Ok......This is what I found from an explorer forum. It tells you everything you have to do to make your oil pressure guage fully functional. This was done on a V8 Mountaineer. But you get the idea....
I'm a firm believer in knowing what my engine is doing. I think you can never have too many gauges either. (Turning my Mountaineer's dash into an airplane's dash would be A-OK) But the gauges must work for them to be usefull. The stock oil pressure gauge in stock form is nothing more and an idiot light - it points sky high as long as there is about 5psi oil pressure. It reads low if there is anything less. However, there is a cheap, but time consuming fix.
Many members have posted how to convert the stock guage into a real oil pressure gauge, which shows fluctuating pressure. (Normal - and vital to undertanding the health of the engine) All of these posts have been for the OHV V6. I found that the V8 is slightly different - and a more time consuming install compared to what other members have reported.
1) Neihoff F133 Sender, From a 1987 F150 5.0. $5.99 Autozone
2) 1/4" Brass coupler $0.39 Home Depot
3) 2" 1/4" Brass pipe, $1.00 Home Depot
4) Teflon Tape
5) RTV sealant
6) short length of wire, 2 butt splices and heatshirnk tubing
7) 1qt ATF (for powersteering system)
8) PB blaster for stuck/rusty bolts
Special Tools needed:
1) 1 1/6" DEEP DRIVE socket
2) 10" extension
3) U-joint for socket
Once all of the tools and parts are gathered, give yourself a full day to get this job done. It may help to have an extra vehicle nearby to run for parts.
This is the method I chose to install the sender. There may be a better method, that involves less cuts and scrapes. Be carefull when working on your truck, but have fun and be creative
Part One: In the Engine Bay
1) Remove wheel well liner
2) Remove the reservoir-P/S cooler power steering hose from the small cooler. Drain the P/S reservoir.
3) Remove the battery
4) Unbolt the battery tray, (3 13mm Bolts) and disconnect any hoses/wires from the battery tray.
5) Remove the 10mm nut holding the powersteering hoses to the side of the A/C compressor. Route high pressure P/S hose out of the way. Disconnect low pressure hose from reservoir, and pull out of truck.
6) Disconnect green electrical wire from current oil pressure switch
7) Use 1 1/6" deep drive socket, u-joint and extension to remove the oil pressure switch
8) grab lunch - you're halfway there.
9) Assemble new oil pressure sending assembly. Use one layer of teflon tape on all threaded joints, as well as a THIN layer of RTV sealant. You don't want it to leak, but the electrical ground travels through the brass pipe. Make sure everything is tight.
10) Insert assembly into block hole. It may help to have a partner guide you by looking into the wheel well, while you stick you hand down the hood.
11) Use a 9/16" wrench on the base of the sender to tighten up the works. This process really requires patients and contortions. You will get scraped hands from the fanblade, but hey, no pain, no gain.
12) The old electrical wire is too short. Remove it from the block by undoing the two clips behind the upper serpentine idler pully. They just pull right off.
13) Crimp/Heatshirnk about 24" of 18 ga wire into the current harness. you want to keep the stock plug at the end. Rather than running down the front of the block, i chose to run down the side of the A/C compressor with the new wire.
14) Reassemble everything
15) Refill Powersteering system
16) Start the X up, check for leaks in both the oil and P/S stystems.
Part Two: Behind the Dash
The dash was removed as part of a mult-day project of replacing the stereo system and wiring in some Aux lights. Dash removal instructions by bigtigexplorer were followed. http://www.explorerforum.com/forums/...threadid=37017
Once the dash was out, I replace all of the 194 lightbulbs used for illumination.
Setbacks... Setbacks... what was supposed to be a ten minute solder job... wasn't.
On early model Explorers and Mustangs, to make the gauge fully functional, a 20 ohm resistor needs to be bridged on the back of the dash. However, my dash did not have this resistor. In mid 96, Ford stopped putting in real gauge armatures in Mustangs since they weren't putting in senders. It appears they did the same in my Mountaineer. So I'm stuck.
There are several options.
1) Do some hardcore electrical engineering to get my gauge working.
2) Tap into the sender, and run an external gauge, and leave the dash alone.
3) Go junkyard diving and get a 95-96 gauge cluster.
Many thanks to Maniak for helping me troubleshoot this problem. The diagnostics are taking place in the following thread:
I know some people have asked about the resistance values of the Neihoff Sending unit. I hooked it up to my air compressor before installing it on the truck.
0 psi = infinite ohms
20psi = 30.7 ohms
30psi = 28.5 ohms
40psi = 24.4 ohms
50psi = 21.3 ohms
60psi = 18.9 ohms
70psi = 17.1 ohms
The original ford unit is:
0 psi = infinite ohms
6 psi = zero ohms