My truck is pouring oil from somewhere in between the firewall and the block on the passanger side,I thought it could have been the oil filter loosened up or something but it is much higher and further back where I can't see it of course.It's a 94 3.9 it's only got 123 thousand on it and this thing is really starting to go sour.

 

Its the oil pressure sending unit.

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And you need a large, deep socket (I can't remember the exact size) to remove it, or the special tool in the picture (part number c-4597).

 

Yep, thats the first thing that came to my mind too. Theres a thin plastic diaphram in it that could crack.