The Oil Pump Drive Assembly, O.P.D.A, OPDA, "Ope-Dah" is peculiar to 2005 and 2006 model year Jeeps ONLY. It is driven by a worm gear off the camshaft, and performs two functions: 1) It drives the oil pump down in the sump, and 2) It drives a top mounted "Tone Wheel" that gives a signal to a camshaft position sensor so the computer (PCM) knows when to fire the ignition coils. In essence, it replaces a traditional distributer and is actually very similar in design to one on the bottomside. Zorba's Jeep
OPDA Replacement
It is a known failure point of an otherwise bulletproof engine design, apparently it went through at least one re-design while these Jeeps were in production, but never was considered reliable. Its failure mode as I understand it is caused from lack of lubrication, and it will start to be hard to turn, and/or fail with the famous "Laughing Monkeys" sound (Youtube it, that's EXACTLY what it sounds like!). When it becomes hard to turn, it starts to wear the worm gears on the camshaft and it can get so bad that the camshaft has to be replaced as well!
So enter the aftermarket. The replacement unit by "Crown" is considered a superior design, and is recommended by the TJ forum as well as other sources I consulted. The "Dorman" unit isn't considered as good as the Crown, but either is considered better than the "LDI" original. Some say its OK to wait until it starts to fail, but with just shy of 129K miles on this Jeep, I figured a PM (Preventative Maintenance) approach to be better - why wait for it to grenade on the road or trail?
The OEM OPDA supposedly lasts till around 165K miles, except for those that don't, I've heard of worn camshafts from defective units at under 100K! It was $86 from "Warrior Woman" so let's get it out of there!
Changing it really isn't hard, but you have to pay attention to the details, otherwise you'll get CELs (Check Engine Lights) and codes thrown, and the Jeep entering limp home mode, etc, etc. I didn't have any issues with any of that, thank Goddess; I just took my time and double checked all details as I went. It took me 2 hours, 15 minutes from start to finish. Somebody who had done one before could probably do it in just the 15 minutes!
I watched several Youtube videos on the subject, all of them were "decent", none of them showed all the details I wanted to see! Only one guy bothered to show which direction to hand turn the engine, only one guy - a different one - showed putting oil on the worm gear on the new OPDA to prevent dry running on startup, another guy advocated not removing the plastic locating pin, but rather just starting the Jeep and letting it shear off! I'm quite sure that that's OK because the locating pin is soft plastic, but I wanted to retain the pin for future use. I wasn't successful though...
So without further ado, here's my version of this job. Lots of pictures for something relatively simple.
Here is the only part that I had any trouble with at all, and even this was relatively minor. It is theoretically possible to install the new OPDA without ever taking the top off of it, as long as that plastic locating pin is in place. I did so successfully - the first time. As can be seen in the below pictures, the OPDA is inserted more or less parallel to the engine block, and the worm gears cause the entire unit to rotate clockwise as they engage with the camshaft. The absolute position of the OPDA housing is un-important, it could be installed 180 degrees from the factory orientation and still work fine as long as the tone wheel is pinned in place and the engine was previously rotated to the correct position (TDC, cylinder 1).
Here's all the official numbers...
The new unit. I labeled it with the month and year, the approximate mileage, and the brand name
as there's nothing on the unit itself that says "Crown". The new camshaft sensor was not installed.
Note the white plastic locating pin on the bottomside left of the main housing. Very important!
The OEM unit. Steel bolts into an aluminum housing resulted in stuck bolts.
A dozen hits with a small hammer loosened the bond so I could remove them!
Note small hole in the tone wheel at approximately the 11:45 position. This needs to be
rotated to line up with another hole in the bottom of the housing at about the 8:45 position.
3/4" socket on end of crankshaft, top view.
Bottom view. Engine needs to be turned by hand CLOCKWISE as facing the front...
...which also results in CLOCKWISE rotation of the OPDA's tone wheel.
Checking the alignment of the two holes. You have to get this EXACT.
The object now is to get this plastic pin, borrowed from the new OPDA, into the
bottomside of the housing and up through the corresponding hole in the tone wheel.
However, reaching the hole on the bottomside was problematic - until I removed the oil filter!
Oil filter awaits reinstallation, sitting in the old OPDA's top cover.
Plastic pin installed. Now we know the engine is in the correct position.
Half inch wrench to remove the one bolt that holds the OPDA in place.
Old LDI OPDA removed. Fortunately, it was in good shape and turned easily,
so I don't have any worry about the camshaft worm gears being worn. Note
the flat on the end of the shaft (right) which is what drives the oil pump.
This is the clamp that holds the OPDA in place. Needs cleaning!
The "OPDA hole". The slot in the top of the oil pump can be seen deep inside,
but not in this picture! You have to shine a bright light down the hole.
Stuffed a paper towel in the hole so I could clean around it...
...which was necessary because the new gasket is larger than the old one.
Gasket set in place.
Locating pin re-installed in new OPDA, ready for installation.
Squirted oil on the worm gears so they wouldn't be dry on startup. Just simple prudence.
New OPDA in place.
So I successfully installed the OPDA, and rotated it down - all without removing its top. That would have been just fine, except I pulled it back out to facilitate installation of its hold down clamp, which is notoriously "fiddly" to get in place and get its bolt started. In all this farkling around, I managed to break the plastic locating pin! So then I had to come up with a different way to pin it, which meant I had to remove the top to do so. In addition, I managed to momentarily lose the new OPDA gasket as well. It wasn't on the OPDA, it wasn't in place on the block, it wasn't on the ground under the Jeep - I finally located it sitting on top of the starter!
The oil pump slot "down there" also got out of time as a result of this flail, a BFSD cranked it back to the approximate position needed, and the OPDA dropped back into the slot without any fuss.
To continue:
I then took the Jeep for a test drive, with stellar results. No codes, no limp home, no CELs, no drama. From my research, if there's going to be a problem, it will most likely arise at high RPM, so I ran 4,000 and even 4,500 RPM several times to try to force a CEL if there was going to be one. There wasn't. A bit more driving will cement my confidence, but I think it came out OK! Update: 2 years later, no problems!
Hold down clamp was cleaned, and anti-seize put on its hold down bolt. All bolts were thus treated.
Makeshift locating pin. Unfortunately, the hole in the bottom of the OPDA's body is larger than the
hole in the tone wheel. This means that a pin like this isn't as precise as the supplied plastic one is.
Starting the 2nd insertion. I managed to finagle the hold down clamp and its bolt and
let them "ride" the OPDA on its way down as it rotated. Cussing got the bolt started!
Half inch wrench tightening the hold down bolt.
New and old sensor hold down bolts. Original was a 10mm head, new one was an 8mm.
OPDA top cover. Note the square and round shapes...
...which must mate with the correct shapes on the body. Original sensor re-used.
Everybody knows that if you ask 3 people on the Internet something, you'll get
four answers! However, *ALL* accounts agree: Use the OEM sensor when replacing
the OPDA. The aftermarket ones will either fail out of the box or shortly thereafter.
Job done, oil filter put back in place. Bolts on top of OPDA take a T-25 Torx bit.
One last note: In ALL of the videos I've seen of this job, the first thing the guy does is remove the air pipe between the filter box and the throttle body. There's absolutely nothing wrong with doing so, but its completely un-necessary. I was prepared to remove it the instant it caused me any inconvenience whatsoever - its super quick and easy to remove - but it just never got in my way so it stayed in place. OTOH, I didn't notice anyone else removing the oil filter, but it got in my way so I pulled it...
Read on for the next part!
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