Oil Pressure Guage Question

[Carl'sMJ]

Actually it is my Oil Pressure idiot light that is the subject of my question. For some reason it is always on when the truck is running, but it is very dim. In the day time you can hardly see it... it is more noticable at night. Sometimes it will brighten up a bit during harder than normal braking.

 

Is this an issue with the sending unit or something else? It's a bit of an annoyance having the light on and I would like to take care of it. Thanks.

[jpdocdave]

only true way to know whats going on is to install an oil pressure tester, a mechanical gauge in place of the sender so you know what the pressure is.

 

if thats not an option, replace the sender to see if its just the sender causing the problem. low oil pressure is not something you wanna play around with.

[Eagle]

The fact thatit's dim suggests it may be a wiring problem. The "sender" for the idiot light is an ON-OFF switch ... there's no setting for "dim." The light should either be off, or bright.

 

Try unplugging the wire from the sender, start the engine, and see what the light does. If it's off, then have someone ground the wire directly to the block and see what happens.

[Carl'sMJ]

I tried it with the unit unplugged and then grounded it directly to the engine block... Both times there was no light.

 

Is there any chance that the sending unit could have been replaced at some point with the wrong unit (i.e. the one for the actual guage)? I'm probably going to grab another unit and try it next. Any other suggestions?

[Eagle]

There was NO light when you grounded the wire to the block? Was the ignition turned on?

 

If you have no light, you have a broken circuit. The idiot light should shine brightly when you ground the wire directly to the block. (I think. If anyone out there has an XJ or MJ with idiot lights, can you confirm?)