Oil sending unit - odd wires on it

[kenn]

I ordered a new oil sending unit as my pressure reads very, very high. As soon as the accessory lever is switched on, the pressure jumps to about 10psi (motor not yet running). On starting, the pressure gauge jumps to about 60 mark (0-120 gauge) and after a moment settles around 90-100 or so. I assume it is a 0-60 sending unit on a 0-120 gauge but I can't tell as it is covered in heavy green paint.

The new unit arrived and I have yet to replace it (waiting on a fitting for coolant related job) but on taking the old one out, I noticed a couple of things I've not seen before. At the tip, there was a small piece of wire and my heart sank until I realized that small piece of wire is captured. It spins around in the tip and cannot be pulled out. The second thing is there is a wire of some sort attached to the side of the sender that may at some point have been soldered to the side of the unit but there is heavy paint still where it would have been attached and there is definitely a gap now.

Question is, what are these and why are they there on the original oil sending unit?

*** EDIT *** I was taking pictures of it from various angles and found some faint indentations in the paint! It is MS24538-1 and I found a big "60" under the paint so I'm pretty sure this is a 0-60 on a 120 gauge and therein lies my reading problem. I'm still curious about the wires, though!

 

[Guyfang]

Indeed, MS24538-1 is a 60 PSI switch. Most things it fits on has tracks, like M60. M88, M109 and so on.

 

[ToddJK]

I ordered a new oil sending unit as my pressure reads very, very high. As soon as the accessory lever is switched on, the pressure jumps to about 10psi (motor not yet running). On starting, the pressure gauge jumps to about 60 mark (0-120 gauge) and after a moment settles around 90-100 or so. I assume it is a 0-60 sending unit on a 0-120 gauge but I can't tell as it is covered in heavy green paint.

The new unit arrived and I have yet to replace it (waiting on a fitting for coolant related job) but on taking the old one out, I noticed a couple of things I've not seen before. At the tip, there was a small piece of wire and my heart sank until I realized that small piece of wire is captured. It spins around in the tip and cannot be pulled out. The second thing is there is a wire of some sort attached to the side of the sender that may at some point have been soldered to the side of the unit but there is heavy paint still where it would have been attached and there is definitely a gap now.

Question is, what are these and why are they there on the original oil sending unit?

*** EDIT *** I was taking pictures of it from various angles and found some faint indentations in the paint! It is MS24538-1 and I found a big "60" under the paint so I'm pretty sure this is a 0-60 on a 120 gauge and therein lies my reading problem. I'm still curious about the wires, though!

I'm not sure what does what exactly, but mine looks a bit different as I do have the 0-120 sending unit and it just has a plug to it. Is the new unit a 0-120? If not, it'll be off again, maybe just not as jumpy, but if it is and it still flickers around a lot, I would check the wires to make sure it's in good shape and perhaps look into a new gauge. Nice thing is, even if the gauge is correct and working properly, nothing wrong with an extra, but also they aren't hard to sell as there's always someone needing one as it seems.

 

[kenn]

I'm not sure what does what exactly, but mine looks a bit different as I do have the 0-120 sending unit and it just has a plug to it. Is the new unit a 0-120? If not, it'll be off again, maybe just not as jumpy, but if it is and it still flickers around a lot, I would check the wires to make sure it's in good shape and perhaps look into a new gauge. Nice thing is, even if the gauge is correct and working properly, nothing wrong with an extra, but also they aren't hard to sell as there's always someone needing one as it seems.

Thanks, Todd! I got a 0-120 sender so it would be aligned with my gauge. I got it from Big Mikes and is as yours -- single plug and sensor without oddball parts.

I found a picture of a very old sender that had a wire sticking up from the side and also not connected. I have to assume then, that this wire wasn't some sort of afterthought resistor trying to make it act like a 0-120 -- especially since where it starts and where it would attach wouldn't do anything.

 

[ToddJK]

I don't know why that has that wire like that, unless it was a thought that it would be used on more than one type of motor, or a ground, but I don't know why those old ones have it while any of the newer ones we see today, do not.

 

[G744]

That is not an electrical wire, it is a pipe used in the sealing process making the sender.

Kinda' like those found in air conditioners' Freon lines.

Leave it alone.

DG

 

[kenn]

That is not an electrical wire, it is a pipe used in the sealing process making the sender.

Kinda' like those found in air conditioners' Freon lines.

Leave it alone.

DG

Thanks! What about the little captured 90 degree wire in the hole that spins freely? Something to keep the hole unclogged maybe? This is mere curiosity as I have a new sender and will install it shortly.

 

[G744]

The confusion comes from the fact that there is but one electrical wire connection. The other thing is as described previously.

You're also missing the rubber boot on the terminal of the first photo sender.

They are the same as on the wiring looms, available from several sources.

Just spin off the nut/washer and slip on a new boot. Reinstall the nut & washer.

DG

 

[kenn]

Alright. Well. I'm not sure where to go from here. I just put in my shiny new oil pressure sending unit from big mikes. It is labeled as a 0-120psi. My gauge is a 120psi. It should match. And work. I removed a 0-60 that would read about 10-20 psi when I flipped the lever (not started yet), jump to about 60 on start and after a few moments pretty much pegged to the right around 100-120psi. I figured the 0-120 would cut it in half and I'd be right as rain.

After installing, I put lead 36 on the sender and now as soon as I flip the accessory lever, it pegs at 120 before I even start the engine. This would be a test condition in the TM-20. Grrr.... "Ground lead 36 and if the gauge goes all the way to the right, the gauge is working and continue to the next test". The only thing I can figure is lead 36 has rubbed through and is grounding somewhere. I'll go over the wiring again...


*** EDIT *** I pulled 36 and put it back on again. I'm reading just over 45psi with the engine hot and idling around 1500. I'll keep and eye on it. I must have a loose connection somewhere.

 

[ToddJK]

Alright. Well. I'm not sure where to go from here. I just put in my shiny new oil pressure sending unit from big mikes. It is labeled as a 0-120psi. My gauge is a 120psi. It should match. And work. I removed a 0-60 that would read about 10-20 psi when I flipped the lever (not started yet), jump to about 60 on start and after a few moments pretty much pegged to the right around 100-120psi. I figured the 0-120 would cut it in half and I'd be right as rain.

After installing, I put lead 36 on the sender and now as soon as I flip the accessory lever, it pegs at 120 before I even start the engine. This would be a test condition in the TM-20. Grrr.... "Ground lead 36 and if the gauge goes all the way to the right, the gauge is working and continue to the next test". The only thing I can figure is lead 36 has rubbed through and is grounding somewhere. I'll go over the wiring again...


*** EDIT *** I pulled 36 and put it back on again. I'm reading just over 45psi with the engine hot and idling around 1500. I'll keep and eye on it. I must have a loose connection somewhere.

Check inside that plug from #36. Sometimes the wire breaks free inside that plug and is just barely making contact. It's pretty easy to pull apart and re-user the plug with new wire. I've also had the opposite side, near the gauge, so dry rotted, as soon as I lightly tugged, it just broke right off about a 1/4" from the plug.

 

[Guyfang]

Before the Edit, I was going to suggest making sure the gauge is wired right. Still might be a good idea. But if it works sometimes, and others not. Sounds like a loose/broken wire.