When I cold start, the oil pressure needle is pegged. As the engine warms up, the oil pressure gauge goes to a normal range reading and the temp needle pegs. Scan gauge has coolant temp at about 160 - 170 when they switch places being pegged. Any ideas on where to start on this one?

 

Find the pressure sending unit. Is it a big round can or a small looking switch? Whichever it is, it should have a single wire going to it.

 

I just went out and cold started it again as I was curious to watch the gauges as it warmed up. Oil pressure high to start, and as temp increased, just after needle came up into the bottom end of "normal" operating range, the temp needle pegged and the oil needle dropped to where I'd expect it normally.

I haven't tried to locate the oil pressure sending unit yet. What am I doing with it once I find it?

 

You can leave the engine off but turn the key to run, pull the wire off the sending unit, and ground the wire and watch the gauge, and then let the wire hang in the air and watch the gauge. If the gauge swings back and forth full scale when you do this, then it's probably ok. You can find the temp sensor and do the same thing to watch the gauge for it. It's a single wire unit also. You may find a two wire temp sending unit, that is for the engine computer.

The reason I ask about the shape of the oil pressure sending unit; Starting sometime in the late 80's Ford had the great idea to make the oil pressure gauge what I call a "pseudo" or "fake" pressure gauge. The early units had a large round can with a variable resistance inside that made the gauge move according to the oil pressure. These later fake gauges are just hooked to a regular oil pressure switch. They installed a resistor on the cluster circuit board to make the needle ride in the middle.

You can tell if you have the fake gauge by looking at the sending unit. It will be very small, looking like a common oil pressure switch that turns on a idiot light(because that's what it is). No oil pressure, the oil pressure gauge reads 0 or low. Over 5 lbs of pressure, the guage reads in the middle. 10 lbs, 20 lbs, 30lbs, etc. the guage always reads in the middle because that's where the resistor holds it.

When you find this out it really is a waste of time to even get it working. A aftermarket set under the dash will give you real readings.