Dear Forum:

My E320 1995 will not start! It is down now for over a week. The idle was not perfect and it rattled a little but if put in neutral it was very smooth. However, the car was hard to start one morning. Needed to be cranked over a couple of times and subsequently did not start the next morning!

No spark..

I replaced the cam shaft position sensor, ECU and OVP relay. There was definitely a problem with the OVP and the ECU only got power on one of the pins. Now since I replaced the OVP the ECU (and a second ECU) give me a consistent error of 24 and will not generate a spark. 2 month old coils and spark plug wires as well as spark plugs and O2 sensor.....

I now find my spark plugs to be wet so I know I get fuel..

What is my problem? I know error code 24 is the CKP sensor or magnet for position sensor not recognized.

I used an oscilloscope to measure the crank shaft position sensor output see attached trace. I get 5 spikes with approximately 5 Volts followed by a 6th spike with a voltage of about 13Volts. (see attachment) I assume the larger spike defines the position of the cylinder #1?

Car still has no spark..

Is this the correct output of the CKP? Remember I did not measure it loaded by the computer circuit. (High input impedance of the scope!) Should I measure it with the computer connected?

I also measured the voltage on the ECU pin from the adjuster magnet and get 12.7V! DO I assume correctly that the ECU is checking if this voltage is present?

What is going on why don't I get a spark. This mystery has to be solved one way or the other!

Here the mystery continue... !

If I reset the ECU I get a spark for two tries and then it is blocked and the error code 24 appears again...

I now put a scope directly on the CKP (yellow trace) and Cam sensor (magenta trace) pins at the ECU and measured the attached trace. It seems the senor output are correct but I am not sure about the timing!

I also checked the cam adjuster magnet. It has 5 Ohms resistance and if I ground it it will energize and I hear a click! It draws about 2 A.

Here is the catch! IF I energize the adjuster magnet the timing between the CKP and CAM sensor do not change! Is my adjuster magnet stuck in the position used at high RPMs? Do I have to open the top of the engine? Did anybody come across this?

Attached Files

Timming E320 CKP and CAM sensors.pdf (94.9 KB, 282 views)

CKP is located on top of the bellhousing behind the oil filter.

There is also a magnetic pickup at the very front of the engine is this my problem?

In my experience the pick-up in the bell housing has always been the culprit.

my 93 m104 2.8 , also had the issues with no spark, after replacing the pick-up in the bell housing, everthing was back to normal.

I replace the sensor and measured the output with a scope. See above.. Still puzzled!

Help is highly appreciated..

Did anybody come across this one?

Could this be a problem related to the adjuster magnet being stuck?

hello,

the only help i can offer, is for you to post the testing procedure which you used, and then i can try the same on my car. then i can report back my findings. i have a digital multimeter, but am not very familiar with all of the electronic components on the M104, so try to be specific.

hope you get her running soon,
tim