Oil pressure gauge issue...
 

Alright so I've had my truck for almost 2 months, all the factory dash gauges worked great. The truck has a newer fresh rebuilt 350 in it, and runs valvoline VR1 20W50 oil in it which i know is quite thick. So when cold the truck runs at 75-80 lbs of pressure on the mechanical gauge i also have, until it heats up and will then run at around 60-65psi of pressure when cruising. so obviously the stock gauge only goes as high as 60psi of oil pressure so it was basically maxed out and then some when it was cold.
so 2 questions.
Could too much pressure break the stock electrical gauge? it seems to be stuck at the first line, it doesn't make a difference if the truck is running or not it does not move. all grounds are good and the connection at the sending unit is fine.

is this a bad sending unit or a faulty gauge?

Re: Oil pressure gauge issue...
 

Of course it could. Why on Earth would you run such thick oil?

Re: Oil pressure gauge issue...
 

I didn't run it. i'll be changing to to a 10w40 weight this weekend. I'm not sure why the previous owner chose to run such thick oil. i'll eventually check the gauge and see if its the sending unit or the gauge itself. I'm hoping just the sending unit went bad.

Re: Oil pressure gauge issue...
 

I do not think too much pressure can break the stock gauge. the gauge is operating on the resistance reading coming from the sender on the block.

Since you have a 60 psi gauge, I assume you have a 60 psi sender, so if you have 70 psi, its just going to max out the gauge. (my dads 79 would ALWAYS max the oil psi out on cold starts for 20+ years, still working fine).

did you try tapping the gauge plastic face? My 87 oil gauge sticks sometimes and I can smack it and it moves and operates again.

I'm not certain for the oil gauge, but i know for the gas gauge a quick test is to remove the sender wire and the ground it out. I forget which but the gauge should swing from one extreme to the other.