start valve |
| "Cold" control pressure outside tolerance |
Test pressure |
| Injector leaking, opening pressure low |
Check injectors on tester |
| Injected fuel quantities unequal |
Check for equal fuel quantities |
| Basic idle setting incorrect |
Check and adjust CO level |
| Lambda control system not functioning correctly |
Check Lambda control system |
SYMPTOM: IRREGULAR IDLE WITH WARM ENGINE
| Cause |
Remedy |
| Leaks in air intake system (false air) |
Check air system for leaks |
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| Cold start valve leaking |
Check cold start valve |
| "Warm" control pressure too high |
Test pressure |
| "Warm" control pressure too low |
Test pressure |
| Injector leaking, opening pressure low |
Check injectors on tester |
| Injected fuel quantities unequal |
Check for equal fuel quantities |
| Basic idle setting incorrect |
Check and adjust CO level |
| Lambda control system not functioning correctly |
Check Lambda control system |
SYMPTOM: ENGINE WILL NOT ACCELERATE, BACKFIRES
| Leaks in air intake system (false air) |
Check air system for leaks |
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| "Warm" control pressure too high |
Test pressure |
| "Warm" control pressure too low |
Test pressure |
| Basic idle setting incorrect |
Check and adjust CO level |
| Lambda control system not functioning correctly |
Check Lambda control system |
SYMPTOM: ENGINE BACKFIRES UNDER LOAD
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| Electric fuel pump not operating |
Check pump fuse, pump relay and pump |
| "Warm" control pressure too high |
Test pressure |
| Primary system pressure out of tolerance |
Test pressure and adjust with shim |
| Injector leaking, opening pressure low |
Check injectors on tester |
SYMPTOM: POOR PERFORMANCE
| Leaks in air intake system (false air) |
Check air system for leaks |
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| "Warm" control pressure too high |
Test pressure |
| "Warm" control pressure too low |
Test pressure |
| Primary system pressure out of tolerance |
Test pressure and adjust with shim |
| Injected fuel quantities unequal |
Check for equal fuel quantities |
| Throttle butterfly does not open completely |
Check butterfly and stops in throttle venturi |
| Lambda control system not functioning correctly |
Check Lambda control system |
SYMPTOM: ENGINE RUNS ON
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| Air flow sensor plate stop incorrectly set |
Check and reset |
| Cold start valve leaking |
Check cold start valve |
| Injector leaking, opening pressure low |
Check injectors on tester |
| Basic idle setting incorrect |
Check and adjust CO level |
SYMPTOM: FUEL CONSUMPTION TOO HIGH
| Cold start valve leaking |
Check cold start valve |
| "Warm" control pressure too low |
Test pressure |
| Basic idle setting incorrect |
Check and adjust CO level |
| Lambda control system not functioning correctly |
Check Lambda control system |
SYMPTOM: DRIVING PERFORMANCE UNSATISFACTORY
| Leaks in air intake system (false air) |
Check air system for leaks |
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| Excessive fuel delivery to control circuit |
Check fuel delivery |
| "Warm" control pressure too high |
Test pressure |
| "Warm" control pressure too low |
Test pressure |
| Primary system pressure out of tolerance |
Test pressure and adjust with shim |
| Basic idle setting incorrect |
Check and adjust CO level |
| Lambda control system not functioning correctly |
Check Lambda control system |
SYMPTOM: CO CONCENTRATION AT IDLE TOO HIGh
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| Cold start valve leaking |
Check cold start valve |
| "Warm" control pressure too high |
Test pressure |
| Basic idle setting incorrect |
Check and adjust CO level |
| Lambda control system not functioning correctly |
Check Lambda control system |
SYMPTOM: CO CONCENTRATION AT IDLE TOO LOW
| Cause |
Remedy |
| Leaks in air intake system (false air) |
Check air system for leaks |
| Sensor plate and/or plunger not moving freely |
Check for free movement |
| Basic idle setting incorrect |
Check and adjust CO level |
| Lambda control system not functioning correctly |
Check Lambda control system |
SYMPTOM: IDLE SPEED CANNOT BE ADJUSTED (TOO HIGH)
| Cause |
Remedy |
| Auxiliary air valve does not close |
Check valve for correction function |
SYMPTOM: ENGINE STARTS BUT IMMEDIATELY DIES
| Cause |
Remedy |
| Electric fuel pump not operating |
Check pump fuse, pump relay and pump |
| Excessive fuel delivery to control circuit |
Check fuel delivery |
| "Warm" control pressure too high |
Test pressure |
| "Warm" control pressure too low |
Test pressure |
| Primary system pressure out of tolerance |
Test pressure and adjust with shim |
