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Author Topic: Will Mazda Miata Oil Pressure Sender Work?  (Read 12032 times)

capriBill

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Will Mazda Miata Oil Pressure Sender Work?
« on: October 06, 2013, 05:57:14 PM »

My Oil Pressure Sender does not look to be working correctly. Sometimes it drops near the red for no reason and later gets good again. I looked at it and it looks like it is leaking too.
I was looking for a replacement. They are not sold anymore and the old ones available are too expensive. I did find a Miata version. Have any of you tried that? It is at this web site: http://www.partsgeek.com/gbproducts/DC/8532-05268552.html?utm_source=google&utm_medium=ff&utm_content=DN&utm_campaign=PartsGeek+Google+Base&utm_term=1990-1994+Mazda+Miata+Oil+Pressure+Sender+With+Gauge+Standard+Motor+Products+PS-261+90-94+Mazda+Oil+Pressure+Sender+With+Gauge+1992+1993&fp=pp&gbm=a&gclid=CPq03siZg7oCFdFDMgodHy8Adg

Also, how hard is it to get the old one out to replace it? I was under the car cleaning the connector to it. It took a while to get it off, clean it and put it back on. I am worried if replacing the sensor will require removing other pieces. Have any of you done this?

Thanks,

Bill, 92 XR2
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Rocketman

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #1 on: October 07, 2013, 02:04:49 AM »

Welcome to TeamCapri!

The old sensor comes out real easy, it's just a pipe thread. You may need an adjustable wrench.

Those are expensive senders, maybe try a junkyard unit first?

I will say, out of all the Capri's I've owned not a single stock oil pressure gauge has ever worked correctly. My newest XR2's gauge works sometimes but other times just sits at zero. And that's the best I've had so far. The accuracy when it is working (like that of the boost gauge) is questionable as well. I haven't really looked into it, and even so the sender may be fine and it could be a bad connection on the start/charge harness (the OPSU wiring is separate from most of the other sensors) could be an issue with the gauge itself too.

Personally I feel investing in an accurate aftermarket gauge would be the best option. For the price of that sender you could purchase a nice electronic gauge with its own sender. There are much cheaper mechanical gauges too but some folks don't like an oil line running through the firewall.

My 2 anyway :)
« Last Edit: October 07, 2013, 02:06:52 AM by Rocketman »
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blueamber

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #2 on: October 07, 2013, 02:44:58 PM »

I don't know the answer to your question.  You need to find out the thread area length of the sensor, the thread spacing and diameter numbers, and the output of the sensor based on pressure it sees.  Finding an equivalent new part would be a good project for someone to benefit all of us with senders we can't rely on.  I personally would love to stop the car and have it towed in with a very low pressure indication, rather than guessing that this low pressure reading was just like the last time, and I could ignore it...Chris
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Rocketman

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #3 on: October 07, 2013, 07:13:12 PM »

But how do we know it's the sender that is the culprit of the poor gauge situation? Has anyone sat with a multimeter directly on the sender's terminal to see if the signal drops out when the gauge does?

The 1.6 Miata uses the same block (89 thru 93 IIRC) and should use the same pressure sender threading, providing it taps it in the same location.

Now, is it electrically compatible with the Capri? That'd be my biggest concern

« Last Edit: October 07, 2013, 07:17:38 PM by Rocketman »
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blueamber

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #4 on: October 07, 2013, 10:03:56 PM »

A Mazda 323 sensors would probably work, but you would still be looking at finding used parts off a 20 year old car.

The sensor is a one wire unit, looks like a variable resistance.  That wire goes directly to the dash cluster, straight to the meter.  If it screws into the hole, and is a one-wire sensor, it would work, with the only question being if the gauge accurately reflects true low and true high oil pressure.  Its just a resistor, no harm could come with trying other sensors.

I don't have the specs on what our meter measures under various pressures, but this might be dug up somewhere, and compared to other sensor types.  If I find it, I'll share the info.

You said it yourself, these sensors are all over the place on accuracy.  I know that heat kills electronic components eventually, and a part screwed into the block of an engine stands a good chance of failing eventually, or at least going intermittent...Chris
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Greg_B

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #5 on: October 08, 2013, 01:43:36 PM »

In a previous job I worked for a comapany who built pressure sensors and gages for heavy truck, off-road equipment, Mercury Marine, OMC etc.

I did some checking after I got my 93 N/A 5 years ago, so this is all from memory.  The single wire sensor varies resistance based on oil pressure.  There is a resistance table in the FSM, for checking gage, at various pressure readings, or needle position on gage face.  Find that table, use an ohmeter from sender terminal to ground.  If it is close to table readings sender is OK.  Dirty internal contacts can cause changed resistance.  I have a decade box that I have used to simulate a good sensor to double check my gage.

I did find a replacement sender with a resistance curve close to what the gage needs to see.  But the thread in the block is a Japanese? pipe thread 1/8-28, not the us standard 1/8-27.  Never did finish looking for the adaptor.

I think the miata part is either just a switch, or a fixed resistor so the needle stays in one spot, unless it is from an early miata, somewherethey changed to a dumb sender.
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blueamber

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #6 on: October 08, 2013, 05:03:53 PM »

OK, I found a Miata thread where a guy put a aussie capri oil sender into his early 90s miata, worked great, he got it at a junk yard.

If that is true, then the Miata substitute you found would probably work, it's a Standard Motor Products PS-261 sensor.  These are on ebay, cheapest today is $50 from a questionable seller, or $89 from a better seller, free shipping.

Ebay ads claim the sensor works for 90 to 94 Miata, 93 to 95 Ford Probe..Chris
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Rocketman

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #7 on: October 08, 2013, 10:59:47 PM »

4cylinder or V6 probe? I have a '95 probe GT engine at my shop I can check.

The 323/escort/protege 1.6 & 1.8 sending units are all just switches for a low pressure light. Won't work with our gauge. They're significantly cheaper though, if you wanted to wire in a light
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blueamber

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #8 on: October 09, 2013, 12:02:50 PM »

Spec sheet says 95 Probe V6 uses that Standard Motors products also.  That company looks big into Miata parts sourcing.

I just gotta believe our big old clunky sensors are mechanical relics inside, just waiting to go nuts all kinds of ways due to temperature and old age.  With only one wire attached, it is probably just a big old volume control type rheostat attached to a mechanical arm that pushed the rheostat back and forth.  Newer units are 100% electronic, with voltage supplied to the sensor, which is probably something called a strain gauge that senses pressure with no moving parts.

Looking through ebay, I didn't realize that an adapter was available, probably for our cars, that fits between the oil filter and the engine.  It has 2 holes in it that could be used to fit your own oil pressure sensor and oil temperature sensor.

I also think adding idiot lights would be a good thing.  I used to be more attentive to instrument readings, but not so much anymore (not even the speedometer so much), so a warning light/siren/whoopee_cushion_vibrator letting me know the coolant temperature is in the red, or oil pressure is gone, would be helpful...Chris
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capriBill

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #9 on: October 11, 2013, 09:03:46 PM »

The reason I think it is the sensor is that all of the gauges have been good except the temperature (often) and oil pressure (seldom). I have had to replace the temperature sensor 2 times during the life of the car. I only have 76,000 miles on the car. The last temperature sensor I found has been working great, no longer shows a too high reading, and only cost $3.53. I found it here, and purchased an extra one for the future: http://www.rockauto.com/catalog/raframecatalog.php?carcode=1196658&parttype=4748

I am looking for a new sensor with a warranty that we can all use for the oil pressure. I do not want to buy an old Capri one at an outrageous price. I did see that same Miata thread about using a Capri sensor in a Miata and it worked great. That is why I hope the reverse is true.

My gauge shows a good reading 99% of the time, it is only sometimes that it all of a sudden drops. After a while it goes back to good. I do see oil on the sensor indicating to me that it starting to leak. I do think that the reading is lower than it used to be, but cannot be sure.

Have any of you replaced the sensor from under the car while the engine is still in the car? I do see what looks like an engine mount that makes access to the sensor difficult. Did you remove the mount to do the work?

Thanks,

Bill 92 XR2
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Rocketman

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #10 on: October 11, 2013, 10:45:45 PM »

I will check the 2.5L V6 OPSU and get back with the results
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Rocketman

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #11 on: February 20, 2014, 06:41:24 PM »

I will check the 2.5L V6 OPSU and get back with the results
Car has been buried under snow all winter. I'll Check when it warms up a bit.
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capriBill

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #12 on: April 20, 2014, 10:19:15 PM »

Hi Rocketman,

Are you going to be able to try this soon? My oil pressure is good 70% of the time, then drops almost to the red part of the gauge and stays there for a while. That is why I think it is the sending unit. Do you think the Oil Pump will only work 70% of the time? I assume either it works or does not work. I did try cleaning the connection to the sending unit, but that did not solve the problem.

If you are not going to be able to try it, I will just buy the part and replace the sending unit and will hope it works. I again ask, do other parts need to be removed to get it out with the engine still in the car?

Thanks,

Bill
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Rocketman

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #13 on: April 20, 2014, 11:42:42 PM »

I've put in ZERO wrench time on the V6. Weather hasn't been great and the nice days I have had, have been spent casting in the foundry. I'll try to get to it soon.

Correct, if the oil pump wasn't working, your engine would seize in a matter of mere seconds.

You may have to remove the oil filter to get easier access to the OPSU. Maybe the intake manifold brace. You might be able to get at it without removing anything, with the right socket/wrench
« Last Edit: April 20, 2014, 11:44:33 PM by Rocketman »
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capriBill

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Re: Will Mazda Miata Oil Pressure Sender Work?
« Reply #14 on: June 06, 2014, 12:48:04 AM »

Hi Rocketman, the price of the part is going up.  :'(

Do you think you can try the one you have soon? I am thinking of just buying one and trying it myself, but just hate to waste over $100, time, and most likely skin, if it does not work.

Are you going to the Mid-America Capri Gathering in Freeport Illinois? I'd like to see your car. Mine is a perfect, except for this sensor, 92 XR2 with less than 80K miles. It is 98% stock.
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