mark_d

Hi all,
I just bought a 1991 F-150XLT Lariat 5.0l V8 and am trying to assess how well everything is working. Right now the oil pressure gauge is reading at the VERY low end of the "Normal" area, near the red line. I just filled it up with 20W-50 in the hopes of upping the pressure with a thicker oil, but no difference.

I know the old factory gauges are crap so before I sell into the 'low oil pressure' problem I want to hook up a mechanical gage and see if there really is any pressure. Problem is, I can't find the pressure sensor/sending unit. I read that it was located right behind the oil filter but I don't see any wires coming out of the motor near there.

Where is it? Thanks in advance!

unit505

Just above the oil filter towards the front of the engine about 2 inches.

KentuckyCountryBoy

You gotta take the ac compressor and ps pump off. It's behind that bracket. A few of us have used a brass tube and T fitting to hook up an aftermarket gauge and keep the stock sender. I used a 4in long 1/4in (I think) diameter NPT threaded tube with male threads on each end with a T on that with all female threads. It works perfect.

caprif150

not if you have the right socket.....

unit505

Do what? Did the 5.0 change from 91 to 94? The sending unit took me 5 minutes to change. No parts removal was necessary. Right there by the filter in plain sight. Maybe I'm missing something. I used a 27mm socket (I think). No big deal.

mark_d

Okay, well thanks for the quick though divided replies. I'm going to take a look tomorrow and see if I can find a place to get the socket.

I'll report back and let you know if I had to take anything apart.

KentuckyCountryBoy

Ok, you night not have to take that crap off. I found it easier to take it off cuz I was doing mods though.

unit505

Autozone sells the socket. Do not buy an oil sending unit socket! Waste of money. Get the new sending unit in hand, walk down the tool isle and fit the sending unit to the socket.

mark_d

I ordered a 27mm deep socket from Harbor Freight for almost nothing. It's pretty damn close to 1-1/16" (0.0125" bigger) and 1/5 of the price. Oil pressure tester was $19.99 which is tough to beat. I'll post when it's done. Thanks for the info

unit505

BRAVO! I find every reason possible to visit Harbor Freight. Might stop by there on the way home tomorrow. They are the MAN'S STORE! LOL