Put a manual gauge on my 1997 to read oil pressure, will get down to 10#, but not the zero it was showing on the dash gauge. what is the next option, new oil pump or perhaps a new electric gauge where the sending unit was. replaced them twice, but still showed no pressure at idle.

If the manual T gauge is giving a higher oil pressure reading than the gauge on your dash - believe the manual gauge.

The oil pressure gauge on your dash receives a signal from an oil pressure sensor. It may well be that the oil pressure sensor is faulty

First you need to find the sending unit. Some are by the oil filter. Most sending units sink current so by taking the lead off and grounding it you should get a reading on the gauge. This will narrow it down to whether it is the sending unit on the engine or the gauge on the dash. Depending on the car there are a bunch more questions to be asked but this is a general answer.

Could be the gauge on the dash. If you really had no oil pressure the engine would be very loud.
A mechanic would check oil pressure with a mechanical gauge to verify.

but where is the fuel pump oil pressure switch located ? my 98 has an oil pressure sending unit with single wire for oil pressure gauge I believe near the filter on passenger side, but I cannot find the fuel pump oil pressure kill switch ?

check it out manually with a pressure gauge ,could just be a high resistance or something ,but check with a manual dial gauge and if low check put the oil pump

Did you compare what your dash gauge read when it was acting up and compare it to the manual gauge at the same time? I know you said you used the manual gauge and it read fine so if you get a proper reading out of the manual gauge and an improper reading out of the dash gauge then your dash gauge needs addressed.

perform a master oil pressure test. this is done by removing the oil pressure sending unit and installing a oil pressure gauge. if the reading on the test gauge is ok, the sending unit needs to be replaced. if the pressure reads low on the test gauge, there may be excessive bearing wear or you may have worn valve guides. good luck!

My guess would be you have a faulty OP sending unit,purdy common on GM!! There are actually 2 sending units,1 controls the gauge and the other go's through the ECM and will shut down the fuel pump if there isn't enough oil pressure! You can or have a mechanic put a manual gauge on it and see what the OP really is running, If it has good OP then,install a new sending unit and Ride that Ride with a Smile!

Have a Great Day!! GMJ

If grounding the dash does not work, try putting a mechanical gauge on it and reading actual oil pressure. Pressure does change while driving, but should not wander. With mechanical gauge, check that running hot at idle (in gear if automatic) pressure should not drop lower than 15psi (I'd rather see 20) High reading should be around 40 -50 but no higher.Low pressure indicates a loss of supply or bad bearing on the crankshaft, high pressure may be caused by sticking pressure relief or restriction in an oil passage.

THE SENDING UNIT WILL BE LOCATED DOWN BY THE OIL FILTER. YOU PROBABLY HAVE AN ELECTRIC PRESSURE SENSOR. THERE WILL BE ONE WIRE CONNECTED TO IT. THE OIL PRESSURE IS USUALLY BY THE OIL FILTER AS THIS IS WHERE THE PRESSURE IS GENERATED FROM THE OIL PUMP. THEY CAN BE HARD TO ACCESS ON SOME ENGINES DUE TO LACK OF SPACE. HERE IS ANOTHER TIP. INVEST IN AN OIL PRESSURE SENSOR SOCKET. THEY ARE A SPECIALTY TOOL AND CAN SAVE YOU SOME TIME IF YOU ARE NOT MECHANICALLY INCLINED. GOOD LUCK