3100 Oil Pressure Sending Unit removal

[BurleyPiper]

I have searched the boards and found many answers about where the sending unit is etc, but have not found out the most important part of the equation. Can anyone tell me if I need a special socket to remove it, and do I need to drop the starter to do so? I am ready to put in my new aftermarket gauge and this is the only step left, installing the new sending unit.

I do not need the T-fitting as this unit will hook up to the stock idiot light as well as the new gauge.

I have a 97 GT, auto, 3100.

Any help would be appreciated.

[sunrunner_pei]

I've never heard of a sending usint that will also function as a switch for the idiot light, but OK. :)

There are special sockets you can use. however they are unnecessary if you're willing to be inventive. Kelly & I used a sink wrench on ours, and it worked perfectly. No need to remove the starter, but you may want to disconnect the battery first just in case you cross the terminals on the starter.

The wrench we used:
http://www.gaownersclub.com/images/misc/sink_wrench.jpg

[BurleyPiper]

Thanks Shawn, I have one of those so I will try that. The new sending unit has 1 lead on it that goes to the new gauge, and one that goes to the stock wire from the old gauge.

[sunrunner_pei]

Oh, you have an actual gauge in your stock cluster? That's the difference then. The 1999-2005 only have an idiot light, not a gauge. :)

[silvergtjrad]

You can just use a pair of channel locks on it if it doesnt need to be saved. I have the special socket for it, and used it when i took mine out. It wasnt screwed in extremely tight so you shouldnt have much of a problem

[rixGAphx]

BTW, oil sending units (whether idiot light or gage) have tapered Iron Pipe Threads, just like coolant temperature sending units.
IPT are the same as used on galvanized iron house water piping.
They get tighter EXTREMELY QUICKLY as you screw them in.

You should NOT try to tighten these much more than finger-tight, assuming the fingers are Arnold Schwartzenegger's.
Seriously, as others have found out the hard and expensive way, over-tightening an ECT sensor with IPT's will CRACK the aluminum intake manifold.

And even though the oil pressure sending unit screws inot the iron block, cast iron is also pretty fragile in tension.
The 'sealing' that occurs is between the sender's flat face, the resilient washer, and the milled face of the block.
* * *
Your '97 3.1 has an OP GAGE???

Doesn't show as such on the wiring diagrams in my Chilton's, but then Chilton's is frequently wrong in this regard.

Anyhow, Chilton's shows ONLY an idiot light switch, and this is NOT compatible with an aftermarket gage.

Oil pressure sending units for GAGES work completely differently than those for Idiot Lights, on nearly every conventional car, computerized like the GA or not.

And with the GA's computer, the Idiot Light Sender tells the 'puter (not the dashboard bulb) when the pressure is low.
The fuel pump is shut-off when the computer thinks the oil pressure is low for more than a couple seconds.

So you may be in for a rude awakening if you don't have an actual gage, and you don't use the Tee fitting to maintain its function vis-a-vis the computer.

Finally, Idiot Light Senders (OP and EC) only have one wire, and they ground-out to the block (Gages *usually* have a supply wire and return wire, and don't need to ground-out).
So whenever you install an Idiot Light Sender, you MUST 'maintain ground' between the metal threads of the sender and the metal threads of the block (and Tee fitting, if used).
This means no grease, oil, anti-sieze, teflon tape, or plumber's pipe dope on the threads, since all these are electrical insulators and they prevent good grounding.
Clean adn dry the block threads, and allow both metals (iron and brass, or whatever) to fully-touch.

Hope this helps,
-Rick