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Sandro liked 2 days ago
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Marcus Johnson
Diagnose never Guess
------Full p0300 diagnose---- 2019 Ram 5.7 hemi port fuel rail injection----Customer states had oil changed at another dealership up north in Wisconsin and shortly after vehicle ran rough and ses light was on. Checked for correct oil level and oil grade both were fine . Checked for dtc's Found p0300 multiple cylinder misfire and p0305 cylinder misfire in as active in pcm while engine ran at idle. looked at mis fire monitor and saw cylinder 5 and 8 were misfiring the most up into the 40s on misfire counts. Swapped coils misfire did not move. So now I was like hmm now you got my attention hemi. Performed quick compression check on corresponding cylinders looked at spark plugs no problems found there. Decided to ohm test cylinder 5 and 8 injector both were at 10.53ohms and 10.64 ohms they seen in pictures 1 and 2 so there were not open. Is it the pcm ....nope used n2 to check injector signature pulse in pictures 1,2,3 then verified with picoscope that showed pcm was fine but still misfire present. Next I finally used a OEM scan tool to turn on and off each injector individual lol with engine off and discovered cylinder 5 and 8 did not click but remember there not open right? But they could be clogged and the inner pintle can't open or shut. Sure enough performed current ramp of these two injectors and saw a very low ramp waveform. So installed two new fuel injectors then checked... (More)
Sandro liked 2 days ago
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Cop experiment I did last year, yes the n2 can see the coil fire but there was not much detail outside of that. Used a relay because of the copper winding with the diode removed so no signal clipping was taking place second waveform is from a higher sample diy scope. It's just a another example of how the n2 graphing feature can be used in some cases as a first check diag tool.
Marcus commented 5 days ago
How do I set up to current ramp a fuel pump with the amp clamp?
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