I have a new Crown OPDA to replace my old one. I have watched videos and read discussions on replacing. However, I am still uncertain about the TDC. My question is, if a engine is running normally and shut down. Then the engine is manually rotated so a pin can be inserted into the OPDA. At that time, can I assume I am at TDC or do I still need to verify with the timing marks? Thanks.
OPDA & TDC
- Thread starter HiHoSilver
- Start date
When the holes are aligned for the pin in the OPDA, the timing marks should also be aligned for TDC.
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Thanks. When the new OPDA is installed, does it need to be precisely placed in the same position as the old one? Or can it be off by a couple of degrees?
Yes, it should be at TDC, but there is slop in the chain, OPDA/cam gears, etc. You should verify the timing marks or you may have a cam/crank mismatch code thrown.
Only turn the engine clockwise.
It makes no difference where the OPDA points as long as the engine is at TDC, OPDA is pinned, when installed.
Only turn the engine clockwise.
It makes no difference where the OPDA points as long as the engine is at TDC, OPDA is pinned, when installed.
Need advise - when opda is in position to be pinned, the TDC is not exactly aligned (see pic). Should the opda be pinned or should I rotate to TDC and try to adjust the opda somehow? Engine is running ok and a scanner has the crank/camshaft at 4.7 degrees.
Thanks.
Your crank pulley may be coming apart which allows the outer ring with the timing notch to move around.
See if you can move the outer ring and check for cracked rubber.
Also check to see if the pulley had been rubbing on the timing cover.
If so, it needs to be replaced.
See if you can move the outer ring and check for cracked rubber.
Also check to see if the pulley had been rubbing on the timing cover.
If so, it needs to be replaced.
Here is the old timing cover with timing marks:
Hard to tell for sure, but your difference may be about 5 deg on that scale.
Inspect the crank pulley and if it is solid, set the engine at TDC, pull the old one, drop the new one in pinned.
If you want to truly verify if the timing mark is correct, remove num 1 plug and use a long straw to verify it's at TDC.
Hard to tell for sure, but your difference may be about 5 deg on that scale.
Inspect the crank pulley and if it is solid, set the engine at TDC, pull the old one, drop the new one in pinned.
If you want to truly verify if the timing mark is correct, remove num 1 plug and use a long straw to verify it's at TDC.
If crank pulley is ok, pull the old opda out without it being pinned? Would the new pinned opda be lined up to be inserted? My 2005 tj doesn't have the timing plate, just the pointer. Thanks
Would it be possible to pull the old opda being pinned and insert the new pinned opda in the same position? Then use a scanner to relearn the crank/cam difference? Thanks.
Yes, I know, your 05 is the same as my 06, but the timing marks indicate the distance 4 deg would be on the crank pulley. And by the looks of it, it's going to be close to the 4.7 deg yours was off.
Yes, assuming the crank pulley is fine, you set engine TDC by the crank. If the old OPDA is off, it doesn't matter. The new OPDA is pinned assuming the crank is at TDC.
Yes, assuming the crank pulley is fine, you set engine TDC by the crank. If the old OPDA is off, it doesn't matter. The new OPDA is pinned assuming the crank is at TDC.
Hey, no problem. This forum is a great place to learn. I've fought this battle with my YJ which has a distributor which is a little more difficult the first time or so. And have pulled and checked and then replaced the OPDA on the TJ a few times.
Thanks. But if the original opda was pinned, wouldn't the TDC be on the compression stroke? Assuming the engine was running ok originally. Wouldn't one opda cycle be for two crankshaft rotations? I'm just asking. Thanks.
How do you know it's original? How do you know it was installed correctly the last time it was installed? You didn't say why you're installing a new one so we have no way to know what the situation was before you started.
No 1 can be at TDC ON compression or TDC on exhaust. Compression is what you need. Timing marks don't know the difference.
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