Oil pressure problem.

[HotWheelsAS]

I have a '92, 3.0L Aerostar.

Changed the oil/filter yesterday and was driving the van today when I noticed the oil pres. gauge start to fluctuate, shortly thereafter the needle dropped off to zero, reading no pressure. I pulled over and added more oil. When I started it back up, gauge went back to reading normal for a while, maybe 15-20 minutes, then fluctuated. Ran it later in the day and got basically the same thing. After a bit of running the gauge would fluctuate/drop off/come back.

During the whole process, I didn't notice any change in sound of the engine; it didn't sound like it was running rougher or knocking or anything. I'm guessing if I actually had no oil pressure, I would have heard it, right?

New oil, new filter. Is it a coincidence that this happened the day after I changed them? Does it sound like a gauge/sensor thing? (/if it's a sensor how do I find that? Under the hood? Doghouse?)

Finally, is gauge fluctuating a sign that if I drive the van it WILL lose pressure, it just hasn't yet? Or might it be pretty safe to assume it's sensor/gauge thing? Thanks for everything. -Chris

 

[don-ohio]

Did you check the oil dipstick to make sure you filled it? Did you start it up after filling it and look for leaks under it? Make sure not to use any oil less than 10W30 in it unless you live way north.
If it is leaking, the oil plug may not be tight, OR as has happened to me, the old gasket from the old filter might've stuck on the base and that'll cause a bad leak. Make sure the old gasket is still on your old oil filter.
Main thing is check that oil level with the dipstick on pretty level ground. don-ohio ^)

 

[BrooklynBay]

Clean or replace the sending unit. It might be full of dirt or sludge from oil.

 

[92exp4x4]

Does the 3.0L have a sender or a switch? I'm nearly positive its a switch. Most of the Fords in this era had pressure switches. The gauge really isn't a variable gauge. Its designed to read one reading or nothing based on a minimum pressure, which is only about 8 PSI. Check the wire connection at the sender/switch and make sure there is no corrosion. Clean it and make sure its good. You should see an improvement. Also, crap in the passage can cut oil pressure getting to the switch and cause a bad reading.

There are mods you can do to make a real gauge if you want that. Search the forum as people have done write ups for this very thing.

 

[Josh P]

Did you use a fram oil filter? The oil pressure relief bypass valve is cheaply made will cause the oil pressure to fluctuate. Modifying the cluster to read psi is easy once you get the dash apart. There is a 20 ohm resistor on the back of the cluster you short and if you shop at napa the sending unit part number is OP6091. My jeep grand cherokee did the exact same thing showing no oil pressure, warning lights on the dash. I freaked out that I lost the oil pump or something. Turned out to be the oil psi sending unit, it was leaking oil out the electrical plug down the side of the engine. If you had no oil pressure you would know it real fast, the engine would be ticking.