If you can see the spring that pushes lever that tensions the oil pump chain, look for wear where the spring touches the lever. Mine was almost worn through also, check the screen on the oil pump pickup for any stringy debris that might me ready to sneak through the screen. That screen is hardy, but pretty coarse.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.