I recently decided I wanted an oil pump priming tool, and I figured the best way to make one would be to use a castaway OEM OPDA. I replaced the OEM one in my LJ with a Crown one at about 48,000 miles, and I saved the OEM as a spare. Since it has relatively low miles, I decided to look for another one to make this tool. After acquiring one, I set to work on making the tool, but before I did so, I decided to compare it to the Crown, to confirm if Crown really had improved the design.
I started by removing the covers off each unit. After removing the covers, I punched out the roll pins in the driven gears and removed them. Here's where I noticed the first difference. The Crown unit uses a thin steel plain thrust bearing between the steel end cap and the gear (NOTE: in all the pictures below that show parts from both units, the Crown pieces are on top, and the OEM pieces are on the bottom):
Next, I removed the shafts from the housing and noticed the second change. The Crown unit has a spiral groove ground in it to transport oil up the shaft:
By the way, if you ever remove the driven gear from the shaft, make sure you mark it first. See the yellow paint on the Crown unit (my spare)? There's a matching spot of yellow paint on the gear on that side because the gear and roll pin hole are indexed. If you put the gear on 180° out, the cam and crank pulses won't be timed properly and you'll likely throw codes!
If you look just to the right of the target wheels in the photo above, you'll see the third difference. On the Crown unit (the top one), there are two steel spacers that simply hold the target wheel up off the bottom of the housing's chamber. In contrast, the OEM unit just has a rubber spacer in that position to hold up the target wheel. Associated with that difference is the fourth difference, inside the housing chamber. The Crown unit has a short bronze bushing inside, with a seal above that, and a rubber washer at the top, and it's not proud of the chamber's bottom, while the OEM unit has a long steel bushing that protrudes into the chamber:
The protruding bushing is the reason there's not a separate spacing riding up there with the OEM unit. The fifth difference is the bushing at the bottom end of the housing. The Crown unit uses a short bronze bushing, while the OEM unit uses a long steel bushing:
At this point, I cut the OEM housing in two pieces in between the upper and lower bushings. I then pushed the bushings and the seal out for an "exploded view" picture:
And then I pressed the lower bushing back in, pressed the target wheel off the shaft, and I now have my oil pump priming tool:
Unfortunately, the shaft diameter is just over 1/2", so I'll have to turn it down on my buddy's lathe so that it can be chucked up in a 1/2 drill motor.
In summary, here's a sketch that shows the differences between the two OPDA designs:
And now you know - the Crown unit really is a better design. The bronze bushings are better than steel, the seal is moved above the top bushing, and there is a spiral oiling groove to drive oil up to the second bushing.
I started by removing the covers off each unit. After removing the covers, I punched out the roll pins in the driven gears and removed them. Here's where I noticed the first difference. The Crown unit uses a thin steel plain thrust bearing between the steel end cap and the gear (NOTE: in all the pictures below that show parts from both units, the Crown pieces are on top, and the OEM pieces are on the bottom):
Next, I removed the shafts from the housing and noticed the second change. The Crown unit has a spiral groove ground in it to transport oil up the shaft:
By the way, if you ever remove the driven gear from the shaft, make sure you mark it first. See the yellow paint on the Crown unit (my spare)? There's a matching spot of yellow paint on the gear on that side because the gear and roll pin hole are indexed. If you put the gear on 180° out, the cam and crank pulses won't be timed properly and you'll likely throw codes!
If you look just to the right of the target wheels in the photo above, you'll see the third difference. On the Crown unit (the top one), there are two steel spacers that simply hold the target wheel up off the bottom of the housing's chamber. In contrast, the OEM unit just has a rubber spacer in that position to hold up the target wheel. Associated with that difference is the fourth difference, inside the housing chamber. The Crown unit has a short bronze bushing inside, with a seal above that, and a rubber washer at the top, and it's not proud of the chamber's bottom, while the OEM unit has a long steel bushing that protrudes into the chamber:
The protruding bushing is the reason there's not a separate spacing riding up there with the OEM unit. The fifth difference is the bushing at the bottom end of the housing. The Crown unit uses a short bronze bushing, while the OEM unit uses a long steel bushing:
At this point, I cut the OEM housing in two pieces in between the upper and lower bushings. I then pushed the bushings and the seal out for an "exploded view" picture:
And then I pressed the lower bushing back in, pressed the target wheel off the shaft, and I now have my oil pump priming tool:
Unfortunately, the shaft diameter is just over 1/2", so I'll have to turn it down on my buddy's lathe so that it can be chucked up in a 1/2 drill motor.
In summary, here's a sketch that shows the differences between the two OPDA designs:
And now you know - the Crown unit really is a better design. The bronze bushings are better than steel, the seal is moved above the top bushing, and there is a spiral oiling groove to drive oil up to the second bushing.
