Oil pressure switch

[b3uhbp]

Hello all. Yesterday my oil pressure gauge dropped to zero then came back up but was very erratic and showing very low pressure. There was plenty of oil in the crank case so I was pretty sure the oil sending unit or pressure switch were bad so I replaced them both. Everything seemed fine, showing 55lbs psi, higher than I had ever seen on this jeep, and the needle was holding very steady. Then all of a sudden the needle became erratic. What’s going on? I’m clueless on this one.

 

[Torxhead]

You could add in a mechanical oil pressure gauge by teeing into the existing oil pressure sending unit. From there you could research out the electric gauge problem. The oil pressure send unit and gauge both require grounds, make sure those are hooked up. From there it could be a bad wire or send unit.

 

[b3uhbp]

You could add in a mechanical oil pressure gauge by teeing into the existing oil pressure sending unit. From there you could research out the electric gauge problem. The oil pressure send unit and gauge both require grounds, make sure those are hooked up. From there it could be a bad wire or send unit.

Good advice. I’ll check all wiring and see what happens. The odd thing is that it was working so well initially. Even though it is unlikely I did replace the sending unit. Also, the two blade plug that’s at at 90 degrees to the sending unit, what does it do? I’m. Pretty sure it is just a switch but for what? There’s no idiot light on these old cjs. Did it work with the old computer in some way?

 

[Lumpy Grits]

Do not trust the OEM, OP setup-ever.
He's a 'fix'.......
Oil Pressure Gauge. Black Dial, Mechanical Oil Pressure Gauge.

BTW: IF you had truly lost all OP. Your valves would have sounded like someone pouring marbles on your hood.

LG

 

[Torxhead]

b3uhbp, that two bladed plug is some sort of oil pressure switch that is tied into the computer. In a wiring diagram for my '86, it has a red and red w/tracer wires on it.

 

[b3uhbp]

Do not trust the OEM, OP setup-ever.
He's a 'fix'.......
Oil Pressure Gauge. Black Dial, Mechanical Oil Pressure Gauge.

BTW: IF you had truly lost all OP. Your valves would have sounded like someone pouring marbles on your hood.

LG

I didn’t know that but it makes perfect sense. I was looking for a high temp but I pulled over fast and shut it down and checked the oil level.

 

[mtnwhlr]

Do not trust the OEM, OP setup-ever.
He's a 'fix'.......
Oil Pressure Gauge. Black Dial, Mechanical Oil Pressure Gauge.

BTW: IF you had truly lost all OP. Your valves would have sounded like someone pouring marbles on your hood.

LG

This the rout I took when mine went out. I trust the mechanical more then the OEM. I went with the white face one.

 

[b3uhbp]

b3uhbp, that two bladed plug is some sort of oil pressure switch that is tied into the computer. In a wiring diagram for my '86, it has a red and red w/tracer wires on it.

I replaced the sending unit but also checked all the wiring based on your suggestion. A guy at Summit Racing also suspected a wiring issue. Interesting you mentioned the two blade switch and the old computer. That’s exactly what the guy at Summit said this afternoon as well. It would never have occurred to me. I removed the computer and the associated wiring about a year ago. I disconnected the switch with engine running and it had no impact on the gauge. It’s working well right now but I’m suspicious. I’ll provide an update in a few days.

 

[Lumpy Grits]

It wouldn't hurt for you to run a dedicated GND lead from the dash panel to the NEG(-)battery post.
LG

 

[b3uhbp]

It wouldn't hurt for you to run a dedicated GND lead from the dash panel to the NEG(-)battery post.
LG

That’s a great idea and easy. I will get that done. Thanks

 

[b3uhbp]

You could add in a mechanical oil pressure gauge by teeing into the existing oil pressure sending unit. From there you could research out the electric gauge problem. The oil pressure send unit and gauge both require grounds, make sure those are hooked up. From there it could be a bad wire or send unit.

I promised to provide an update so here it is. The oil pressure gauge is working perfectly. I replaced the original connector with an eyelet and secured it with the nut on top of the sender. Nice steady needle showing 20lbs at idle and 40lbs at cruise speed. Pretty sure it as a grounding issue. Thanks all.