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Mercedes Sprinter long crank time when hot

Posted By ianboyle Monday, June 15, 2015 9:40:11 AM
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ianboyle
 Posted Monday, June 15, 2015 9:40:11 AM
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Hi,

If anyone had the cam crank waveform for this 2005 416 CDI Sprinter 2.7L engine I would be interested in comparing it to my own. This van has a very long crank time when hot but not everytime, about 1 in 4 times when hot it will turn over for between 3 - 10 seconds before starting.

I took numerous waveforms of fuel rail pressure, injector current, starter current. I noticed the injector initially fires a bit early in the compression stroke. So then checked cam and crank correlation. Attached below is an image of the cam crank. I will also put on the fuel pressure (high and low fuel pressure sensors) with the starter current and injection picoscope files see if anyone has any insight on the next post. Should the missing tooth line up with the middle of the cam signal or should it be offset as it is shown below, thanks.



http://www.bba-reman.com/forums/Uploads/Images/d8121ee8-801f-4b63-96c8-d7fe.jpg
ianboyle
 Posted Monday, June 15, 2015 10:07:06 AM
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I was going to upload the psdata files but looks like I've exceeded my available space. Is that a daily limit or an overall limit. I'll try again later. But for the minute if anyone knows if that cam and crank are correct I'd be grateful,

Ian
SB126
 Posted Monday, June 15, 2015 11:00:31 AM
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Delete some of your other files,

Or compress the PSD files and post them as a ZIP
ianboyle
 Posted Monday, June 15, 2015 4:15:41 PM
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I'll throw them up as a zip file, thanks
ianboyle
 Posted Monday, June 15, 2015 4:40:39 PM
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This psdata file shows the Cam and Crank correlation as well as the injector firing before the peak of the compression stroke. Its the injection timing that's catching me out as I would have thought that the injector should be fired at TDC of the compression stroke
laldog
 Posted Monday, June 15, 2015 6:04:27 PM
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Sorry i cant see the files on here but whats the cam/crank look like when running OK? Also any codes and is fuel pressure fine on cranking?
ianboyle
 Posted Tuesday, June 16, 2015 4:15:08 AM
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Sorry i cant see the files on here but whats the cam/crank look like when running OK? Also any codes and is fuel pressure fine on cranking?

Hey here is the image from above, to me the reference missing tooth on the crankshaft (red) looks offset to the camshaft (blue) reference. There are 7 teeth on one side of the reference and 19 on the other where the cam signal drops to 0V. Sorry it didn't upload with as good a quality as I would have liked but the injection firing (in yellow) can be seen still a bit early on the compression stroke (in green).




http://www.bba-reman.com/forums/Uploads/Images/d8121ee8-801f-4b63-96c8-d7fe.jpg


There are no fault codes at all. The fuel rail pressure waveforms I have taken show the pressure sensor reaches 1.1 volts from its plausibility value of 0.5 volts which I would have thought is good enough but sometimes the injectors aren't commanded to fire until sometime after (3 - 5 seconds) even as it starts creeping back to 1 volt.
Tuesday, June 16, 2015 4:17:41 AM by ianboyle
Robski
 Posted Tuesday, June 16, 2015 7:09:52 AM
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The fuel rail pressure waveforms I have taken show the pressure sensor reaches 1.1 volts from its plausibility value of 0.5 volts which I would have thought is good enough
you want 1.3V don't you (Bosch) ?

Got a sensor sim ?


Rob.
ianboyle
 Posted Tuesday, June 16, 2015 8:38:02 AM
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Ok that could be my issue then. I seen injector current occur at 1 volt and assumed that was the trigger, but looking back at them now, injection was much more common at 1.3v. Also there seems to be a bit of dropout on the pressure sensor signal which I thought was a faulty connection but may be actually the pressure building being affected by the low pressure pump. I'll take a scope of the low and high pressure pump with injection and put them up
Tuesday, June 16, 2015 8:44:34 AM by ianboyle
ianboyle
 Posted Tuesday, June 16, 2015 9:10:21 AM
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I added two png files of the fuel rail pressure from the high and low sensors with starter cranking current and the cylinder 1 injector current. On the 2nd image the pressure reaches 1.3v but injection doesn't fire for a few seconds. Thanks for any input.

Also there is a lot of signal dropout on the 2 sensors but I starting to think this could be a bad earth connection on the scope wire as both channels mirror each other, but this could be also the pressure fluctuating and causing my problem.

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