There are two types of oil pump drives common to all but the exotic vehicles. The most common is the internal oil pump, which is found in most all of the domestic vehicles. The pump is located within the oil pan towards the rear of the engine in General Motors. It is in the oil pan and towards the front of the oil pan in Ford or Chrysler. Both of these are camshaft driven. The oil pump and pickup tube are located near the main bearing at either end and there is a rod or shaft that runs up vertically to the camshaft.
The early model vehicles that use a distributor use the distributor's drive to rotate the oil pump. The distributor has a gear on the bottom of its shaft. This gear is meshed with the gear on the rear of the camshaft. The distributor has a hollow spot in the bottom of the shaft that contains a metal blade in the center. The oil pump rod has a cut in the end of it that slips over the blade in the distributor, thus locking it in place.
The oil pump side of the rod also has a cut that slides over the blade input shaft of the pump. To keep the rod from coming off of the oil pump input shaft, it has a metal or plastic sleeve placed over it. The later model vehicles with fuel injection that do not use a conventional distributor still have the same block. The hole for the distributor is either blocked off or used for a camshaft sensor. The camshafts are still the same and incorporate the gear on the rear. If there is no camshaft sensor, the oil pump drive shaft or rod has a gear on the top-side of the rod, and it meshes with the camshaft and is capped above to prevent debris from entering the hole.
If a camshaft sensor is used, it has a gear attached to it that is used for spinning the camshaft sensor. The bottom of the gear is the same as the distributor in as much as it has a hole in the bottom with a blade and uses the same type of rod to drive the pump as in the distributor.
The second type is mostly found on the foreign vehicles. The oil pump is located behind the front crankshaft pulley. It has a large gear in a housing. This bolts to the block and is driven by the crankshaft. It is much easier to replace this type of oil pump and it is very dependable.
