i'm kinda stuck here. i have been working on my 10AE trying to get the oil pressure gauge working correctly. before i replaced the blown engine, i noticed that when the engine ran weakly on one rotor, the oil pressure gauge would max out. so when i installed the new replacement engine, i installed a known good oil pressure sender. the gauge never worked with that sender in place. i went through a few differnet oil pressure senders and tonight, swapped in the old one. gauge maxed out. so again, i pulled a known good sender and swapped it in. the gauge no longer works. i noticed that there are different numbers on the oil pressure gauges. the one stating "8-C" is the one that makes the gauge max out. the other makes the gauge do nothing. i thought that the 81-92 oil pressure senders were identical. any thoughts on why this could be. here are the pics of the senders:

 

Mazdatrix shows the same sending unit for all models, 1981-1992.
You have a problem with the wiring or the gauge, sounds like.

 

but why would the gauge or wiring react differently to different senders?

 

Check the output impedance on each gauge while installed, while the car is running of course it needs to be disconnected from the little clip connector to do that.

The specs should be in FSM. If your "known good" senders are indeed good, that rules that out. Once you have done that, check the impedance between the clip connector and ground. I am not sure what the resistance on the gauge itself is supposed to be, and I am sure the FSM doesn't say it either, but you should have a good measurable impedance on that guage. If there is a short or broken wire, then of course the impedance will be really low or there will be no continuity.

 

make sure your capacitor is hooked up and bolted to the frame.

 

^^this is true. i know the other sender was good because it came off of agood engine. this is just not making much sense to me at this juncture. the FSM does not give a test procedure for teh gauge or wiring. it advises to use the "Mazda Checker" of which i do not have. it does give resistance values for the gauge though.

 

i believe it is bolted snugly to the top of the trans. i know it smooths out the pulses from the oil pressure sender to the gauge. i may have to remove and test and clean my current one or replace it with one off the shelf. perhaps thats something to do tomorrow after work.

 

It sounds like a problem with the clip or wiring that connects to the sender.

 

Driver side slave cylinder bolt if I remember correctly. Since there is no current actually moving through the capacitor, you can bolt it anywhere. As long as it is a good strong ground. You could use a self tapping screw to the firewall to mount it, and it wouldnt make any difference as it is just a resevoir capacitor.

 

the connector is clean and solid. the only difference is when i install the sender marked 8-C.

 

any other thoughts?

 

Well, the other thing to try is to replace the gauge itself. One of the senders may have messed it up. Not too much work.

 

i've considered that... just weird why one sender consistantly makes the gauge peak and the other doesnt even make it flicker..

 

What does this mean?
Was the "good engine" installed/running and the gauge was functioning correctly?

The first sender probably has a very worn or broken diaphragm and is simply shorting out internally, thus pegging the gauge.
The second unit might have a broken connector and the current simply has no place to go. Or, your wiring/gauge is faulty.

 

aftermarket gauge ftw

 

i will not go aftermarket. the car is a 10AE and i'm keeping it stock.

 

gauge was functioning properly on a running GSL-SE engine that i recently pulled.

i have tried other known good senders and all but the listed 8-C do absolutely nothing. this is why i'm puzzled.

 

Get your meter out. PUt it on ohms. One lead on the elect connection of the sender......the other lead to the body of the sender. Compare both senders. One is shorted to gnd internally.

You don't need a Mazda tester to check the gauge. Just look at the picture in the manual where you saw the test of the gaugge...........look and you'll see the ohms value of each reading. Go to the local radio shack and buy resistors of those values. Cost maybe five whole bucks for all of 'em. PUt one end of the resistor on the wire connector that attaches to the sender. Put the other end of the resistor to the block of the engine. Key ON.

Gauge needle rises and should meet the value for that resistor.

Grounding the senders connector to gnd for long periods will kill the gauge or at the least make it read plumb wrong.