Maybe an easy question about guages (1 Viewer)

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From F.5 on, the oiling is different. So, someone with a '73 engine typically sees an oil pressure drop as it heats up, and the oil pressure goes up on a 2F when the engine gets to temperature. The F doesn't waste much oil pressure on running it thru a cold filter, it is bifurcated and it easily flows thru the engine, all leftover pressure is for filtering. The 2F must pump all its oil thru a fine fine fine media, which is very difficult at startup or when the oil is too viscous, after it gets warm, it has more oil going thru, and therefore more oil pressure where it is read by the sender unit.

My suggestion is to install a Denso filter on the engine in question, just to be on the same page as more of us, and because the Wix has a bad reputation on forum threads, and because it is not expensive and easy to do without changing the oil. I wouldn't toss it, just wipe it down, and cover it with plastic wrap to keep dust off of it stored with the threads up, if you want to see how it affects things. Most people that I've encountered suggests that your choice of filter doesn't affect oil pressure, but, it seemed to make my needle lean right. There are huge differences in the medias and internal volumes of these filters, so it makes sense to me, plus they all have some kind of pressure release valve psi rating, but the info is largely hidden.
 
In an interesting turn of events, this reading is with the key turned power but not started...🤔

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That gauge is FUBR
 
The gauge or sender. Ground the wire at the sender and see if the gauge goes from 1 end to the other.
 
The sender is screwed into the engine blk which grounds it. With the key on, the guage wire supplies power to the sender. The oil pressure pushes on the sender and the gauge measures the resistance created by the sender between wire and ground. So a basic test, Pull the wire off the sender. Turn the key to the on position. Now touch the wire to a ground. Usually the block is sufficient. You're fooling the gauge and the needle will make a full sweep because the there is no resistance. Ground it long enuff to make the full sweep. Dont keep it grounded. If the gauge needle makes a full sweep, it's probably the sender that's bad, if it doesn't then it's probably the gauge. Or refer to fsm for a more detailed diagnosis, you'll likely need a multimeter.
 
The sender is screwed into the engine blk which grounds it. With the key on, the guage wire supplies power to the sender. The oil pressure pushes on the sender and the gauge measures the resistance created by the sender between wire and ground. So a basic test, Pull the wire off the sender. Turn the key to the on position. Now touch the wire to a ground. Usually the block is sufficient. You're fooling the gauge and the needle will make a full sweep because the there is no resistance. Ground it long enuff to make the full sweep. Dont keep it grounded. If the gauge needle makes a full sweep, it's probably the sender that's bad, if it doesn't then it's probably the gauge. Or refer to fsm for a more detailed diagnosis, you'll likely need a multimeter.
Ok, so before, I only had the oil guage wire connected to the purple, came on with any power. Then moved to the red and nothing moved, didn't work. And now I have oil wire to the red going to guage and made dedicated ground from purple. And nothing moved at all ..
 
Well, Haynes says to ground the oil pressure gauge sender lead thru a 3.4W bulb, not directly to ground.
Umm.

So use a test light. Like I said it's a quick test. Your looking for a reaction of the needle to confirm the gauge is working. Don't keep it grounded.
 
Ok, so before, I only had the oil guage wire connected to the purple, came on with any power. Then moved to the red and nothing moved, didn't work. And now I have oil wire to the red going to guage and made dedicated ground from purple. And nothing moved at all ..

I looked at the 71 wiring diagram on coolermans websight and shows a yellow wire supplying power to the gauge and a yellow wire with a blk stripe going to the sender.
 
Sounds like the gauge is suspect. If the key was on and no movement or full sweep of the needle when the y/b wire is grounded. Do you have the cluster out? When removing the cluster, the wires on the amp meter are hot. You don't want them to ground. You might want to disconnect the batt while taking it in and out. Do you have a multimeter? Once the guage is out reconnect the batt, key on, and confirm you have power on the yellow wire. Now with the key off, Check ohms across the gauge terminals. According to my 74 fsm you should get 44 ohms. Do you have a test light? You can check the sender , disconnect the wire at the sender, connect the test light to the +batt and touch the senders terminal with the engine off. The light should be off light, and it should flash with it running.
 
Sounds like the gauge is suspect. If the key was on and no movement or full sweep of the needle when the y/b wire is grounded. Do you have the cluster out? When removing the cluster, the wires on the amp meter are hot. You don't want them to ground. You might want to disconnect the batt while taking it in and out. Do you have a multimeter? Once the guage is out reconnect the batt, key on, and confirm you have power on the yellow wire. Now with the key off, Check ohms across the gauge terminals. According to my 74 fsm you should get 44 ohms. Do you have a test light? You can check the sender , disconnect the wire at the sender, connect the test light to the +batt and touch the senders terminal with the engine off. The light should be off light, and it should flash with it running.
I have a meter, I will check it tomorrow. I wonder how different these sensors really are, because the original 71 didn't have the oil cooler and this 87 2f has the cooler, which is probably why it needs a ground as it's not grounded to the block. I will check ohms tmrw and power
 
Sounds like the gauge is suspect. If the key was on and no movement or full sweep of the needle when the y/b wire is grounded. Do you have the cluster out? When removing the cluster, the wires on the amp meter are hot. You don't want them to ground. You might want to disconnect the batt while taking it in and out. Do you have a multimeter? Once the guage is out reconnect the batt, key on, and confirm you have power on the yellow wire. Now with the key off, Check ohms across the gauge terminals. According to my 74 fsm you should get 44 ohms. Do you have a test light? You can check the sender , disconnect the wire at the sender, connect the test light to the +batt and touch the senders terminal with the engine off. The light should be off light, and it should flash with it running.
I have 12v to both guages, My fuel guage works. I will check ohms from the sensors
 
Sounds like the gauge is suspect. If the key was on and no movement or full sweep of the needle when the y/b wire is grounded. Do you have the cluster out? When removing the cluster, the wires on the amp meter are hot. You don't want them to ground. You might want to disconnect the batt while taking it in and out. Do you have a multimeter? Once the guage is out reconnect the batt, key on, and confirm you have power on the yellow wire. Now with the key off, Check ohms across the gauge terminals. According to my 74 fsm you should get 44 ohms. Do you have a test light? You can check the sender , disconnect the wire at the sender, connect the test light to the +batt and touch the senders terminal with the engine off. The light should be off light, and it should flash with it running.
Ok, so I don't have a test light but I have a meter. I checked per FSM guage post A to B and getting 45 ohms. I get 12v to guage when it's plugged in. So I'm reading the fsm and it only describes testing the sender via light. Is there a way to test my senders with a meter? Is there something else I'm missing?
 
Ok, so I don't have a test light but I have a meter. I checked per FSM guage post A to B and getting 45 ohms. I get 12v to guage when it's plugged in. So I'm reading the fsm and it only describes testing the sender via light. Is there a way to test my senders with a meter? Is there something else I'm missing?

Whenever i run into 12v electrical issues or basic circuit diagnosis, the 1st thing I grab is a test light. It's a simple electrical circuit. Power in 1 end, a light doing work, and a ground. I can track down an issue very quickly. Grd one end and search for power. I typically use a multimeter if I need a value of volts, amps and ohms. You can buy a decent test light at any auto parts store. You want a decent one with a heavier wire, sharp point and good clip. The test described has more to do with how the sender works.
 

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