Oil Pressure Sender

[UNL1MTD]

If you aren't following along on my project page, I'm doing a gauge swap and having a problem with geting a reading on my oil pressure. I had the junk yard sender installed initially and got no movement on the gauge. I tested the gauge and when ungrounded it was far right and when grounded it was far left. Signs pointed to the sender being bad. I bought a new sender from auto zone and installed it today.

 

Well the needle moves ever so slightly when I crank the engine, but thats it. Perhaps some movement when going down the highway at 65, but reading no higher than 10. I think I may have another bad sender. The sender I received sounded busted. When I shoke it, it made a sound, like there was something loose/moving parts on the inside. The junkyard sender seemed solid, no sounds.

 

So my question is, should the sender make a sound when shaken?

 

Is it possible for the Mj to have this bad of an oil pressure and still run halfway decent? I know I have some oil leaks, which are on the list, but I can't imagine to have <10 psi on the gauge and operate.

 

TIA

 

-Sean

[Eagle]

Actually, they'll run on 10 psi, but you don't want to stress them.

 

Got a multi-meter? Test the sender. After the engine has been off for awhile, turn on the ignition but don't start the engine. Pull the wire off the connector on the oil sender, set your V.O.M. to the lowest ohm scale you have, put one probe on the sender contact and ground the other sender to the block. I don't remember which way it goes -- you should have a reading of either 0, or 88 ohms. I think it's zero.

 

Now start the engine and repeat. Have a helper rev it up a bit so you're getting highway speed type oil pressure. The max end of the scale for the sender is 88 ohms. Dunno if the scale is linear or logarithmic, but see if you're getting a reading of around 40 or 50 ohms. If so, the sender should be okay.

 

I would test mine, but I know it's off so I think it would provide an invalid comparison. Anyone feel like doing this test on theirs so we can get a few sample data sets? Check your oil pressure sender resistance at shut-off, at idle, and at 2000 RPM and report the results.

 

One other possibility is that the new sender is for an idiot light rather than a gauge. However, that's an on-off switch, so I would expect it to peg the needle as soon as the engine starts.

[johnnyc]

You're not using Teflon tape, are you? The oil pressure sender is a self-grounding unit, so there needs to be good metal-to-metal contact.

[BLHTAZ]

You're not using Teflon tape, are you? The oil pressure sender is a self-grounding unit, so there needs to be good metal-to-metal contact.

I was just wondering the same thing. I have seen that be a problem more than once.

[jtdesigns]

I can do an ohm test for you... give me a sec...

[jtdesigns]

ign on no start was 0 ohms Gauge= 0 psi

engine running at idle 7~8 RPM was hi/lo50~45 ohms Gauge= 40 psi

engine turning 2000rpm was hi/lo 59~55 ohms Gauge=43/45 psi

[Eagle]

ign on no start was 0 ohms Gauge= 0 psi

engine running at idle 7~8 RPM was hi/lo50~45 ohms Gauge= 40 psi

engine turning 2000rpm was hi/lo 59~55 ohms Gauge=43/45 psi

Perfecto. DATA!! We gots DATA!

 

That's a decent baseline for comparison. Thanks. (Of course, it's the lest you could do while the rest of us are slaving away here trying to steal an election for your main squeeze.)

[jtdesigns]

ign on no start was 0 ohms Gauge= 0 psi

engine running at idle 7~8 RPM was hi/lo50~45 ohms Gauge= 40 psi

engine turning 2000rpm was hi/lo 59~55 ohms Gauge=43/45 psi

Perfecto. DATA!! We gots DATA!

 

That's a decent baseline for comparison. Thanks. (Of course, it's the lest you could do while the rest of us are slaving away here trying to steal an election for your main squeeze.)

 

+ he got the sender from me... :roll:

[UNL1MTD]

Thanks for the help so far, all clean right now so I won't have a chance to test until tomorrow after work.

 

The sender is definitely for gauges, pn PS133 from autozone. It had some thread sealant on it, redish color, but I did not use teflon tape.

 

Any comments to the noise it makes/loose internal parts?

[jtdesigns]

Thanks for the help so far, all clean right now so I won't have a chance to test until tomorrow after work.

 

The sender is definitely for gauges, pn PS133 from autozone. It had some thread sealant on it, redish color, but I did not use teflon tape.

 

Any comments to the noise it makes/loose internal parts?

 

IDK man.. :dunno: Did they have anymore to compare??

[bobweiser]

For what it's worth, I have a brand new one in the box from NAPA and it doesn't make any noise when I shake it.

[Eagle]

That's still the old tin can style sender, correct? I don't recall those making any noise when shaken ... but I also don't recall using them as a substitute at a witch doctors' convention.

 

The factory replaced that tin can type with a different style that looks more like a black rubber cigar. I'm not suggesting that's any better, mind you, just different. Actually, the factory ones seem to have a high percentage of DOA right out of the box.

[jtdesigns]

That's still the old tin can style sender, correct? I don't recall those making any noise when shaken ... but I also don't recall using them as a substitute at a witch doctors' convention.

 

The factory replaced that tin can type with a different style that looks more like a black rubber cigar. I'm not suggesting that's any better, mind you, just different. Actually, the factory ones seem to have a high percentage of DOA right out of the box.

I got one of the rubber cigar ones off a grand with a 4.0,, it was a one wire deal, but it has a round spade on it..

The one I sent UNLIMITED is the tin can looking one.

[UNL1MTD]

right I got two that are tin cans, the rubber cigar one was 10 bucks more. I'll ohm both out tomorrow. Not liking the fact that it makes noise when shaken.

[camanchedriver23]

i bought a sunpro oil pressure gauge can anybody take pictures and tell me how to hook it up

[Eagle]

i bought a sunpro oil pressure gauge can anybody take pictures and tell me how to hook it up

Mechanical or electric?

[UNL1MTD]

Ohmed out the junkyard sensor from Jt. I tried to ohm out the new one, but I was doing so incorrectly. Instead of ohming to the block I was trying to do it passthrough. :headpop: In the process of trying to figure things out I switched back to the junkyard one.

 

Once I reread Eagle's post I ohmed out the junkyard one in the correct manner. Results:

 

Keyed on - 0-1 Ohm

Idle at 500- 700 RPM - 23-26 Ohms

1500 RPM - 42 Ohms

2000 RPM - 47 Ohms

2500 RRM - 50 Ohms

 

Hooked the gauge back up and had same results as before.

 

Never greater than 10 psi, some times less, some times more. I did notice a marginal amount of movement when I got the RPm climbing, but never more than 5 psi difference.

 

Its definitely putting out lower Ohm readings than Jt's by 15 at idle and 8-12 at 2000 rpm, but I would expect to see some movement at the gauge. Is it possible the gauge or the wire is bad for the sender? Anybody else with some data?

[summerinmaine]

So if the sender develops an open circuit (i.e. infinite resistance) then the gauge should peg to the max position and stay there, right?

 

This is what mine does.

 

Or should it return to zero psi with the ignition off?

 

The PO installed an aftermarket unit (Sun IIRC) that feeds oil to the gauge, but I'm wondering why he did that rather than simply fix the stock set-up. :dunno:

[jtdesigns]

So if the sender develops an open circuit (i.e. infinite resistance) then the gauge should peg to the max position and stay there, right?

 

This is what mine does.

 

Or should it return to zero psi with the ignition off?

 

The PO installed an aftermarket unit (Sun IIRC) that feeds oil to the gauge, but I'm wondering why he did that rather than simply fix the stock set-up. :dunno:

Cause he likes oil spills when that line gets pinched or fails... ;)

There is no way I'm going to pump oil,, or fuel for that matter into my cabin.. Forget about it!

[HOrnbrod]

Ohmed out the junkyard sensor from Jt. I tried to ohm out the new one, but I was doing so incorrectly. Instead of ohming to the block I was trying to do it passthrough. :headpop: In the process of trying to figure things out I switched back to the junkyard one.

 

Once I reread Eagle's post I ohmed out the junkyard one in the correct manner. Results:

 

Keyed on - 0-1 Ohm

Idle at 500- 700 RPM - 23-26 Ohms

1500 RPM - 42 Ohms

2000 RPM - 47 Ohms

2500 RRM - 50 Ohms

 

Hooked the gauge back up and had same results as before.

 

Never greater than 10 psi, some times less, some times more. I did notice a marginal amount of movement when I got the RPm climbing, but never more than 5 psi difference.

 

Its definitely putting out lower Ohm readings than Jt's by 15 at idle and 8-12 at 2000 rpm, but I would expect to see some movement at the gauge. Is it possible the gauge or the wire is bad for the sender? Anybody else with some data?

 

Here are the calibration values for the gauge:

 

0 PSI: 1 ohm

40PSI: 46 ohms

80 PSI: 87 ohms

 

I calibrate them with a decade box, which simulates the resistance of the sender. Your sender resistance readings are not too far off, so I think the problem might be the gauge itself, most likely a sticky meter movement, even though you got full scale deflection when you disconnected it from the sender.

[UNL1MTD]

Here are the calibration values for the gauge:

 

0 PSI: 1 ohm

40PSI: 46 ohms

80 PSI: 87 ohms

 

I calibrate them with a decade box, which simulates the resistance of the sender. Your sender resistance readings are not too far off, so I think the problem might be the gauge itself, most likely a sticky meter movement, even though you got full scale deflection when you disconnected it from the sender.

 

Is there a way to 'fix' the gauge?

[HOrnbrod]

Not really. Meter movement is governed by current flow thru the coils, which creates a magnetic field to deflect the gauge needle. No lubrication or anything like that. The best option is a replacement gauge.

[Eagle]

So if the sender develops an open circuit (i.e. infinite resistance) then the gauge should peg to the max position and stay there, right?

 

This is what mine does.

 

Or should it return to zero psi with the ignition off?

Zero ohms should put the gauge to zero psi. 88 ohms or more would peg the needle.

 

The PO installed an aftermarket unit (Sun IIRC) that feeds oil to the gauge, but I'm wondering why he did that rather than simply fix the stock set-up. :dunno:

Obviously, because he didn't know what was wrong or how to fix it, so an aftermarket gauge was the easiest way to know if he had oil pressure. I've bought used MJs with the same "solution."

[UNL1MTD]

Not really. Meter movement is governed by current flow thru the coils, which creates a magnetic field to deflect the gauge needle. No lubrication or anything like that. The best option is a replacement gauge.

 

well, I guess I am just going to button up the install and live with it for now. I feel good knowing that the sender is operating and that I'm getting respectable readings from it. Hopefully the gauge comes to life all of a sudden, but if not I'll swap it out in the future.

[jtdesigns]

Did you clean the 3 screws on the back of the gauge??