Oil Pressure Sender Wiring Color?

[sidepipe87]

The oil pressure gauge in my 2.5 MJ is always maxed out no matter what. Did some research on here and found the Renix will default to maxed out when it fails, so I bought a new oil pressure sender and went to install it. The previous owner apparently just disconnected the sender and screwed an oil line in its place at the block which connects to an aftermarket Autometer oil pressure gauge which is just kind of hanging out in the console... I don't care for this and want it back to stock however I cannot find which wire was supposed to connect to the sender. Anyone know which color wire I should be looking for in the engine bay? 

Also, I bought a sender for a gauge not idiot light since my cluster has gauges. Well when I pulled the cluster the other day I saw it had a Chrysler pentastar on it (truck is an 86) so it must've been replaced. Will the wiring be different if the truck came with idiot lights and not a gauge? 

 

What I really need to do is buy a factory service manual but I've found a few and don't know which one is the correct one I need or if there are multiple. I've seen M.R. 277 and M.R. 278 body manual and not sure what the difference between them is. 

[onlyinajeep726]

The gauge cluster is electronically compatible from '84 - '90, so the PO likely used one from an '89-'90 or thereabout. 

[jimoshel]

The 277 is the FSM. It covers all the mechanics, engine, wiring, tran, axles, etc,. etc. The The 278 covers the body and related parts. The original 277 is harder to find altho still one occasionally on ebay and Amazon. There is a CD of the 277 available and quite common on ebay. I think the going price is $19.95 if I remember right.  The wire you're looking for is light blue. The wiring is the same for guage/lights.