Well now, This looks suspect!! Flywheel sensor - Page 2 - PeachParts Mercedes-Benz Forum

Cap'n Carageous · #16 05-30-2002, 09:55 AM

Where is the "hall effect" sensor? I thought that it was on the back of the speedometer. Anyway, there appears to be two wires inside this cable. It looks like a green wire wrapped in woven wire, like co-ax, but they are definitely touching and will need replacement. I was just wondering if a shortage here will make the engine skip.

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.

jay123 · #18 06-08-2002, 10:45 AM

The crankshaft sensor sends a signal to the EZL/Ignition Module. The EZL then sends a signal to the coil to spark to the cap tower then to the rotor. If the sensor is defective, you will never get a spark. If the wires are frayed, you may get an intermittent spark which would cause misfiring, rough idling, and errors when the system is checked.
Hope this helps and keep us informed as to what happens.

Cap'n Carageous · #19 06-08-2002, 04:08 PM

I installed a new one. Engine is still on the stand so I don't know anything yet. I plan to get a reman transmission early next week and have it back in by next weekend. Yall pray for me!!

JimF · #20 06-09-2002, 02:15 PM

Have some info on the L5 sensor (as it's called in my car). Check my page (www house) and click menu #5.

If bad, the CE light is turned on immediately. With an ohmeter, a good one ohms out to 850 ohm +/- 5%. Also it should be shielded since the signal needs to stay "clean" getting to the DI module. If broken as your is, it needs to be replaced or fixed so that the shield is 'integral' to unit. Best to replace it.

JohnEspeed · #21 09-10-2002, 09:55 AM

Can this sensor be affected by heat?
My engine on my '87 190E 2.3 suddenly cuts out(no warning) after it gets hot. It passes 100 ,fan comes on and cools back to about 80, then it dies. Apperently I then get no spark, and car doesn't start until it cools (10-20 min).It then runs fine until it gets hot again. Idle seems ok.Car starts better when cold out. Cranks a few seconds before starting when warm out.
I have changed the coil, and installed newer OVP, but problem persists.
Please help!

Cap'n Carageous · #22 09-10-2002, 10:19 AM

I wouldn't think that heat will cause the sensor to exhibit the problems you are seeing. As a matter of fact, I replaced the sensor on mine and nothing changed. Another $95 down the drain.

JimF · #23 09-10-2002, 10:57 AM

and the DTC was "Chrankshaft (L5) sensor". The CE light would come on but the car drove and ran ok.

This is the only problem I've had with my car and, in fact, it was this problem that led me to learn about the electronic control systems in the car. And this led to my Mercedes web page.

It turned out to be the DI module, (Menu #5). The module was FUNCTIONALLY ok but had a bad memory bit in the stored faults memory that said the L5 sensor is bad. Similar to a computer with a bad memory chip.

The DI module was functionally ok (except for the bad memory 'bit'. This then caused the DM module to activate the CE.

All of this info as you can see is probably similar to your problem. If possible, swap your DI module out and I'll bet that will fix the CE!

My fix was to buy a used DI module from a NYC parts yard for $200! A new one lists for $1100.

Cap'n Carageous · #24 09-10-2002, 12:55 PM

I have spent some time there before on several occasions. Question is, is my EZL as complex as yours on the 94? I don't have fault storage in my CIS-E controller so would I have memory in the DI. If that is the case and replacement of the DI was the solution then you would be my hero. I'd buy you a steak even if I had to mail it to you!!

stevebfl · #25 09-10-2002, 05:16 PM

There are two types of timing triggers used in various ignition systems. MB uses inductive sensors. These are coils that induce AC voltage as iron is passed near by. These are two wire sensors and actually generate electricity. Hall type sensors have three wires and produce a DC pulse rather than AC. They are powered and generate no electricity of there own.

Miss a signal for a moment and you will miss ignition for that same moment

The only codes are real time duty-cycle codes, no impulse codes.

JimF · #26 09-10-2002, 08:11 PM

I thought your car was a '94. Sorry! My comments are not applicable to your car as Steve pointed out.

Cap'n Carageous · #27 09-10-2002, 08:36 PM

Aw shucks, I thought I saw light in the tunnel!! Oh well, maybe some day..............

mplafleur · #28 09-11-2002, 07:26 AM

We call them VRS sensors (variable reluctance sensor). They are commonly used now instead of Hall Effect sensors for crank/cam/wheel speed and position timing. For instance, you can have a maetalic toothed wheel passing the sensor creating a sine wave whose frequency corresponds to the speed of the wheel. If you know how many teeth are on the wheel, you can determine how fast the wheel is turning. If you remove a tooth on the wheel, (called a missing tooth wheel) you will get a gap and a higher signal where the gap occurs. This lets you know when, for instance, you passed TDC. Now you can accurately time you spark and fuel.

190dee · #29 05-25-2003, 04:35 PM

Cap'n: did you tachometer in the instrument cluster drop as the engine "stumble"? I also have the ezl ignition unit.

I have a similar problem. I did measure resistance in the sensor that is located in the front of the engine(M102). Resistance witin specs. I did also try to wiggle the coax cable because the "stumbling" is very random. No difference.

All the resitance specs were within limits described in the service manual. I did do all the test but since I don't have a scope to "see" the signal sensor generates. Could a very dirty sensor generate less voltage output in signal?

Where is the sensor on flywheel located? Engine; M102 -87 not 16 valve

Stevebfl: Could you verify if this ignition module(ezl -87) has an internal pulse or an external trigging sensor? I read another post where you had written something about this.

Any ideas?! Sorry for bumping a old thread.

Cap'n Carageous · #30 05-26-2003, 08:16 AM

My tach did 'stumble' but anytime you lose rpm it will, so that probably is not a factor here. More of an effect than a cause. As far as the location, on the 103 it is behind the oil filter in the top of the bell housing. It will have to be directly in line with the flywheel, regardless of which side it's on.