Once the engine is worn to the point that the oil pressure has dropped, about the only option is to rebuild the engine. If you insist, however, loosen the motor mounts, lift the engine as far as practical, remove the oil pan bolts, drop the oil pan and pull/remove the oil pump and sump siphon. Clean the parts as much as possible paying particular attention to the gasket surfaces and the inside of the pan. Attach the new oil pump, replace the pan, drop the engine back onto the motor mounts, and re-connect the motor mounts. BTW, make sure the oil pump is well lubricated when you put it in. It shouldn't be dry and it would be best if you put some lithium based assembly lube on the gears of the oil pump before you put it all together. Not too much though, just enough to cover all surfaces without closing off the pickup line.
Fig. 19 Oil Pump Assembly
On a 3.8L 95 mustang the oil filter mounts to the oil pump.
Oil pump change
you have to pull the oil pan off the engine to get to the pump as it's under the oil pan, once the pan is off you will see that it's bolted to the engine, take the bolt or bolts out and pull the pump out.
OK there are two ways to change the oil pump on a 1995 Chevrolet s10 2.2L. Because A cross member is made to the frame right under the oil pan you will haft to either take the engine out or take out the motor mounts and jack the motor up for clearence to get to the oil pan its self.
steps by steps how to change a oil pump
You'll need to drop the oil pan to replace the oil pump. There are only 2 or 3 bolts holding the oil pump once the pan is out of the way. The oil pan is the difficult part. The pump is easy. However... Oil pumps seldom fail. If you have low oil pressure it's usually because of excessive rod and/or main bearing wear. Change to a higher viscosity oil before you try to change the oil pump.
The 1995 Pontiac Firebird V-6 engine oil pump is located on the bottom of the engine. The oil pan will need to be removed in order to see the oil pump.
In the oil pan
The oil pump is bolted to the bottom of the engine , inside the oil pan
Drain the oil from your 1995 Chevy Lumina oil pan. Remove the oil pan retaining bolts. Remove the oil pump retaining bolts. Reverse the process to install your new oil pump.
There isn't an oil pump relay. The oil pump is driven by the crankshaft.