I just purchased a 2004 E500 wagon with the 5.0L V8 from Copart and am having a hard way to go with the engine. It starts easy and runs nice and smooth but has a very noticeable tapping sound coming from the driver's side cylinder bank. It's not horribly metallic sounding and isn't a sharp/loud sound, however it's very rhythmic. I have a hunch that it's within the fuel system of the car as the very first fuel injector closest to the front of the car seems to (maybe) be the culprit. I've had the belt off of the car and ran it for a few seconds to conclude that none of the accessories are causing the noise. I will be uploading a video very shorty that demonstrates the sound. Does anyone have any preliminary ideas?

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'83 300D Turbo Diesel
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'84 300D Turbo Diesel