Alright guys, I stayed off this for a couple of years, but now need your help/advice to finish up.

I have a 4 port 13B in a 1981 RX-7. The original factory wiring harnass is being used, just no longer with a 12A engine. I did not have an oil pressure sending unit or its port in my 13B.

I have very recently purchased the oil pressure sending unit from Mazdatrix and have installed it into a new plate between the oil filter and the pedestal. That's all done.

On the electrical end, I found a connector part that fits the side terminal clip on the sending unit. The connector was soldered and heat shrunk to an unused harnass wire and connected to the sending unit. NOTHING ! That harnass wire (single wire) that is being used is the only one that is in that vicinity and that also makes the stock oil pressure gauge in my cluster react by maxing out when grounded.

Anybody out there know what I'm doing wrong ?

 

the stock sender might not work with an aftermarket guage. i know that the temp sender on an '83 engine wouldn't read right in my 808. had to use a per 80 sender due to the difference in resistance of the sender for the guage in the 808. this could be the same issue with the oil pressure sender. may need a sender with resistance that matches the guage.

 

He's using a stock gauge... The sender units are all the same from 80-85 and then some way past that point in years..


I'd have to say if it maxes out when it's grounded that there is no oil reaching the sending unit at it's present location...?

 

Is it in a block between the pedestal and the rear iron or actualy as you posted? The sender needs to be able to go to ground. If there are o-rings stopping it from going to ground it will not work.

-billy

 

Did you use anything on the threads for the sender like teflon tape if so you will not hve a ground. remove the teflon tape and reinstall it is tapered to seal. if all else fails look in the wire diag. for the wire cooler to gauge. Good luck.

 

actually it should still ground thru the stud and nut holding it together.

 

That is why I was wondering if it was a oil block or some type of sandwich adapter. He said it was under the filter above the pedestal. Just tossing out ideas. Could be a resistance thing. I would take a wire and touch the back of the sender to ground just to eliminate the possibility.

-billy

 

The new Mazda sender is screwed into an adapter that is directly in between the oil filter and where the oil filter used to sit. The gauge is stock and in my OE cluster. The adapter is billet aluminum.

When we hold a wire from the outside of the sender to chassis ground, the meter reacts by maxing out and staying there (up).

Still scratching my a$$...

 

Where did you ground to. The big diameter part or the smaller diameter part where it screws into the block? "A" or "B".

I have never tested it but I would assume the A body and B body are insulated from each other. I would asume the B body would need to go to ground and the resistance across the circuit is what moves the needle.

If grounding B with a wire makes the needle peg then not sure what the problem is.

So the adaptor is a sandwich plate. Did it screw to the base with a new center post for the filter?

-billy

 

Exactly. New center post holds the piece in place. The oil filter threads onto the top of the new post.

 

i re-read the original post so i understand this plate is between the filter pedestal and filter so no the sender will not ground. what year is the 13b ur using? it should have a threaded hole for the sender, it might have an allen head plug in it. it's on the rear housing right under the oil filter pedestal, and next to where the coolant sender threads into.

 

Run a ground wire from the adapter plate to the engine. Keep it away from the sender.

 

Here's the setup. I'll try grounding the back of the anodized ring to the engine when I have time to properly tap and get a suitable length of wire.

 

The sensor wire is the ground. The tab to connect the wire to the sensor is isolated from the body, then the body itself completes the circuit.

 

usually when your sensor goes bad so does the gauge. My old car the gauge would max out on ground, but nomatter how many sensors I tried it didn't work. I thought I had a bad sensor, but when I put my engine in the new FB it works. SO your cluster just might be bed.