PeachParts Mercedes-Benz Forum - View Single Post - Well now, This looks suspect!! Flywheel sensor

mplafleur · #17 05-30-2002, 11:52 AM

Tha hall effect sensor is one you show pictured. The engine has two of those. One one the harmonic balancer and one on the toothed flywheel.

The one on the harmonic balancer will give a pulse when the steel dowel that is sticking out of the plate passes by. The engine strategy will use it to determine TDC. It then can sequentially fire the injectors.

If it is indeed shorted it can cause a hickup. Upon startup, the controller needs to first see the signal to start the sequential fire, or will probably just bank fire the injectors. This is normally done during crank anyway.

The other sensor on the flywheel would be used to determine engine timing. It is no good unless TDC can be determined. I don't know how many teeth are on the wheel, but it is probably evenly divisable by the number of cylinders. Each pulse is a known number of degrees in a revolution. Each pulse looks like the other and you don't know where you are if you didn't get a pulse for TDC.

If the balancer and the flywheel are both on the crank, I don't know how the controller knows if you are on the compression stroke or the exhaust stroke. There is usually a sensor on the cam for this. Some engines fire on both the compression and the ezhaust stroke but what about injection? Can anyone answer this?

It seems that the wires are in a shielded coax. This is helpful in keeping out radiated emissions. Since the wire is in the engine bay, it is suseptable to picking up noise from the coil fires. We don't need more signal spikes on the wire to confuse the controller.