Crank/ No Start Analysis - 2010 Mini
Just sharing a recent analysis/repair that we just finished today. Vehicle is a 2010 Mini Cooper S that came to us as a crank/no start, the owner had already done everything he knew to do essentially just spark plugs. He said they tried spraying cleaner in it to start it also...then gave up. To us...we pushed it into the shop and Nate started checking it out, it smelled like it was flooded, but would fire every once in awhile, he then tried clear flood cranking it, still wouldn't start.
I was out there just being nosey and at that point suggested going with an in cylinder transducer, he ran all four cylinders and saved the files for later analysis.
Although there isn't usually much valve timing information available cranking, I was going to try anyway, Nate is still learning (me too, as far as that goes), and now everyone can take what they want from the waveforms.
Looking at the waveform, I believed we had a valve timing issue, I sent pics of the waveform to a friend to look at, he replied... no usable information, especially on that engine...he suggested we pull the valve cover to look physically instead of using the waveform. We were already in process of pulling it anyway since it is easy and the components are visible from that point. The top chain guide was mostly gone and a couple of the others had chunks missing. From there the job was sold and completed...the remaining waveforms are post repair:
Ok im not good at the analsis still have more questions than answers. How ever i know what a good cranking waveform looks like and that is not good and would justify selling tear down. They say there is no real information in a cranking wave form. I disagree. Wish you would have of taken pictures to go along with the waveform.
Still learning as well . But that cranking waveform definitely doesn’t look like the ones I seen . Atleast now we have a known good :) thanks for the post rusty
This cranking waveform shows just what is occurring within the cylinder, please look at Figure 2 (Crank no start zoomed). The first part of the waveform to examine is the exhaust valve pocket. This pressure change shows when the exhaust valve opened. Under a cranking condition the target for the pressure change is 30-60 degrees Before Top Dead Center (BTDC). This pressure change produced from the exhaust valve opening is late at approximately 10 degrees BTDC. This indicates that the exhaust camshaft is two teeth off (the rule of thumb is 15 degrees for each tooth). Now examine the intake pressure change after the 360 degree point (TDC). There is a pressure drop that occurs at 30 degrees After Top Dead Center (ATDC) (Note; this should occur at the 360 degree point). This drop in pressure is produced from the downward movement of the piston. As the piston moves away from the head a negative pressure (vacuum) is created within the cylinder. If the intake valve opens late the pressure within the cylinder is already in a negative pressure state, thus the pressure drops as soon as the intake valve opens. This shows that the valve opening is 30 degrees late. Now look at the intake valve closing that occurs after the BTC position. The pressure change is occurring at the 90 degree ABDC position. This shows the intake valve opening is late by 30 degree. (Note: the correct position for this pressure rise is 30-60 degrees ABDC). This cranking in cylinder pressure waveform clearly shows the camshaft timing is approximately two teeth late (retarded). If one learns how to interpret the pressure changes that occur within the cylinder there is indeed a lot of valuable diagnostic information contained.