Mercedes s430 coil and injector timing

Mike Mobile Technician Illinois Posted   Latest  
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Driveability
2003 Mercedes-Benz S430 4Matic 4.3L (113.948) 5-spd (722.6)
Intermittantly Dme Fails To Correctly Id Cylinder 1
Crank / No Start

Intermittently this Mercedes will crank no start. When this occurs, cylinder 1 ignition and injector will fire when cylinder 6 should be and so on in the firing order. Every event is happening 360 degrees out of time. The camshaft and crankshaft correlation is identical between the correct firing and 360 out firing. It is unpredictable when this event will occur. No trouble codes. Has aftermarket cam and crank sensors. Thinking dme fault hoping I’m not missing something. First file is fuel Disabled cranking when event was not occurring. Second is when it’s a crank no start. ignition primary waveform is cylinder 1. Sorry about the pics!

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Eric Technical Support Specialist
New York
Eric Default
 

Question: has the transmission and or flex plate been out of this vehicle prior to this symptom?

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Solaman Owner/Technician
Trinidad and Tobago
Solaman Default
 

Hi,last time I have an issue like this it was 3 bent tooth on the flex plate,last repairer removed the transmission to sort out some leaks and while the tech was tightening the torque converter bolts he pry on the flex plate to turn​.​The car was towed in​.​Crank angle sensor wave pattern is consistent though.

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Mike Mobile Technician
Illinois
Mike Default
   

I do not know any history on this Mercedes before today. I did visually inspect the flex plate turning by hand and running it had slight runout but didn’t see any bent teeth or cracks, The engine will never stall once running, its is only when trying to start. Engine starts 90 percent of time and will run indefinitely. 10 percent it will fire 360 out.

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Dmitriy Analyst
Ontario
Dmitriy Default
   

Mike, the car uses CMP signal to identify the cylinder from revolution 1. If something is not right with the CMP signal at first, but later the signal becomes normal (happens sometimes with aftermarket sensors), you would not notice that in captures for later times. It would be helpful to redo the captures at 1s/div timebase, 5MS across the screen and attach psdata files. Another thing to…

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Mike Mobile Technician
Illinois
Mike Default
   

Dmitriy, yes I am backpinned at the dme. I have compared both files at the first 3 or 4 cam crank synchs after cranking. They are exactly the same. I will post the pico file tomorrow. Thanks!

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Richard Technician
New York
Richard Default
 

I am having a bit of trouble seeing it clearly, but it appears the amplitude of the Cam signal is different between those files. Can you provide us with the files so we could see them better?

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Eric Technical Support Specialist
New York
Eric Default
 

Great eye Richard. I noticed that too after zooming in. The good timing screen shot the CMP signal amplitude looks to be 5V to down to about 300mV. The screen shot with the symptom looks like about 7V to 0V....... Again, nice observation. I had to zoom and squint myself to see it (old guy syndrome?).

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Eric Instructor
California
Eric Default
   

delete

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Stephen Technician
Tennessee
Stephen Default
 

I wonder if the answer is in the part of the theory of operation, that you posted but is cut off where it tells how firing position is determined when the CMP pulse is missing. So it should start, long crank, even without the CMP.

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Mike Mobile Technician
Illinois
Mike Default
   

Ive spent the last hour trying to upload this file and it refuses to work. I think I found the problem. It appears to be in the cam sensor signal I think. When the 360 out firing happens the cam sensor is staying low for too long and the are two ckp missing tooth on the first 720 degrees of rotation in the low spot of cam sensor then after that initial rotation it starts working correctly. Again…

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Dmitriy Analyst
Ontario
Dmitriy Default
 

Mike, glad you now have evidence needed to advance with the diag. One person that should receive a round of applause is Bob Powell. Learned a lot from his aftermarket cam sensors saga: diag​.​net/msg/m3kynk2dzk…

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