Oil pressure gauge issue ??

[Torque_Nut]

I have a question regarding the oil pressure gauge in a 2005 K2500 Suburban. A local dealer has this vehicle with low miles (~27K) and the 8.1L engine. Went to look at it today and was ready to test drive it. Before going, I checked the oil (and other fluids) and all were full and looked relatively fresh. After starting it up I noticed that the oil pressure was still on zero. After about 30 seconds, still no pressure and I shut her off. The dealer said he never noticed that and that it had been driven a few times over the past week with no problems.(??)
I did notice that when I insert the key to start the engine and turn it to the on position just before the starter engages that all of the dials jump EXCEPT the oil gauge. This "jump" is normal on all vehicle that I've seen. Therefore, I suspect that it is a faulty sender unit or something with the guage. A mechanic said the same and is going to check it out tomorrow and notify me. My question, does this sound like the real problem? As I said it has very few miles and has a clean CarFax report (for whatever that's worth). Is there anyway to check if there has been a real oil pressure problem. Again, the reading was ZERO, not just low and the guage never jumped when turning the key to the on position (not start).
What should I request from the Dealer Mechanic if he says that it was just a sender unit problem? Error Code printouts to confirm? Any suggestions?
Thanks for you help.

[Cusser]

[quote=Torque_Nut;5926770]Is there anyway to check if there has been a real oil pressure problem. Again, the reading was ZERO, not just low and the guage never jumped when turning the key to the on position (not start).
What should I request from the Dealer Mechanic if he says that it was just a sender unit problem? QUOTE]

The easiest way to check your problem would be to screw in a new oil sender switch and see if that takes care of it. On my '94 5.7 liter/350 that's only about a $25 part. If the mechanic says bad sender, and new sender fixes it, let him replace it.

To see if it's really an oil pressure problem, a mechanical gauge can be temporarily screwed in, and the engine rpm raised.

If you have oil pressure and an operable sending unit, then the gauge itself needs to be explored.