oil pressure is jumping around

my 304 the oil pressure just started jumping around changed gage, oil/filter and it still dose it. this doesnt seem right to me be has any one else had this problem?

 

mine at an idle is 20 and about 40 when driving, it does move a little

 

i mean it is 60 at idle and will drop to 40 then to 70 and back to 60 and when i get on it it will drop down to 0

 

I had a similar problem. Mine was jumping around a whole lot and now it sticks a 80 all the time. I thought it was the sending unit, so I replaced it and the same thing happened. Then I realized my guage was bad. Try figiting with the wires on the back of the guage, and see if that helps.

 

Maybe your oil pickup tube has came loose and is sucking air. Does it do anything different when you park it on an incline Front to back?

 

The factory electric gauges are notoriously troublesome. Usually the problem comes from the sender or the wiring ...

I'd suggest you remove the sender and substitute a quality mechanical gauge, like Stewart-Warner, Autometer, etc. Quality replacement electric gauges are ok, but I prefer the quick response time of the mechanical gauges.

 

I've heard horror story's of when the plastic lines of mechanical gages failing and slowly pumping all of your oil out.
I picked up a classic style autometer electric gage it came with the sender and it matches the stock gages. It is quite quick responding to changes also.

 

it doesnt do any thing different when i park on an incline. it dose have a mechanical gage in it

 

Ideally you should have lowest pressure at idle when the engine is hot, and then the pressure should gradually increase with engine speed to some maximum around 60 psi. My brand-new, factory fresh 304 (back in '73) indicated somewhere between 40 and 60 psi all the time. Usually as the engines accumulate miles, the idle oil pressure goes down. Tell us what the hot idle oil pressure is.

If the pressure off idle is really zero, that will destroy your engine right away. I'd suggest you don't drive until you sort it out.

Make sure you have the right amount of oil in the engine. I'd suspect the oil pressure relief spring next, if you're full of oil and you had the same problem with two different oil filters. Could be that the oil pickup in the pan is broken somehow, but that would be surprising.

 

Yeah...I've never seen one break in an AMC...but it sounds so familiar to the ones I have had come loose in Chevy's. It just sounds as if it's getting air from somewhere.

 

it runs at 60 psi when engine is warm. i mean when running it and you get on it it will go to 0 then a few seconds later it comes back up to 60. but at idle it jumps around. i will pull the pan tomorrow

 

thank all of you for the help pulled the pan and found nothing wrong. guess its time for an engine swap

 

Hmmm...might want to try a new oil pump before swapping engines (if you have not already).

 

have a 4.3l sitting on the floor was just waiting for some thing to happen to this one