Mercedes-Benz 560SEL starting difficulties, exhaust black smoke

         Symptom: a Mercedes-Benz 560SEL type electronic injection V8 engine, because the place is too long, difficult start. After starting idle instability, and the exhaust black smoke, the engine accelerated to 5000 rpm or so, start ups and downs, especially powerful.
         Troubleshooting: Why start to solve the difficulties. First look at the fuel pump to the engine oil pressure pump oil is normal, so again the spark plug removed for inspection, the results have been drowned gasoline spark plug failure is blocked by the differential pressure valve gasoline dispenser on the basis of this phenomenon can be positive or poor result, the differential pressure valve removed, the differential pressure valve is really dirty actions, after cleaning, the engine smooth start, but after obd scanner starting idle instability, exhaust black smoke, this is because the mixture is too thick here it must be noted, after removing the differential pressure valve clean (as long as the differential pressure valve with electromechanical engines) must be adjusted, usually after the differential pressure valve adjustment screws loose 4-5 laps then, after a good adjustment, troubleshooting. But when the engine is accelerated to 5000 rpm when the throttle foot in the end, is not up to speed, and turn around in 5000 fluctuated, very serious, according to experience, this situation is caused by the engine off the oil. First return pipe with pliers, not to death, then accelerated, found that the situation has improved, it is not enough due to the engine oil pressure caused by high speed, but the front has measured the low-oil pressure is normal, indicating that the pump is good. So remove the pump relay, for a new piece, the failure to completely ruled out.
         Failure Analysis: This electromechanical engine is more difficult to repair. Its fuel distributor on the engine fuel injection is mainly played the role of the amount allocated between the two cylinders, but the size of the fuel injection quantity is to rely on the differential pressure valve to adjust the fuel distributor, the adjustment NEC PRO57 screw on the pressure valve, inside tune too much, it will make the mixture too thick black smoke, tune a little, and the mixture is lean, the engine underpowered, so just to be transferred so far. Engine speed and down because the pump relay has two contacts, one pump low speed contact, a high-speed contact, when the engine speed reaches 4000 rpm, the speed on the pump relay contacts should be closed so that the pump high-speed operation, in order to supply engine oil needs, this time, the high-speed contact is not closed, causing the engine oil pressure is not enough, not enough engine speed needs, start the engine speed fluctuated.
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