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Thread: Help understadning my CJ7 SBC datalog

  1. #1
    Fuel Injected!
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    Help understadning my CJ7 SBC datalog

    I have posted this under Unhappy CJ7, but would like to re-iterate my help needed. History - 70s 350 with TBI installed in 2014. .195 intake heads, 30 over pistons, mainly stock, but whole assembly balanced with TH400. Ran great, but now lacking power under acceleration. I got the Tunerpro so I can read more than a key turn for the OBDI. I attached a log file. Idled, went down the road with mild accelerations, WOT a couple times to feel/show the stutter. Idled at a turn, geared down and WOT through 1-3. Once home, I put it in park, and idle went through the roof!

    Any help of what to look at, or try next, my wife and I would really appreciate it. We love driving this Jeep, but have not been able to enjoy it for most of the summer.

    Diagnosing by wallet, and some manual reading diagnosis has not panned out. I'm savvy with engines, some electronics. New to the Tunerpro, I am asking for support! Moral support if any.

    Thank you for your time!!
    Attached Files Attached Files

  2. #2
    Super Moderator dave w's Avatar
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    Is the data log for the 1227747 ECM?

    dave w

  3. #3
    Fuel Injected!
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    1227747 is correct

    Hi Dave, My apologies for not noting this. You are correct

  4. #4
    Super Moderator dave w's Avatar
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    Are the BPW and SA Hacks setup in the .bin file? ---- BPW and SA data are very useful.

    Knock Accumulations are unusual. --- Maybe experiment with temporarily disabling knock? Monitors show a saw tooth, normally flat line with an occasional spike.

    Mostly running rich. ---- Maybe an injector is dripping? Check injectors with a timing light to verify spray pattern.

    dave w

  5. #5
    Fuel Injected!
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    I do not have the .bin file installed at this time. I only did the .adx so I can log some data. One thing I did not do was increase the latency in the USB to 1msec. Once I do this, I can re-log data (maybe it can smooth out the charts). I rebuilt the TBI, and did see a nice spray pattern about 1 month ago, but can check again. I am unfamiliar with the BPW and SA Hacks.

  6. #6
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    Quote Originally Posted by Dlxman View Post
    I have posted this under Unhappy CJ7, but would like to re-iterate my help needed. History - 70s 350 with TBI installed in 2014. .195 intake heads, 30 over pistons, mainly stock, but whole assembly balanced with TH400. Ran great, but now lacking power under acceleration. I got the Tunerpro so I can read more than a key turn for the OBDI. I attached a log file. Idled, went down the road with mild accelerations, WOT a couple times to feel/show the stutter. Idled at a turn, geared down and WOT through 1-3. Once home, I put it in park, and idle went through the roof!
    if it ran good before and now doesn't it's time to go back to the basics, fuel delivery & spark. spark plugs, cap & rotor look good? what's your fuel pressure? have you verified your base timing? not saying scanning won't help but there are basics you should check especially if you haven't touched anything since you got it running 8 years ago.

    on the note of "rebuilding the tbi". i don't like this term as it usually entails replacing a few orings and cleaning the unit. hardly a rebuild. did you check the throttle shaft for play? i haven't seen one in the last 10 years that couldn't use throttle shaft bushings. i recently am a BIG fan of taking the injectors to a professional shop that has an injector cleaner (ultrasonic) & test machine . getting a flow report is an excellent bonus as well. i don't guess at this stuff any more this is my recipe for a "rebuilt" TBI

  7. #7
    Fuel Injected!
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    Hi Tato, thank you for your input. All the basics have been checked as good or new. Cap and rotor were replaced last year with a bad connection to the ignition on module under the GM HEI cap. I have completed vacuum leak tests on all areas including the throttle shaft to end up clean! Which is good. As Steveo had mentioned, originally the injector spray pattern was good after the "cleaning and gasketing" of the TBI.
    I checked it this evening, and behold the right (passenger side) put out no fuel. This was after warm up and closed loop. The left side had a cone, but seemed a little wet, not a fine(ish) mist. I did swap the RH to LH connectors to see if it was in the wireing, but no difference. Not sure if this was the right way or not. Regardless, I am going to pull the injectors and either clean or replace them.

    I will let you know by this time next week if it was successful, as it will take time to get it done, and be abck in town to try it out.

  8. #8
    Fuel Injected!
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    good stuff! i just ran into this with a set of recently cleaned injectors. if injector is not spraying take a small hammer and tap the injector pod repeatedly while the engine is running. have brought 2 injectors back to life this way. i recommend finding a set of factory injectors and getting them cleaned, i have heard new injectors are made differently and can affect the tune/require further tuning
    Last edited by tayto; 08-25-2021 at 02:49 AM.

  9. #9
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    Hi Tato, thank you for your input. All the basics have been checked as good or new. Cap and rotor were replaced last year with a bad connection to the ignition module under the GM HEI cap. I have completed vacuum leak tests on all areas including the throttle shaft to end up clean! Which is good. As Steveo had mentioned, originally the injector spray pattern was good after the "cleaning and gasketing" of the TBI.
    I checked it this evening, and behold the right (passenger side) put out no fuel. This was after warm up and closed loop. The left side had a cone, but seemed a little wet, not a fine(ish) mist. I did swap the RH to LH connectors to see if it was in the wireing, but no difference. Not sure if this was the right way or not. Regardless, I am going to pull the injectors and either clean or replace them.

    I will let you know by this time next week if it was successful, as it will take time to get it done, and be back in town to try it out.

    How do I know which injectors I have? No markings....??? TBI #17089018 3459 JWZ
    Last edited by Dlxman; 08-25-2021 at 03:17 AM.

  10. #10
    Fuel Injected!
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    that # appears to be the number stamped on the TBI unit itself. if the injectors have no number etched in the top or paint markings the only way to determine what they are is to get them flow tested @ 13 or 14 psi

    http://www.gearhead-efi.com/Fuel-Inj...d-part-numbers

  11. #11
    Super Moderator dave w's Avatar
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    Perhaps a picture of the EXTREMELY UNUSUAL Knock (sawtooth pattern) will be helpful?

    dave w

    Knock.jpg

  12. #12
    Super Moderator dave w's Avatar
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    Perhaps a picture of the EXTREMELY UNUSUAL Knock Accumulation will be helpful?

    dave w

    Knock.AccumulatorJPG.JPG

  13. #13
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    i would focus on the injector that's not firing personally. 4 cylinders not firing might be what knock sensor is detecting.
    Last edited by tayto; 08-25-2021 at 07:06 PM.

  14. #14
    Fuel Injected!
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    Hello All, I have had the injectors ultrasonically cleaned and replaced. Still runs poorly after warm-up. The data log from 8/26 is attached. I also have no idea why the sawtooth pattern exists. Could this be a bad ground?
    Checking the spray pattern with a timing light (cyl 1), I could only see the one injector spraying (again), but do both injectors fire simultaneously, or do they alternate? I could see fuel hitting the port of the throttlebody on the injector that appears not to be firing.
    I have two new matched injectors on the way, but wont ship until after Sept 1.

    Thank you once again for your support and suggestions. I'm not one to give up or afraid of hard work!!
    Attached Files Attached Files

  15. #15
    Super Moderator dave w's Avatar
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    I have only looked at the first data log posted in this thread. It seems odd to me the engine would be running rich with only one injector working.

    Perhaps a quick timing light test of unplugging one injector at a time would be a worthwhile experiment?
    Ignition key off ... unplug one injector ... start the engine and check spray pattern with timing light ... repeat test on other injector.

    Seems one of the logical outcomes of the above test might be . . . if one injector is not working ... the engine won't start?

    Sawtooth knock pattern, possibly measure the resistance of the knock sensor. Remove the electrical connector from the knock sensor and measure from where the were the electrical connector was plugged into (center of knock sensor) to ground.

    dave w

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