Thanks for the excellent advice. It turned out to be 2 of the fuel delivery valves! Each of my 300 D’s is running purrfect thanks to your tools, manuals and advice. I’ve attached a photo of my 300 D’s. Feel free to use it and my name as reference on your website. I’ve told countless people here in Colorado about your site. Thanks again for helping me get these diesels up and running. Each runs and drives like new. Oh, and thank Kent for me as well.