The 5.4 is a great engine and usually doesn't have any known problems with the oil pump. What I recommend is this. Go to the parts store and ask if the lend or rent mechanical oil pressure gauges. Get one. Remove the oil switch you just replaced and screw in the connecter for the mechanical pump. That way you will know how much pressure you actually have. Also, keep in mind, if you have no oil pressure, the engine will start knocking and ticking. If you don't hear any of that, then it has pressure regardless of internal gauge. I do recommend getting a mechanical gauge just to check it.
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Monday, January 17th, 2011 AT 3:27 AM