Four quarts equals 80% of capacity. It may have needed the other one, you don't say. You trashed the engine running it without oil. The main and cam bearings are so loose it cannot build pressure.
You need to see if it is still in there. You should have stopped when you saw low pressure immediately and checked the dipstick for a level. If this is real you may want to rethink your DIY talents.
4 quarts is an awful lot to be low. Did you put too much oil in?
If the level is normal on the dipstick, then it's likely a bad wire/connection to the the gauge.
You added 4 quarts???
To the left? You mean pressure dropped?
Sounds like running without oil or little if any. The damage may have already been done. Remove the upper valve covers, and pan and inspect. You should not have any sludge, shavings, etc... Check the pick up screen and inspect the oil pump.
Went to the left.What could it be.
