Chevrolet had a problem with it's combination sender/switch units used on the 350ci (5.7L) TBI engines in full-size trucks and cars between 1990 and 2000. The sender becomes inoperable due to a loose wire inside the sender itself and makes the gauge erratic. The fix is to replace the sender/switch.
how to install the oil pressure gauge on a Chevy 350 small block
A mechanical oil gauge may bounce if you are low on oil. An electric oil gauge may bounce if the sending unit or the gauge itself is faulty and of course you are low on oil.
1999 Chevy table oil pressure gauge low and check gauges flickering
Right above the oil filter.
Yep!
Screw out the oil sending unit. Put a "tee" back into the hole. Screw in the oil sending unit for the light AND the fitting for the mechanical oil gauge.
what would cause a oil pressure gauge to fluctuate on my 99 Chevy truck silverado i change the sending unit it does it mostly after it warmed up
It is most likely the oil pressure sensor, located on the front of the engine block near the oil filter. There is also a slim possibility that the gauge in the instrument cluster is defective.
most likely a sending unit problem
Yes you can. You will need a oil pressure gauge to do it. You will need to remove the oil sending unit that's back behind the distributor and screew the oil gauge line in it's place and then start the engine and read the gauge. You should have no less then 20LBS at an idle.
You oil pressure sending unit is more than likely defective. Replace it with a new one.
Probably either the sending unit or a loose connection.