I have a problem. On my '94 truck, the first time that I start it and warm it up the oil pressure is normal according to the gauge. Once I turn it off and then restart it, it seems lower than normal. I'm thinking that it's the sending unit and/or the gauge itself, since it's very erratic and changes every time that I start it. But if it's not, what could it be? Truck only has 84,000 miles and sounds perfectly normal (except for the timing belt idler pulleys, which need to be done).
Update: I'll post pics of it tomorrow

 

The pressure sensor may be messed up. I assume you are taking into account that after a cold start, the idle is higher thus more oil pressure compared to a warm idle.

 

What I mean is that when it's at operating temp, the oil pressure is normal. But when I turn it off for say 10 minutes, and then go back outside and restart it, the gauge shows a much lower reading

 

mine uit working all together, I just keep checking the oil, and the 3.0 abides

 

Here's the pics, all are with the truck at operating temp. These are just examples since I didn't actually start the truck. 1st one is at 2000 rpm, 2nd one is at idle

 

And these are when the truck has sat for a bit and was restarted, still at operating temp. 1st is at 2000 rpm, 2nd is at idle, see the difference?

 

This is normal. When the oil is cold, it's much thicker and results in a higher indicated oil pressure. I don't know if this is because more of it gets pumped through the gears in the pump or if the viscosity difference... I see the same thing on my aftermarket gauges.

 

well first things first get a oil P gauge and see what the pressure is realy doing and rule out the pump. Change the oil.

Now if it's the sender or the guage you can perplace them with stock or go aftermarket.


I resently just had a oil pressure problem on my new rebiuld / LC oil pump
I was seeing 100+psi cold 70 warm. the relef valve in the pump seems 2 be hanging up.
I replaced it with the one from the EB kit and now have 40-60PSi idle/rpms

 

I have the same thing with my diesel. You can drive the truck for a while and it will go down but not too much and this is from the oil warming up and thinning some. But even if I shut the truck off for 2 mins or so and come back out and start it again the gauge will read lower after I start it than when I shut it off. Exactly the same thing as you are dealing with. I have yet to check it with an actual gauge but I'm glad someone else is experiencing the same thing as me. Could just be a screwed up sending unit or gauge. Just have not had time to get a mechanical gauge in it yet.

 

I don't think that thats the problem, there's no way that the viscosity of the oil would change that quickly

 

i have the same problem im in such bad shape im thinkingg about taking my 94 in my cars radiator gets extremely hot which i do think causes a oil pressure drop my oil pump is new also and my water pump pullley doesnt budge so i dont think thats the problem please email me if u get an answer at simpsons721@yahoo.com

 

It changes very quickly with heat. (depends on oil type too)
The oil gets hot before the rest of the motor does..

 

The viscosity can't change that much from just letting the engine go into heatsoak for ten minutes. The gauge reads lower once the engine is restarted, which is why I don't think that the problem can be attributed to viscosity

 

What would low oil pressure indicate anyway? I think it has something to do with worn bearing or something like that, but I'm not sure

 

any update ? did you get/use a gauge

 

the oil will get hotter , when a motor sits it tranfars the heat from the steel block the water and the oil will be like a heat sink it will get much hoter the first 5 min or so after shut down try it and see how much hoter it gets if you look at the temp after a min or 2 i will be hotter the block is tranfaring the heat to the oil\water . so it will lower the presure. what will it do if you drive it for a bit and see

 

can you put a bigger spring in the buy pass some pumps you can

 

I haven't had a chance to do it yet, but I plan to soon