My 91 RS has the oil pressure switch/sender combo above the oil filter. I do not have the sender by the distributer. I installed an after market oil pressure gauge today, but I couldnt get the little square headed plug GM put in the block next to the dis out.
I had already gone threw all the hell of modding my dash and running the tube for the gauge so I wasnt about to say screw it at this point.
what I ended up doing was removing the stock sender/switch above the oil filter and connected my mechanical gauge fittings there.
I started the car and it is running fine, and my oil pressure went right up to 35psi and sat there wile idleing in my drive way. only negative effect I noticed is that the stock gauge stays pegged past 60psi. which it not working I knew would happen.
I have a couple of questions thoe.

1. the tube that goes to the gauge never completly filled up with oil. there is still some air in it. is that normal?

2.was it ok to remove the factory sender/switch combo? I havent any idea what else it does aside from send the oil pressure signal to the gauge, but Im sure switch is in the name of it for a reason.

I still havent driven the car yet, so if this was a bad thing to do please let me know so I can put the stock oil pressure sender/switch back in b4 I trash my engine.

 

Everything should be cool , I did the same exact swap about 2 weeks ago , and everything has been fine. And my tube has never completely filled with oil either so I assume thats fine aswell.Hope that info reassures you. Good luck.

 

Thanx, that does make me feel better knowing some one else did the same thing and Im sure others here are bound to have done the same also.


Id still like to know what switch means. if any one knows, what exactly does it switch?

 

IROCaholic did you do any thing to seal the fittings that came with the mechanical gauge?
reason I ask is after I got home tonight and let the car sit for about 5min I moved it and noticed there was a little puddle of oil where it was parked, and my car does not leak oil so I know that is what it has to be from.

 

No I didnt seal it , and I notice the same thing the other day only my was like a drop of oil. I am going to end up doing that this weekend , I dont know what I am going use to seal it though.

 

I had the same problem taking that plug ot of the back of the block. I ended up doing it while the engine was out and used visegrips. I also have air in my tube. as far as the original swith on your car, I would try taking that plug out and re hooking up you factory gauge. Im not sure but I think that is connected to the fuel pump realy and if I senses low oil or no oil, it shuts the pump off so you dont damage the engine. Work at geting that plug out

 

Air in the tube is totally normal with a mechanical gague. The tube dead-heads against the back of the gague so the only way the air will purge out completely is if the line is leaking at the back of the gague (that would be bad).

If you have leak determine if it's leaking past the threads (easy fix) or if it's leaking past the compression fitting around the sender tube. 9 times out of 10 the compression fitting is tightened down either not enough or too much. If it's tightened down too much (very common) you have no choice but to unscrew it, clip the line to get to fresh hose, put in a fresh "crush bushing" and try again. It doesn't need to be "tight" and you definitely don't want to tighten until it bottoms. It's a very uncomfortable tightening process since you stop well before it feels like it's "tight". Hard to explain unless you've done a few. Try leaving it a little too loose and then tighten gradually until the leak stops and you'll get a feel for these quirky fittings pretty quick.