Is there a difference between the two?

I have an '89 Iroc-Z with the L98. The oil pressure gauge has stopped working. As a matter of fact, the needle is pointing 180* off of where it should normally be. It does nothing when I start the car or shut it down. Disconnecting the battery did nothing. I assumed it was the oil pressure switch just above the oil filter. I ordered an AC Delco unit and replaced the part...nothing changed! I've been researching on past threads and found that there is a sending unit attached to a brass 90* fitting but it was on TBI cars. Do the TPI cars have them as well? I've also read that there are known issues with the rally gauges on these vehicles.

Any help is appreciated, thanks.

 

TBI cars just have it in a different location. You won't have one by the oil filter and one behind the manifold.

 

My 88’ L98 has the one by the filter and one by the distributor. The one that worked the gauge was the bell shaped one near distributor, after replacing it my gauge worked much better, not perfect but a big improvement. Also this is one of those things that seemed to change during different model years...I believe 89’ only had the sensor near the filter. Might want to check wiring to see what’s going on.