Oil pressure

I've got a 94 ranger and every time I start the truck the oil gage doesn't come up as far as it did the day before. It to the top of the checkered with valvoline Max life and a Fram tough guard filter. It used to be dead center of the gauge and not its over a quarter of the way to the low pin. Is this normal?

Is it burning/using oil ?Check the connection on the oil sensor, over time can get loose.

In the mid-'80's Ford changed to an oil pressure SWITCH on the engine, so no sender.
The switch is "open" if oil pressure is 0 to 5psi, "closed" if oil pressure is 6psi or higher.
This is a 1 wire setup, the threads of the switch are grounded to block.

The switch is the Ground for the dashboard gauge, sender was as well but it was a variable ground, so gauge needle would move as oil pressure changed.
The switch means any movement of the needle is an electrical change not oil pressure change, outside of above or below 5.5psi.
Reving engine and seeing needle move means alternator voltage is changing, I am sure oil pressure is as well but that is not what you are seeing in that needle movement, it is an ON/OFF switch.

On the back of this type oil pressure gauge setup there will be a resistor, the value of this resistor sets where the needle will be when switch is a ground(closed).
The resistance in this resistor or the wire may have changed and needle is at a different location.
Or the power to the gauge is lower, corroded connector or wire.

So yes this can be "normal" as wiring and truck get older.
If needle was dropping to 0 at warm engine idle then that would be a concern, pressure would be below 5psi, you would usually get valve train "ticking" when pressure got down to 4psi or so.

Remove the wire from the switch on the engine, then ground that wire.
Turn on the key and and see where needle sits, if it is back to what you are used to then replace the switch.
If it is at it's "new" location then problem is in the wiring, gauge or power.

You can change pre-'95 oil pressure gauges to "real" pressure gauges by removing the switch and installing a PS60 sender on the engine.
And then removing the resistor on the back of the gauge.
In 1995 I think Ford built the resistor into the gauge, so not easy to convert.

Thanks! Anyplace will have that sensor to replace fords dummy light gauge idea?

Yes, the SENDER is a standard PS60, which is a universal sender that works with Ford gauges once resistor is removed.
You may need an adapter or elbow, as the PS60 is wider than the switch.

Have a look here: http://www.rowand.net/Shop/Tech/FordOilPressureGaugeFix.htm

I don't agree with the writer of the article but the pictures are good
Monitoring "real" oil pressure is not something 98% of drivers do, changing it to an ON/OFF setup was done to stop 1% from worrying about low gauge pressure and spending money trying to fix a problem that doesn't exist, the other 1% know that anything above 5psi at idle is fine to cool and lube the whole engine.

If a low oil pressure problem should occur, below 5psi, then this gauge reads 0, even my wife "might" mention that to me, "The oil pressure is at 0", might being the key word, but it is certainly more of a possibility than "The oil pressure needle seems lower", that I know she wouldn't notice or mention, lol.


Oil pressure is the unused oil that is backing up in the passages and filter, it is back pressure that builds up because the oil pump is pushing more oil than can be used into the filter and oil passages.
Some pressure is good and needed, upper part of the engine needs at least 5psi in the lower part to get good flow in the upper part.
Too much pressure is bad as well, oil coming out at bearings at a high pressure can cause a cavitation effect and bearing gets hot spots causing failure.

I did the sender mod on my 1995 with a 3.0 awhile back. The sender was $13 at rockauto (and that was a geniune motorcraft unit). A few tips and pics (Should I submit this with details as a tech article?):

-First, when you fit the sender, if you have an automatic, you'll need a 45 degree street elbow to clear the fill tube. The only place that sells them brick and mortar is Rural King (at least around here). You will also need to nudge the fill tube a bit to get the socket to fit when removing the old switch.



-There is a 20 ohm resistor on the back of the instrument cluster that will need to be shorted. I did this by soldering a wire to the resistor's crimped pads; however, IIRC, there also are some bare pads (test points?) nearby that can also be solder bridged.



The only issue I've found is that my needle randomly bounces a lot... although that could be my motor having an issue (which has 130K and I have evidence that it was formally abused- lack of oil changes).

Very nice pictures, yes I would like to see this added to Tech Article Section

The PS60 sender, like the switch, uses the engine block as it's ground, so you need to make sure to leave a few threads of bare metal on the elbow, adapter and sender to get a stable ground.
If using tape or liquid sealer leave lower threads bare.

Another tip: to turn in the street elbow with the engine still in the truck, the only thing that worked was a 1/2" drive king gator grip socket.

I've found that the teflon tape isn't an issue. The thread edges cut it when tight (as the tape doesn't seal, it just reduces friction to allow for a suffiently tight fit of the tapered threads or so I'm told). The sensors have the teflon from the factory anyway, so the only tape needed is for the street elbow.

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I'll work on a tech article submission. There's a few pics I'll want to shoot first... luckily I still have the old switch and the box to the new one.