Useless "oil pressure" gauge

Broeheem · Sep 16, 2016

Dear TRS.... thank you. I was smashing champagne glasses and peeing on the floor, trying to figure out what the issue was with my oil pressure "gauge" (1990 4.0) reading a constant "middle" no matter the engine RPM (turn the key....click *POING!* middle). Thanks to the extensive info on these pages, I've now learned that it isn't really a gauge at all.... more of a sophisticated "dummy light". Thanks for that, Ford. Pretty weenie if you ask me.

There is a fix, involving bypassing a 20 ohm resistor on the back of the cluster, and replacing the "oil sending unit" with a real one. Unfortunately, I have no clue where to source the "real one". If you know....

Now, if I can figure out the wonky fuel gauge that can't seem to decide my fuel level..... gotta wonder now...... is that a FakeyFord "gauge", too?

ericbphoto · Sep 16, 2016

I got a pressure sensor from Rock Auto and used an aftermarket guage . It's pretty simple.

Your fuel level issue might be the sending unit in the fuel tank. I had an '88 F150 years ago, on which both fuel level sending units went bad. I never replaced them. Just used the trip odometer to keep track of when to fill up.

Sent from my SM-G920V using Tapatalk

RonD · Sep 16, 2016

Google: oil pressure PS60

That's the standard Ford oil pressure sender

This article has the dash wiring required: http://www.rowand.net/Shop/Tech/FordOilPressureGaugeFix.htm

Nothing wrong with using an oil pressure switch, I do get why there are complaints about hooking it to a gauge, but 95% of drivers don't care.
And low oil pressure is when you get valve train noise, anything above that is great oil pressure, so 4psi or higher on most engines.
Most don't understand what oil pressure is, it is oil the engine CAN NOT USE, it is back pressure from oil that can't be sent thru the main passage because engine is currently getting enough oil and can not use any more.
Now you definitely want oil pressure, having too much oil is way better than not enough, lol, but 6psi or 60psi is still too much oil so both are OK as far as engine lubrication and cooling.
High oil pressure will cause dry spots on the bearings as oil squirts thru, so high pressure is as bad as low pressure, actually worse since it usually occurs at high RPMs, so very fast failure.

While dash is out check the Anti-slosh module
Google: Ford ranger anti-slosh module

This module keeps the gas gauge needle from going up and down every time you go around a corner and gas sloshes around in the tank.

As said above it could also be the float/sender in the tank.
You can use an OHM meter to test the sender and then add some gas and test it again to see if OHMs are changing

ratdude747 · Sep 16, 2016

I wrote an article on this:

http://www.therangerstation.com/forums/showthread.php?p=1573792

That should be a start. Unless you already read it... Look near the gauge for the resistor... If you're lucky it will be labeled.

adsm08 · Sep 16, 2016

Dude, instead of throwing a hissy fit that Ford put in a dummy light that gives most people the information they need (good or not good), but won't cause crazy people (reads "Most of population) to think there is something wrong when there isn't, maybe consider installing a mechanical gauge.

Broeheem · Sep 16, 2016

"Ericbphoto" - I already installed a new fuel pump/sender, tested the ohms

"Ron D" - I already poached a few anti-slosh modules from the wrecking yard - you can see on the old one where it's burned, an unburned one woke my gauge up. Before, it just stayed on [e], now it always pegs at [f] at startup, then jumps around from there. Start - 3/4, drive for 10-15 miles, shut off, start - 3/8. Start again - 3/4.

"Adam08" - The "hissy fit" is born from the fact that most would expect a guage to have varied readings as opposed to the "on/off" information supplied with this one. The fact is, almost no car sold today even has an oil pressure gauge, but I stand by my opinion that if it does have one, it ought to function like a gauge. I don't much want an aftermarket gauge when the actual gauge in the cluster can be made operable if I can source the appropriate sending unit. With that and bypassing the 20ohm resistor, it will.

RonD · Sep 17, 2016

Fuel gauge is powered by a Pulsed 5volt power supply behind the instrument cluster.

The sending unit in the tank is a variable resistor(variable OHMS), like a light dimmer or volume control.
Sending unit is the Ground for this circuit.
So this is the circuit:
5volt-----------gauge---slosh module------------------(yellow wire)----------sender-----Ground

So basically this is an OHM meter, and the gauge shows the OHMS(resistance) that the sender is at, which is set by the float moving in the tank.

1989 and up Ford gas gauge's use a sender that will show approx. 16 OHMS when float is at the bottom of the tank, EMPTY.
And 160 OHMS when float is at the top, FULL

Good read here on this gauge: http://www.fordification.com/tech/fuel-sending-units.htm

The easiest thing to do is to test Sender first, take it off the table as the problem or ID it as the problem.

You can test it by pulling dash again and use OHM meter on that Yellow/white stripe wire, to test for stable OHMS to Ground.
Or you can do the same at the connector under the truck, although that does not test the whole yellow wire to the dash.
If that yellow wire has rubbed thru some where then it can Ground itself, which would show EMPTY on gauge while it was grounded.
So best to test whole wire for stable OHM reading

You can also test power supply at that time.

Useless "oil pressure" gauge

Broeheem

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