4.0L swap - No Oil Pressure

[belovedb2]

After completing the 4.0L swap into my 86 B2 and completing the gage wiring I started the engine and did not have any oil pressure on the gage. I then put a ohm meter on the sender and it did not indicate any pressure. I then unscrewed the oil filter to see if it was filled. It was. I then pulled the pressure sender and applied some pressure. At 7 PSI it intergized. I have verified that I am not getting oil pressure.

When I had the 4.0L engine out I pulled the oil pan, cleaned the inside and put on a new gasket. When looking at the shop manual once again the only this I missed was not priming the oil pump. Could this be it?

 

[AllanD]

I think I know what's going on here.... bear with me for a moment...


The oil pump will self prime but what you have is an instrumentation issue
and a slight lack of understanding on those things work... which I'm going
to try to correct.

Let me lead you back through the information you've provided and see if you see the problem...

You applied pressure to the "sender" and at 7psi it "energized".....

Think about that for a moment....




the oil pressure "sender" on a 4.0 is NOT a "pressure sender" it's a "pressure sensor emulator". because people asked WAY to many questions at the dealer about the exact (variable) position of the needle on the early explorers.

And rather than answer the flood of stupid questions....

It is a fixed resistance and a pressure switch that CLOSES contact when pressure is applied
so the light goes on when there is pressure.

an early pressure switch intended for an "idiot light" is closed contact (to turn on the light) when there is ZERO pressure up to 7-10psi or so.

It would be energized as you call it sitting in the box, pressure applied turns the light OFF.

What you need is a pressure switch for an '86-88 if you have a tach
OR if you don't have a factory tach you need an actual guage pressure
sender for a 1983-88.

AD

 

[belovedb2]

I have purchased and installed a pressure sensor (really a switch that entergizes at 7 PSI) from a 86 B2 so that it is compatible with the gage. The gage uses a 5 volt regulator (vibrating bimetal type) and when the sensor or really a switch is entergized the gage goes to normal. I have verified that the sensor does energize at 7 psi by applying that pressure to the sensor and measuring the resistance across the terminal and ground. At 7 psi it switches. It works. I have also verfied that the switch does NOT entergize when in the engine with the engine at idle.

 

[adsm08]

Ok. Lets do this right.

Beloved: Step 1: stop saying "intergized" and "entergized". Stop making up words. English is your first language, go learn it.

Step 2: Go buy a mechanical pressure gauge, hook it up, and find out IF you have pressure. The pump will self prime, as AllanD said. Also, your gauge, it's still, essentially, an idiot light.