OK I'm new to these pages but on my second Ranger..hehe. So driving home last week, up the Ol' Maine Turnpike, I watched the oil pressure gauge on my 91 Ranger, 2.3L, 2X4 with 111k miles, drop to nothing. Well you know what pucker'd . So I pull off and check the oil, hmmm its full. This weekend I put in new oil pressure switch and change oil and filter. Using Castrol 10w30 and a Fram filter. Well pressure comes up but soon as "normal" temperature is reached and engine is at running speeds, the pressure drops to nothing again, stop and idle, pressure goes back up. So tomorrow I'm going for a mechanical gauge setup and see what the oil pressure is really doing. But I'm wondering about 2 things here, 1). I have a "low oil sensor" in the side of the pan, could that have an effect on the gauge? 2). I pulled the wire off the pressure switch and grounded it out only to discover that the gauge only goes to the middle of the "NORMAL" range, this didnt feel right, I figured it would peg the gauge. Any suggestions from you ranger Vets out there? And can the oil pump be changed without pulling the motor?

 

Hey there Murdock welcome to FTE! I experienced a simular senario with my 91 ranger 2.3 about 3 years ago (about 100K miles). I was on my way to New Mexico when my oil pressure dropped, so I pulled off and shut off the truck. After a little time had passed I tried it again and pressure was up but that lasted for only a little while. This went on several times before I finally said to heck with it and finised my trip. I was going to be spending a little time in West Texas so I decided to try to fix the problem, what I found was the oil pump had sucked in the pan gasket. The gasket had been either sucked in a small piece at a time or was chewed up, any how the gasket was on the pump screen and was not letting the pump build enough pressure. Well we got the old pump off fairly easy but replacing it was a larger chore as it turned out we didn't quite pull the whole engine but we did have to lift it up so the oil pan would clear the cross member. After we lifted the engine the rest was fairly easy. I hope I have not brought you too much bad news and I hope yours is not this complicated. Keep us posted and good luck.

 

I am having the exact same problem. I have a 1990 2.3, auto. I was driving up a grade and suddenly lost all pressure (according to the gauge). I pulled off the freeway, shut it down then checked the level, it was full. I had just changed it a few days before. (10-40W with a puralotor filter) My truck only has 40K miles on it. When I restarted the truck, it seemed noisy, so I assume I really lost pressure. After letting it cool down, I tried it again, I got pressure back, but as soon as it warms up and I give it any gas, it drops right back down to zero pressure. I changed the filter to a Motorcraft and tried it again and same result. I have pressure at idle or slow speed, as soon as I give it any gas it drops back to zero. I looked at my oil pan and mine has a plate that looks like you can remove from the pan. Can I replace the pump through this opening? I sure don't want to have to drop the pan if I don't have to. What do you think is the problem?
I can't imagine an oil pump would be intermittent like this. I would greatly appreciate any help. I am baffled and fustrated! I love this little truck! Thanks

 

I certainly have no crystal ball that would allow me to see into your guys oil pans, but I would have to seriously question whether there was some form of faulty pressure relief valve in this circuit.

FWIW - and I have no idea whether such a valve exists in your engine.