I've always found that fuel pumps are a binary thing. They operate, or the do not. Never experienced partial operation condition.

I'm not saying it's not possible, just never seen it myself.

You may have developed some condensation water in the fuel, in which case it will clear itself up, or you can hasten with drygas. Found out with the 300E that water in the fuel will be evident after you park nose down but not nose up. Presents as a baffling intermittent problem (like yours).

Got my water from contaminated gas station tanks.

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1986 300E 5-Speed 240k mi.