zero13

OK, After reading multiple OPSU threads, I thought I was ready to tackle this project. But info here didnt apply to my situation, so I'm going to attempt a little tutorial for others in my shoes...
1. Reason for this attempt: hard starts,which has been only recently...only to tackle the easy fixes first.
2.Purchased the OPSU(oil pressure sending unit) socket for my 91z28 which is supposed to be 1 1/16(Lisle,from Amazon), and the SMP(standard motor products OPSU),PS228.
3.Located right above oil filter,this job seems fairly easy...but wait....
4. OPSU on car had a large diameter silver housing on it(see pix for reference), not allowing me to slip socket over to get to removal.
5. After some counseling from mechanic friend, told me to bang/bend of the housing,as it is most likely just fluted to fit the nut at the base.
6. Carefully I bent it off,away from the base nut(near block)See pix.
7. The socket I bought was not the right size for the job.This style needed to be 1 3/16.See pix.
8. After breaking OEM one away from base, able to use the 1 3/16 socket to remove the original(i believe to be the original)
9. Installing new,proper OPSU is a breeze after all this
10. Mechanic asked if there was oil in connector when I removed it, there wasnt, and he said thats good.
11. Refer to the pix, hope they help someone recognize the issue when they come across this...



original OPSU tpi 5.0 91 z28.....Pic#1





after breaking apart from flange/nut..using vice grip/hammer





1 3/16 size socket needed to remove base nut at block.

zero13

Once I actually receive new unit, and install it, I will follow up with any special circumstances/info...Will also let you know if it helped with any starting issues...Some people may say this wasnt needed, but awhile back I saw my oil gauge needle act erratically,although I only noticed this ONE time in recent memory, so either way, it was only 30 bux to do..If that was an original 24 year old OPSU, then I wont feel to bad replacing it...but it does LOOK sturdier than the new type they are selling....

zero13

OK, I have a bit more info for you guys attempting to do this job. My 91 TPI definitely had the original OPSU from 1991 on there. The size socket needed to remove the ORIGINAL one would be 1 3/16. Sunnex makes one for about 27 bux from Amazon. The new ones people are buying will need the 1 1/16 OPSU socket, which will fit over the unit once you disconnect the electrical connector. Plenty of room to get socket on, and a ratchet(I have headers, and they arent in the way at all).
I dabbed the end of the new OPSU with black RTV silicone,even though it comes with some sort of thread locker already in the threads. I tightened with the new socket I purchased(1 1/16) and made sure all the threads were buried into port(didnt want to overtighten, but also dont want any leaks/tested, and inspected for leaks.)
Last, but not least, I took a pic of my idling(in park) gauges, it doesnt show you guys anything in particular,just that its reading a pressure and holding well.....My only concern was after shutting engine off, gauge needle stayed at 30psi. It didnt go to ZERO until I went to start car and put key into the run position. Chime in to let me know this is standard operations or not.As I dont recall, and will only be back to car in about a month to start and run some gas(in storage for winter)

Thanks, check out the pix for reference. Hope it helps one soul out there...

new OPSU,model #...and notice the thread sealer already on unit.




new unit installed, using 1 1/16 OPSU socket, also dabbed black rtv on threads as well.




gauges at idle,in park..nothing to see except the fact that new gauge is reading/operating...recently removed gauge lense to clean as well.