flat oil pressure gauge

Bad sender... possibly an open in the circuit, bad cluster..... possibly no oil pressure but I would expect the cam followers to let me know. Sender is locate beside the oil filter on the 4.6.

All the same, I wouldn't drive it without knowing for sure if I have oil pressure or not...

First order of business is to put a mechanical oil pressure gauge on that engine and confirm if you do or do not have oil pressure. If you don't have any oil pressure DO NOT run the engine any more until repaired.

Fords "idiot" oil pressure gauges are poor at best, they are dampened so nobody gets excited about normal pressure fluctuations, and they never show an actual pressure value. You can check the throw of the gauge by unplugging the sending unit, and taking a jumper wire and grounding the lead that plugs onto the oil pressure sending unit. With that lead grounded your gauge should show full/max scale. If it doesn't work properly I suggest you consider installing a real oil pressure gauge.

Good Luck

I can top that. My 2000 4.0 L oil gauge is pointing straight down. When turned off the needle would rest on the needle stop. Well somehow it's flipped around and is under that needle stop now. No Engine running points straight down, when you start up it jumps up to peg at the needle stop, good enough for me. There is good pressure but we've had problems with this idiot oil pressure gauge (Replaced a stuck sendor year or so ago.)