We have a John Deere 310 SG engine serial number is RE4045T452886. We have a misfire on cylinder one I believe under a no load situation and when the engine is warm. I verified cylinder one with an infrared thermometer, and it was about 80° colder than companion cylinders. We replaced the number one injector with a factory pencil injector with no change. We sent the ECM amount to be tested and to come back OK. I don’t trust this a whole lot, but there is nothing obviously wrong. I cracked the injector lines and noticed a little different spray pattern out of the number one injector. I’m leaning towards an injection pump, but I’ve read on other sites that the ECM‘s can be a problem. My question is does a current ramp graph test show a bad pump or is there any other way to test I don’t have direct access to any John Deere diagnostic tools. I do have 25+ years in the automotive industry, but for diagnostics, but obviously this is a completely different diagnostic platform. Any help would be appreciated before I plunge into a large purchase of either a injection pump or an ECM.
Welcome to HEF plumblevelsquare2020 ! It is tough to determine the issue without Service Advisor. Below is a screen shot from a scope. Check your messages for the interpretation.
Thanks for the info. I tried my 15 year old low amps probe that goes to my lab scope today but it had gave up the ghost. I’m trying to find a friend in the industry that I can borrow. I seen that wave form in the manual but your explanation will help in determining the values I need. I will report back.
Here is my amp profile at idle with no apparent misfire.
Sorry, that does not help. The pattern I show above was for reference only. I did not break down the valve closing times, decay times or the shutoff adjustments on that pattern. The explanation in the first attachment is explaining what you see in the second attachment. So, what I am saying, to troubleshoot it accurately, you need Service Advisor. The diagnostics also has to occur during the misfire event.