oil pressure sender for working gauge?

[Raser13]

hey guys i've just recently found this site, and just starting to fix up my trusty truck. it's a 91 ranger basically fleet truck with the four banger. while doing some reading on the net looking for pin outs for a tach gauge swap, i found out that our oil pressure gauges have been rendered useless by ford. basically made into idiot lights. wtf? why would they do this? just to get more motors to blow up?

any way, i did see that there is a way to undo this and make them work by jumping the resister and replacing the switch with an actual sender. the walk through i saw was for a newer F250. and they didn't say what sender they used to replace the switch. anyone know for what vehicle i would need to ask at the parts place to get the right sized sender to fit where mine is? or better yet a p/n?

i like having more gauges than less. hence the tach cluster swap. it would be stupid to go through all that work and then have the pressure gauge just be an idiot light. thanks for any help you can render.

 

[tomw]

All of the sending units I have seen for oil pressure gauges appear to have a 'dome' that allows room for a variable resistor 'sweep' inside. If you ask for a sending unit for a 1990 Mustang 5.0, you should get one that would work. You may have to do some 'plumbing' to make the sender fit, such as extensions and elbows. The 5.0 required an extension, from memory, that was hex-shaped, pipe fitting male at one end, and female, at an angle, at the other end. You can more or less make up whatever you want to position the sender so it does not interfere with anything else.
In addition, you could check for a SVO turbo Mustang sending unit, or a Turbo T-bird. They both have 2.3 Lima's with sending units, from memory. I don't *think* they had the fake-out installed in later trucks/cars.
tom

 

[RonD]

PS60 Oil Pressure Sender is what you want, along with the gauge bypass wire.

Good how-to here: http://www.rowand.net/Shop/Tech/FordOilPressureGaugeFix.htm

You need to solder a wire to by-pass resistor or solder the circuit board connections that have been cut, either does the same thing, it takes the resistor out of the circuit.

Around the mid 1990's Ford switched gauges so the resistor is inside the gauge, as far as I know these can't be modified to use a sender


The change to the oil pressure switch was done so gauge wouldn't cause driver concern until there was a problem.
The oil pressure switch is Closed(ON) when oil pressure is above 6psi
Oil pressure switch is open(OFF) when oil pressure is below 6psi.
The 20ohm resistor is needed so gauge will read above 0 and below 1/2 when switch is closed(pressure above 6psi)
Yes, it is the same as an idiot light but in fairness not alot of people know or care about exact oil pressure psi.
No oil pressure = bad
above 6psi = good

With a "real" oil pressure gauge it would still read oil pressure below 6psi, so driver may not think there is a problem, with the idiot light gauge it would show 0 oil pressure and that should alert driver that something needs to be checked.
Generally you will get valve train noise at about 3-4psi, main and rod bearings would still be fine at this point but could start heating up a bit, so the idiot light gauge does serve a purpose.

Oil pressure is UNUSED oil, it is back pressure that represents the amount of oil the engine can't use.
At idle oil pressure is lower, rule of thumb is 1psi per 100rpms, so 600rpm idle should be 6psi oil pressure.
As rpms increase oil pump pushes more oil into the system, but bearing gaps and other passages are still the same size, so the amount of un-usable oil goes up, back pressure increases.
Above 6psi is all that is really needed, it is enough pressure to push oil to the top of the engine, valve train.
High oil pressure can be a bad thing just like low pressure, it can cause a "washing" of bearing surfaces causing wear and then failure.
This would be the reason for a "real" oil pressure gauge, but it doesn't happen that often, oil pumps pressure relief valve would need to fail closed, rare occurrence, but not a never occurrence

 

[Mac]

I used sender PO6091 and followed close to this write-up.
Dave
http://forums.tccoa.com/37-work-progress/75977-how-convert-your-oil-pressure-gauge-pics.html