Why Install A New Oil Pump?

One, it's possible that the old oil pump had experienced some wear, and was not delivering enough oil pressure. Two, it's easy to do at this stage, and doesn't cost too much. Basically, replacing the oil pump is cheap insurance, and is recommended by many mechanics and engine rebuilders.

The new oil pump and pick-up tube, which are sold separately. These two parts cost about $60.Note the small white part... this is a nylon connector that joins the oil pump shaft to the intermediate shaft, which is driven by the bottom end of the distributor shaft.

With the 4.3 liter V6 engine, a new oil pump and pickup tube are sold separately ( I think that's because the GM 5.7 liter V8 uses the same pump, but a different pickup tube).

The pickup tube is pressed into a hole in the pump body, but that is not an easy job. In the factory, a simple press could do this task in a few seconds, but I don't know of any common mechanic's tools that will allow you to gently push on the curved pickup tool. Don't even think about hammering the tube into the pump... you'll risk puncturing or creating a kink in the tube.

After thinking about this for a while, I decided to make a simple fixture to allow a large C-clamp to push on the flared section of the tube. It worked for me.

Jig For Installing Oil Pickup Tube:

I made this little part from 3/4" iron plumbing pipe. This is just a piece of pipe with a notch cut out.

cut this on a metal-cutting chop saw, but this could be made with a hack saw or reciprocating saw.

and cut a little less than half of the diameter away, so the pipe would wrap more than half way around the pickup tube. I cut the notch first (the scrap of pipe was about 3 feet long) before cutting the overall length, which was about 2-3/8 inches.

The red arrow points to the homemade jig.

After I got the pickup tube started in the hole in the oil pump bottom plate, I placed this rig in a 6-inch C-clamp. I held the C-clamp in a bench vise.

I made sure the tube was well oiled so the metal would slide without galling.As I tightened the C-clamp, I tapped on the bottom plate with a small hammer to make sure the tube entered straight.

Note that I used a 6" C-clamp because my bench vise only opens to about 4 inches. If I had a 6" vise, I would've used that.

I ended up using a hose clamp (red arrow) to keep the jig from spreading open or slipping off the pickup tube. This worked well for me.

After tinkering with various placements inside the jaws of the C-clamp, I finally found a position where the tube just slid into the hole with only modest clamping effort.

Assembling the pickup tube and oil pump was a royal pain in the a$$.

filed off some burrs around the edge of the bottom plate. These may have been created by pressing on the edge with the C-clamp.

Then  used compressed air to blow off any particles, and I wiped the surfaces clean with a paper towel and brake cleaner.

IMPORTANT:

I packed the space around the oil pump gears with petroleum jelly.

I've read that a gear-type oil pump needs to be pre-filled with something (i.e. primed) or it might not be able to suck oil upwards and push it into the engine. The pump cavity can be filled with gear oil if the pump is NOT going to be tipped upside down. Otherwise, petroleum jelly needs to be packed around the gears.

removed the intermediate shaft from the old oil pump by just pulling it straight off, then  slipped the nylon collar over the end of this shaft and pressed it onto the shaft of the new pump.

poured some gear oil down the output hole (red arrow) of the oil pump.

installed the oil pump while the engine was right-side-up on the engine stand.

The drive shaft goes through a hole near the edge of the rear bearing cap, and the pump base fits over two alignment pins. Then the pump bolt is installed.

 tightened the bolt to 65 foot-pounds.