The oil pressure sending switch is a common problem on Rangers. Of course, you don't really know if that's what's causing the gauge to drop or if it's real. I'd get it swapped out pronto. It is not too expensive and simply screws into the block with a dab of sealant on the threads.
On your 3.0L, the sending switch is in the block behind the PS cylinder head - hard to see from above. Go in through the wheel well and push the rubber splash shield out of the way for a better view. The wire to it is dark green/white.
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On your 3.0L, the sending switch is in the block behind the PS cylinder head - hard to see from above. Go in through the wheel well and push the rubber splash shield out of the way for a better view. The wire to it is dark green/white.
