Low-Oil-Pressure Light On

8/21/2019 – “The first step would be to verify the engines oil pressure with a mechanical gauge connected to a pressure port on the engine. Usually by removing the lights electrical sensor. Replace the switch with a gauge, crank it over with the fuel shut off and see if the gauge registers any pressure, if good your good, replace the switch and go. If no pressure you have a major problem.”

“Most oil pressure switches complete the ground circuit to light up the bulb. Disconnect the wire from the sender and turn the switch on, if the oil light is still on there is a short to ground somewhere in the wire (ground) going to the bulb. If the light is off, I’d suspect the sender may be bad, it could be gunked up to where it won’t open, or have a rip in the diaphragm. Pay attention to the threads if using an adapter for a test gauge, some Japanese automakers used BSP threads for senders for a long time, not sure if it extends to tractors but a mismatch could cause an irritating seep.”

“A clogged oil filter can cause low pressure and is cheap to change.”

“Since the light comes on at low engine speeds and then shuts off, the oil pump is probably fine; if the pump were dying, you’d see low pressure at high engine speeds as well. The most likely culprit is the sensor that operates the light. The sensor is screwed into the engine and has a probe that resides in an oil passage. It’s basically an on/off switch that uses the oil pressure to close an electrical circuit. Sometimes a particle of dirt or some other foreign matter gets into the probe and fouls the part. The sensor is fairly easy to replace—as long as you can get at it, which is ­sometimes difficult. Unhook the wiring, loosen with a wrench, and follow the instructions to replace the sensor.” From here.

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