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Thread: Atomic EFI TBI cast fuel rail leak.

  1. #11


    The reason I'm questioning the WBO2 sensor is the engine sounds happier until the handheld AFR changes from WARMUP to a number and then it starts to sound worse. Plus the AFR numbers are always way too low. A buddy said to try the propane gas trick to find a vacuum leak. I'll try that and see if I can find one. I found it interesting that the MAP readings were below 20 inHg for a good portion of the first startup in the video below after checking vacuum at 2500 RPM. I did try another time with the Atomic EFI set to mild cam and it idled better, but the AFR was always off target. Target is 14.0 idle, 14.7 cruise & 12.8 WOT.

  2. #12


    Got the new WBO2 sensor. As you expected, no improvement. Found two of the three bolts at the exhaust manifold flange (before the WBO2 sensor) were a tad loose, but that didn't seem to improve anything. Tried the propane leak trick to find an intake vacuum leak, can't find a leak. After fiddling with the settings, AFR improved but idle still rough.

    Someone asked if the timing was OK, so now wondering about the timing chain. That check is visible at the end.

  3. #13


    Rotate the engine to TDC and check the position of the rotor in relation to the #1 post in the cap and see if it's off. Use the timing marks to show how far the crank moves before the distributor turns. The video does show a delay, and retarded camshaft timing maybe the cause of the low vacuum. Try a compression test, low readings would also point to a cam timing fault. Then next, the timing cover will have to be removed to check the timing marks. And inspect for a stretched timing chain or damaged keyway.

  4. #14


    If I turn the crank one direction then turn it the other, this is the amount the crank can be turned before the distributor starts to move. Time to get a timing set.
    Click image for larger version. 

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  5. #15


    Yes, that's a problem. It'll be interesting to see where the timing marks are.

  6. #16


    Been busy doing home renos. This weekend got to tear into the CJ and change the chain. What a difference! I have some tuning left to do, but I think that was the root cause. Did a quick distributor adjustment before this footage, and it sounds almost like it did before.

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