|Originally posted by Lou6t4gto:|
I came back with a 4 wire pigtail off a 3800. will this work for the 88 fiero sender ?
Yes it will work fine. The fourth wire doesn't connect to anything. You can pull it and replace it with a plug if you wish. Don't pull it and leave it open however since moisture will get in.
Looking at your 88 oil pressure sender - The Tan middle wire goes to the gauge. The two outside wires, Orange/Black and Tan/White connect to the fuel pump relay contacts and C203. It doesn't matter which pin goes to which contact. You can leave the wires off but if your fuel pump relay ever does fail, you would then be stranded. If you wire them up, and your fuel pump relay fails you will have longer crank start, but your Fiero will still run.
That said, many people with 3800s and the stock 88 Fiero have a problem where the oil pressure gauge is pegged at 80 PSI when the engine is running. The 3800 can produce over 80 psi of oil pressure. A remedy is to use the 4 pin oil pressure sender from a 98 Bonneville. The gauge on the Bonneville reads 0 - 40 - 120. The sender is still a 0 - 90 ohm sender. So by using the Bonneville sender, your stock Fiero gauge would read 0 - 40 - 120. You could do something to relabel your gauge, or you could just know that instead of 80, the full right position is actually 120.
When using the Bonneville 4 wire sender you will need that 4th pin (Black), the one that does not connect to anything on the Fiero sender, to be connected to ground.
On my harnesses I use the 4 wire connector with the 4th pin wired to ground. That way it will work with either the 88 Fiero 3 pin sender or the 98 4 pin Bonneville sender.
[This message has been edited by phonedawgz (edited 11-09-2013).]