Currently I'm using the old 2.8L OPSU on my 3100. I have replaced it once before with an aftermarket unit. I think it is failing again and I've heard of this style opsu being junk.

Anyways, Has anyone used a newer style unit with the factory gauge? I have one from my 3100 and it worked great with my '90 z24 gauges. Does anyone know how to wire in this sensor. It is also much smaller and looks more engineered then the fiero unit.

-Joseph

Get a better quality opsu?

I dont know what "style" you have, but I have been using the same opsu since I have had my Fiero, and it has never failed.

Standard motor products (in the red box) is a top of the line product including the offering of sensors and sending units. Look for a parts store that sell the branded (red box) product. Standard has a number of sub lines GP / Borg Warner etc that may or may not have the top of the line product in the box. (content aka quality of box is determined by the distributor) and in most cases the discounters like vance & riley have the house product. Look for the RED BOX. check out www.smpcorp.com for catalog info. reference engine management / standard. you can use the catalog to find the info and part number you need.

update it to the 88 2.8's OPSU. you will hafta search for the schematics for the conversion. i did it to my motor swap. that crappy HUGE old school one broke way too soon so i changed it out with the newer one. here is a hint to find the schematics, look under my name. good luck!

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1987 Fiero GT built by my brother, merlot566jka, 3500 LX9 from 06 Malibu, WOT-TECH.com 1280 grind stage 3 cam, LS6 valve springs, 1227730 ECM conversion, Darrel Morse solid aluminum cradle mounts, Truleo headers modified to fit the 3500, 36# inectors, 70mm 4.3 throttle body adapted to 3500 intake, ported heads, upper and lower intakes, lightly polished, tcemotorsports.com crank trigger wheel, CenterForce dual friction clutch, Flowtech Afterburner muffler, 2.5" piping, cat deleted, EGR deleted, SinisterPerformance tuning, C6 Corvette exhaust tips. projected to be 35 MPG with a guesstimate of 250 hp at the motor

The 3100 sending unit works fine as long as its the one for the gauge... Just make sure its the gauge sending unit version, not the switch. I think the "long" case is the sending unit, and the "short" case is just a switch for an oil pressure light.
I know that if you buy the 1988 Fiero 2.5L oil pressure sending unit, its the right one for the newer GM stuff. Much better than the old 2.8 sender..

Just follow the pinout for the car it came from. You should be able to find a connector on almost any GM car built after 1988. Look for one with 3 wires; some of them only had 1 as they didn't use it for a fuel pump switch, just the gauge.
IIRC, the tan wire goes to the gauge, the orange wire goes to always-hot ECM/Fuel pump feed, and the grey wire goes to the fuel pump positive side. I may have the tan and grey mixed up.

[This message has been edited by Steven Snyder (edited 09-29-2008).]

the 88 and up style like i used are both the same for the guage or the light. the first one was just for the light, then i went out and got one for my 98 blazer since that has a guage on it. its been working so far. no changes needed to be made.

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1987 Fiero GT built by my brother, merlot566jka, 3500 LX9 from 06 Malibu, WOT-TECH.com 1280 grind stage 3 cam, LS6 valve springs, 1227730 ECM conversion, Darrel Morse solid aluminum cradle mounts, Truleo headers modified to fit the 3500, 36# inectors, 70mm 4.3 throttle body adapted to 3500 intake, ported heads, upper and lower intakes, lightly polished, tcemotorsports.com crank trigger wheel, CenterForce dual friction clutch, Flowtech Afterburner muffler, 2.5" piping, cat deleted, EGR deleted, SinisterPerformance tuning, C6 Corvette exhaust tips. projected to be 35 MPG with a guesstimate of 250 hp at the motor

I heard dan used one off a old van of some kind, try a like 91 transport van.

Just make sure it's a 90 ohm and not a 120 ohm. They started using those on many engines in 89-90.

quote Originally posted by TK: Just make sure it's a 90 ohm and not a 120 ohm. They started using those on many engines in 89-90.

We always try to order the 90 ohm oil pressure sensor but we've had more problems with parts suppliers supplying the 120 ohm unit as that is the most common sensor resustance used on 80's and 90's GM cars. The sensor looks just like the 88 oil presure sensor but the 120 ohm sensor will pin the gauge.
Here's the fix. Buy a 1/4 or 1/2 watt 350-400 ohm resisitor ( cost is pennies) . Connect one end to the tan wire (pin e) of the C203 connector ( behind the console) and the other to the ground wire that is there ( there are two black ground wires there).
This will lower the max resisistance to 85-90 ohms at full pressure and the gauge won't be pinned. We just did this on my 87 and it works well.
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87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 10-01-2008).]

How do you check the ohms on these sending units? I work at a parts store, so I can check into some different part numbers and see what works.

quote Originally posted by Fiero_Adam: How do you check the ohms on these sending units? I work at a parts store, so I can check into some different part numbers and see what works.

Only way is with an ohmeter and compressed air. Clamp hose to the sensor end that fits into the engine. Apply 80 PSI of air pressure. Now measure the resistance from the center pin to the metal end on the sensor. Should read 90 ohms if it is the correct sensor; 120 if its the wrong one. Right now I have the 120 ohm sensor and with the 350 ohm resistor in parallel with the output my oil pressure gauge reads correctly. MOST of the sensors that I've tested that are boxed and sold for the 88 Fiero application have been 120 ohm units. This has led to speculation that a good number of these sensor are bad. No so they are just seling a sensor with the same shape and screw theads as universal and the 120 ohm version is not universal. .

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87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

Thanks for all the help guys. That is exactly what I was looking for Hudini. I have the long opsu already that worked my z24 gauge correctly. Hopefully it is not the 120ohm unit. Right now my oil guage dances around during cruise or idle. I'm pretty sure it is bad.

-Joseph

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1987 Fiero SE/Fastback - 3100HO (Ported LIM, Ported Heads, Competion Valve Job, LS6 Springs, 3500 UIM, LX5 65mm TB) / 4t60e full manual / ZZP shift kit / 7730 ecm Emulated w/Ostrich - Soon to be bottle fed!