Mercruiser 2000 4.3 carb oil pressure gauge ohms reading

[QBhoy]

Hi
A friend of mine has the engine above and the oil pressure gauge is not functioning.
I haven't looked into it much at all, apart from testing the voltage at the gauge. It reads 4 volts and the backlight doesn't even come on. 100% certain it isn't a genuine low oil pressure.
I will be trying to diagnose the fault tomorrow.
Does anyone have any idea what the resistance (ohms) reading should be at the sensor when cold, warm or anything in between, should it come to that ?
Thanks.

 

[Scott Danforth]

Sender is 240-33 ohm sender

Use mechanical gauge to test

 

[QBhoy]

Thanks Scott.
Bloody awkward bugger of a location on this particular boat. It's a Monterey 180 edge with a well boxed in engine.
Would the 4 volts indicated at the gauge suggest anything to you Scott ? Rest of the gauges are perfect, so surely not a common earth problem. I'll probably try bridging the power first, then go for the sensor, if not.
Thanks again Scott.

 

[Bt Doctur]

all the gauges should be at 12v or battery voltage, start there

 

[QBhoy]

Thanks BTDocteur
That's where I started...
He bought the boat at a bargain price recently. On he test run, the oil pressure gauge showed