I changed the oil in my TO-30, and the pressure went to “0” and stayed there. What could cause this? April 12, 2016.
Is it possible you got the wrong oil filter? If you installed an oil filter for a TE/TO-20 it would likely block all oil flow. The flow of oil in the TE/TO-20 oil filter is just the opposite as that for the TO-30 oil filter. The correct oil filter for a TO-30 is a Fram C-3P or C-3. the C-3P being heavy duty, and preferred.
Other possibilities include a plugged oil galley in the block or cylinder head, a plugged oil line going to the oil pressure gauge, a defective oil pressure gauge or a plugged oil pressure gauge, a defective or stuck pressure relief valve in the oil pump. It will take some time to check out these possibilities, but until you determine the cause of the loss of oil pressure, don’t run the engine for other than very short periods to run tests. Since the oil filter was the only thing changed other than the oil, that is where I would start.
One other possibility is the oil pump lot its prime, this is unusual, and usually only occurs when the engine, and oil pump have been rebuilt. A simple way to prime the oil pump is to disconnect the oil line at the back of the oil pressure gauge, or at the block, and use a pump oil can to pump oil into the engine until you hear it running into the oil pan. You can use a short piece of rubber hose between the oil line, and the pump oiler to get oil under pressure into the engine.
You can check the oil gauge by temporarily connecting a good oil gauge to an oil line connected to the fitting in the side of the block.