Hello All,
This is my first post. I've read prior threads concerning oil pressure, but I would like a little clarification. I run a 1990 Ranger with a 2.9 six as my daily driver. A few years ago the oil pressure gauge started to fluctuate so I changed the sending unit. This helped, but the pressure would still fluctuate. It wouldn't drop to zero, but it would still move up and down the gauge. Lately, the gauge has been reading low enough that I've started to worry. Last week, about 300 miles ago, I changed the oil. I used a quart of engine flush before the change. The oil change did not have an effect on the gauge. Today on the way to work, the gauge fell to zero. It stayed there for about 5 seconds while I was doing about 60mph - no unusual noise from the motor. When it did move from zero it didn't move far. When I pulled in the parking lot the gauge read zero. I sat in the running truck for about 20 seconds watching the gauge and listening to the motor. Again there were no unusual noises coming from the motor and eventually the gauge bounced up to normal.
My questions are, does this sound like a sending unit problem, or an oil pump/screen problem? If the sending unit fails does the gauge bounce around or should it just read zero? Can I drop the oil pan on the 2.9 without lifting the motor? Is there an oil viscosity that could help?
Obviously, I'm hoping the problem is with the sending unit. Even if the acutal pressure is okay as long as that gauge is reading so low I'm a nervous wreck while driving. If I simply disconnect the wire from the sending unit would my gauge read zero all the time? I think I might prefer that to watching it bounce around.

Thanks.

 

I would begin the diagnosis by hooking up a mechanical oil pressure guage that is known to be accurate.

 

welcome to the board.
sometimes the stuff you stick in the system to flush it will jam up the sender units, but as soon as possible i would check the system with a "real" oil guage just to make sure. Usually when you have 0 oil pressure the motor will sing a very sad song

 

Thanks for the replies. Am I correct in assuming I could purchase a mechanical gauge and connect it where the sending unit screws in?

 

I'm thinking clogged screen, connect it there.

 

Ken,
When you say "connect it there", where do you mean?

 

Sorry about not being clear, I was getting ready to leave work. I meant to connect it were the stock sending unit is, you were correct.

 

I'll hook a mechanical gauge up this weekend, but assuming I do have a clogged screen, can I drop the pan without lifting the engine. Additional info that may be relevant - It's a 2WD auto.

 

The book says you can do it on a 2wd by just jacking the engine up a bit but everyone I've talked with says its MUCH easier to pull the engine out.

 

Thanks for the information. I also have a Haynes manual that says I need to pull the motor, but just looking at the oil pan, it appears that I could get it out without pulling the motor. Getting it back on could be a different story. I've never pulled a motor and frankly wouldn't know where to start. Does anyone have any first-hand experience removing an oil pan from a 2.9 2WD?