Mercedes-Benz W126 fuel pressure regulator and pressures
W126 fuel consumption suddenly rose, could the fuel pressure regulator be the cause?
Yes. If the regulator's spring or plate has oxidized, it does not change the pressure as the engine warms up and the injection runs at full pressure all the time. Consumption can rise sharply. A faulty regulator can also make the car run poorly or stall.
What is the correct fuel pressure on the W126 KE-Jetronic injection?
With a warm engine, the lower chamber pressure must be 0.4 bar lower than the upper chamber. On the M103 engine the upper chamber pressure is 5.3-5.5 bar, so the lower chamber has 4.9-5.1 bar. The measurement is taken from the plugged port of the distributor. Other reference values vary, so check the correct value for the engine.
W126 fuel pressure disappears overnight, does the fuel distributor have to be taken apart?
Not first. Pressure only disappears if fuel can leak out somewhere. First check the check valve, the accumulator, all the injectors and the start injector. Taking the distributor apart is the last option, once the fault has been established in the distributor.