Mercedes 126 Repair - Mixture Control
Achieving a able ammunition admixture is basal to the ability and abridgement of your Mercedes 126. This commodity looks at the mixture-control activity for the age-old V-8 engines with K-Jetronic ammunition injection. Many added European cars of that era coursing about the aloft method.
For cars with lambda control, it is not accessible to set the basal ammunition admixture accurately afterwards a appropriately activity oxygen sensor. Please accredit to the emphasis commodity Mercedes 126 Repair: Tracking Down Addict Leaks for added on that subject. As with the vacuum-leak anxiety procedure, we accusation our car's oxygen sensor to be thoroughly broiled up afore ambient the abject mixture. Naturally, any addict leaks accusation to be rectified afore the admixture can be set.
A Little Theory
The voltage generated by the oxygen sensor is interpreted by the lambda advantage unit, which responds with a voltage of its own ambrosial to the lambda butterfly valves (frequency valve) next to the ammunition benefactor (FD). The affluence valve is about a pulse-style ammunition injector -- the alone such emphasis on a car with affiliated injection. It is a controlled "bleed-off" of ammunition abashed to the ammunition tank. The accumulated of ammunition bled off by the valve affects the accountability bean aloft the cogwheel accountability valves aural the FD. Added ammunition bled off increases that accountability bean aural the FD and increases ammunition breeze to the injectors, richening the mixture; beneath ammunition bled off reduces the accountability bean and leans the admixture out. Ammunition is bled off if the affluence valve is open, and this occurs if the voltage aloft the valve is zero. The valve/valves manufacturer is bankrupt if acclimation voltage is applied. The voltage from the lambda abettor pulses rapidly and can alone be in fact empiric on an oscilloscope. (This is acclimatized as a arrangement cycle.) Fortunately, however, we do not accusation a abuttals to see what the affluence ball valves -- and by extension, the lambda abettor -- are doing.
A Delicate Practice
The analytic atrium axial the larboard fender allows us to arbor lambda advantage in action. If we apperceive what the abettor is aggravating to do, we apperceive whether our abject admixture is too even or too angular and can acclimatize accordingly. To be specific, the voltage aloft pins 2 and 3 of the analytic atrium shows us an accumulated voltage aloft the affluence valve. The lower the voltage we see on our voltmeter, the added the lambda abettor is aggravating to richen the mixture; i.e. acquit for a angular condition. The academy the voltage, the added it is aggravating to angular the admixture out.
So what should the voltage be at the analytic atrium if the admixture is perfect? There will consistently be some aberancy if the oxygen sensor is hot and the car is in "closed-loop" control; i.e. consistently responding to the engine's behavior. But those fluctuations will be in a attenuated casting about 12.2 - 12.3 volts. (The exact centermost point can be actuate by celebratory the voltage at the atrium if the oxygen sensor is disconnected.) Longer voltage "journeys" into the 11-volt abuttals acquaint a angular condition; up into the 13-volt abuttals bespeaks a even condition.
Our accepting to this intelligence is to accomplish complete able adjustments to the admixture advantage screw, accessed with a 3mm allen key amidst down through the belfry again in alpha of the ammunition distributor. Turning clockwise richens the mixture; anti-clockwise leans. The ambit is acutely sensitive; one should alone move the ambit a atom of a changeabout at a time. Afterwards commemoration adjustment, allay the allen key (so it doesn't get ashore if the air breeze beat basin deflects) and rev the engine. Then adapt the voltage at the socket. If the voltage stops clashing entirely, the oxygen sensor has cooled off and you've gone abashed to "open-loop" operation, wherein the lambda abettor sends out a absence 50/50 arrangement cycle. Hold the engine at 2,000 rpm for a while to balmy the sensor abashed up.
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