Oil and Temp sensor wiring ??'s

[aggie91]

Here is my issue that I need some help on.

I am putting a 1990 Suburban cluster in my 1985 truck while doing the LS swap. I have most of the wiring figured out, but have a couple of questions I need to get clarified.

I bought the sensors/senders for the oil pressure and water temperature for a 1990 suburban. First Question: Did I really need to do that? Or would the senders from the 1985 work with the gauges in the 1990 cluster? I ask that because the 1990 sensors are multi wire plugs on both where as the 1985 ones are single wire for the gauges (the oil pressure does have multip[le wires for the ECM in the 1985, but all that is going away...)

Second Question: If I do need the 1990 sensors, do I just run the single wire for the correct pin on the connector for the sensor? The wire schematic shows (for a 1990 suburban) shows a single tan wire to the center terminal and the connector I pulled from the wrecking yard has a tan wire on the center terminal, the other two wires being orange and gray.

Third Question: The 1990 temp sensor has 2 wires, the generic connector that came with the new sensor has both wires being black. The schematic show the harnes wire as a dark green. Which pin on the connector do I use? What is the other wire for?

Thanks in advance for any help...

[aggie91]

I did some more research last night. I figiured out the Oil Pressure sender. I will be using the 1990 sender. I only need to run the tan wire to the center pin. The other 2 are for the fuel pump circuit which I am not going to use.

now I just need to figure out the temp sensor wiring...

[88Ironduke]

Just a thought from the outside view on your fuel pump circuit. The fuel pump relays in late model GMs were primarily operated by the ECM/PCM. The engineers also added a circuit to operate the fuel pump relay ECM via the oil pressure sending unit in the event of a internal driver failure onboard the ECM/PCM. Misconception that it is a safety device that cuts off at low oil pressure so you don't grenade an engine. Its nothing more than a back up circuit to ensure the fuel pump relay always works.

88Ironduke

[aggie91]

Thanks for the input 88Ironduke.

I figured out the temp sensor wiring issue that I was thinking thru. After further investigation of the 1990 vehicle wiring diagrams (found on this site BTW), I did some parts searching. Turns out that GM put temp sensors/senders in the engine for a few years. The one that I first purchased was the one wired with a yellow and black wire in a 2 pole connector. Those wires go to the ECM on the 1990 engine. There is another temp sensor for the gauges, it is hooked up with a single dark green wire.

So a bit of searching on Rock Auto, turns up the part number for the sensor I need, TU66. So off to Auto Zone I go last night to return the one I do not need and get this one. they had it in stock and it was $3 less than the one I returned..

So, looks like I have all the items I need to complete my LS swap with the 1990 instrument cluster in my 1985 GMC C15.