My oil sending unit is going nuts. I thought it went bad after just changing it less than a year ago. Replaced it under warranty and it's still tacking out. It runs a tad high under idle, then when you accelerate, once the pressure gets to 60, it just tacks out all the way. When I unhooked it and fired it up, it did the same thing. Could just the plug be going bad and grounding out under load? I hate electrical gremlins....

Just realized I haven't checked my FSM but would like some possible pointers before I dive into the book tonight.

 

The problem is in the wire to the sender and its splice in the harness. This gets corroded and loose and the connection suddenly gets poor and the signal of varying resistance is junk and goofy.

Unless you can access the harness and repair/replace this section of harness,. you'll have to clean what you can and simply wiggle the harness around until you get decent OP signals and TRY to tie strap the wires in place so it'll stay for a while. 80 psi is the default for disconnected or no signal, and showing 20 or 60 when key on but not running shows poor contact somewhere. High press at idle then lowering with rpm same thing...bad connection in the wire probably at the splice or the plug.

 

I replace mine because it was leaking. New one from the Zone gives crazy readings. Like to stick on 26 or some other number at times.

 

Yeah, I went with A/C delco for both my replacements. The one before that was a zone and never worked right. Thanks leesvet, I'll check it out this weekend. That's about what I figured...

 

I thought I had great pressure at idle until I realized that I also had 30 psi with the key in my pocket ! Hmmmm 30 psi no key and 23 psi when idling. uhhhhh

The sender works by sending varying levels of resistance to the cluster that interprits the signal and gives us a number to look at. The more the resistance in the circuit the more the pressure ( i think it is) so no signal or an open circuit is full press of 80 psi. The easier it is the less it shows...
Using the engine off and knowing there should be ZERO pressure, thats what I used as a baseline to find out when I had good contact. It really came down to jerking the harness around and securing parts of it to get it stable. Since the area where the splices is not accessable with the engine installed, thats all you can do until the motor comes out. The harness is just below block height where you cannot work on it...
Thats when I discovered that there are about 6 splices in that area that come from GM with black tape and not much else. This includes the important set of grounds that everyone talks about on the bellhousing or block near the oil filter.
They rot, get loose and the inj start acting up,. all the sensors on the left bank act up and give false data to the ECM and it goes to hell from there...

 

Oh lovely, sounds like something my car would do to me.... Thanks again.