95 c1500 gauges drop when i turn on the lights.

[Irondice]

Really guessing here as it sounds like your new-to-you truck has multiple demons that need exorcising, but my wild guess is a combination of problems - fuel pump relay bad, as well as oil pressure sender/switch combo bad, causing interruption to the fuel pump circuit. It only takes one of these operating correctly to successfully power the fuel pump circuit, but if both are flaky, there you go. It sounds to me like the truck may be depending on the oil pressure switch and they tend to get flaky where they'll read low/zero.

I'm not 100% sure on this but I think the fuel pump relay on a '95 isn't a common type with any of the other ones in your electrical center that you might swap as a quick test, and while I don't normally like to recommend just shotgun replacing stuff - a fuel pump relay is really inexpensive and may be worth spending a few bucks on just as a test.

Richard

Fuel relay is next on the list for today. Also going to replace the in-line fuel filter. Thanks!!

 

[Irondice]

OK, so we know the oil pressure doesn't depend on the electric circuits, but the oil pressure gauge does. So the gauge may be in error for reasons yet unknown.

We also know that the oil pressure depends solely on the mechanics of the engine, and will drop if the engine RPM drops or dies, or drop if the bearing clearances become excessive, etc. But otherwise, if the oil pressure wasn't a problem before, it's not a problem now. The gauge's performance may have changed for some reason.

As for the engine hesitation, it's time to investigate.

Are there any codes set?

@someotherguy's remarks are noteworthy too.

The truck doesn't have check engine light on. And the port to check codes is different than my scanner and i can't connect it. Oil pressure switch is the one behind and underneath the distributor cap correct?

 

[1998_K1500_Sub]

Oil pressure switch is the one behind and underneath the distributor cap correct?

Yes, beneath the distributor.

 

[1998_K1500_Sub]

The truck doesn't have check engine light on. And the port to check codes is different than my scanner and i can't connect it.

Check the codes by using a jumper on the ALDL connector. Google “1995 gm jumper check codes”; instructions for doing this can be found. There may be codes even though the SES isn't illuminated.

 

[Irondice]

Yes, beneath the distributor.

Ok swapped out the oil sensor for a new one... not easy to wiggle wrenches back there. Next is the fuel relay.