Yesterday I changed out the oil pan gasket on my 2000 Suburban. I let the silicone in the corners of the pan dry over night. This morning I fill er up with oil and start her up. The low oil pressure light came on and the oil pressure gauge won't move from 0.

My guess is the o ring I put on the oil pump pick up tube. The old o ring had flat edges on the inside and the outside. The new o ring I got from the dealer was red instead of black and is a traditional "round" o ring with no flat spots.

I let the engine run for a minute or a little longer and then I shut her off in disgust.

I am assuming tear it all back down, get a new "flat" o ring at the dealer hopefully tomorrow and then we are back in business? Maybe I'm missing something? It seems the repair went well and there are no leaks.

 

Are you sure that the flat sides on the o-rings aren't due to it taking a set since its been installed in the engine for quite a while?
Unless the o-ring was the wrong size, I doubt that it was the cause of your zero oil pressure. I would check the oil pressure sensor.

 

Two different styles of o ring. Definitely not just mushed down. Diameter was the same though.

 

How did the motor sound despite the gauge reading?

 

It sounded rough. It also stalled the first turn of the key which it only does if I change the fuel filter. I have the valve noise always on cold start up. It goes away after about 30 seconds.
Update : Decided it is the o ring so I've begun tearing it down again. In draining the oil I found the new oil filter empty.
Feel free to add anything while I'm out under the truck.

 

Do oil pumps need to be primed??

 

Years ago a friend of mine replaced oil pump on a cavalier. He had the same problem when first running engine. I suggested he pack the pump with grease as it is not a self priming pump. He said he had no grease but used Vaseline and it did the trick. So if they haven't changed type of pumps this very well might be your problem. Good luck

 

How it ended:
I went to a Chevy dealer Monday morning in search of the flat o ring. He found mention of it in the computer but could not find the part number. I ended up using the original as it still looked good.
After I got everything put back together the oil pressure is back to normal.
Not sure what to think about the deal but I'm back in business.

 

Always so comforting when the professional can't help you. Thanks for the update - interesting that such a small change makes the difference - or coincidence??