An oil gauge question

[Michael Benardo]

So here is a picture of the fitting on the side of the engine. The small tubing coming off the top is the going to the gauge inside. I'm not sure what the switch/sensor with the three wire connector is for. Previously I thought it fed the oil light on the instrument cluster, but it has three wires, not two like I expected. I searched Rockauto and Amazon but neither shows a three wire unit, only one and two wire. Any ideas????

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Does your truck have the stock wiring harness, or one from a later year? The 78 and later uses a three-wire plug onto the electric oil pressure switch on 6 cylinder models, V8 trucks use just two wires, but the 77s are supposed to have a machanical gauge with that little tube, so this sender should not even be there. Light blue would go to the choke heater, the pink and the dark blue would to to a gang connector, so it is possible that your truck has a 78 wiring harness in it. Try disconnecting that plug and see it anything changes or does not operate, and trace those wires. They might just be taped and stored.

 

[tucker]

i have had that prob before,i had put new copper line in but did not clean the tips. new guy tucker

 

[CRM]

I checked the entire tube this afternoon for kinks or other issues but found none. I traced the wiring from the pressure switch along the firewall where they terminated at a terminal block. It was too cold outside to continue the search right now. Supposed to be warmer tomorrow.

 

[Turbo Dog]

First thing I would do is to get rid of the mechanical oil gauge. They scare me and took out an engine before. The line broke going about 65 mph and the engine locked up before the gauge showed a drop in pressure. It happens really quick.

Otherwise, if you want to keep it, you need to buy a test kit with a quality gauge. Plumb it into that Tee then place the gauge where you can see it while driving. Drive down the road at varying speeds and compare the readings on the two gauges.