oil sender?

[B192734]

So my 2000 xj got its oil changed on Friday. I did it, and know I put oil in the right place and the right amount. Afterwards my oil pressure fluctuated and at idle would drop to zero. As soon as I gave it gas it would come up to about 30. Now it dropped down and hasn't come back. Runs nicely and everything. Oil is still there and everything...

Could it be my sender? That's what I'm hoping...

[drivers]

thats what i would check but it really sounds like the oil isnt there..... but if its on the dip stick it has to be in the pan,

[B192734]

thats what i would check but it really sounds like the oil isnt there..... but if its on the dip stick it has to be in the pan,

So I have checked a few times just to make sure, and there is definitely oil in it. It's full on the dipstick. I opened the filler cap this morning, and wiped it to make sure it was totally dry, and then I am going to look in a bit to make sure it's got some on it now. I would imagine that would mean that it's working. I am going to pick up a new sender today and put it on just to cover that angle. Hopefully that works, and no issues. Anyone know off the top of their heads what size of wrench that is? Just to make sure I have one on hand...