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Intermittent "puff Puff" At Exhaust

Discussion in 'Early CJ5 and CJ6 Tech' started by TonyM, Feb 21, 2020.

  1. Feb 21, 2020
    TonyM

    TonyM Member 2023 Sponsor 2022 Sponsor

    Middle Tennessee
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    1956 CJ5, F134, 6v... Some background... Over the past 4-5 months I haven't been able to drive the CJ5 much but during that time I've done a bit to the rig including rewiring the entire thing (w/Walcks NOS type harness), installing a Pertronix 6v electronic ignition module (and manually adjusting the timing a tad to accommodate it) and troubleshooting a fuel pump issue that eventually lead to an NOS fuel pump install the other day.

    Now that I'm ready to enjoy the jeep, I have an intermittent "puff puff" at the exhaust. A friend and old jeep expert thinks that the "puff puff" may be indicative of the engine needing a valve adjustment. He's 1000 miles away so I've been running things by him via video and phone. Because he's been "right on" with these long distance diagnosis in the past, I assume he's right in this instance as well BUT I wanted to see if there's anything else I should try before physically diving into the valves. I just put 9 gallons of fresh no-ethanol fuel and a bottle of Heet in the fuel tank to get out any condensation/water from the rig sitting over the past 4 months and freshen up the existing no-ehtanol gas. I'm not big on additives, but is there something else I should try in the oil or fuel if it is a slightly stuck valve?

    For what it's worth, after adding the fuel and Heet I drove the jeep for about 10 miles the other night and didn't notice any hesitation while accelerating or stuttering while cruising at any speed, but the "puff puff" is still there...

     
    Last edited: Feb 21, 2020
  2. Feb 21, 2020
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    In my experience that indicates a burned valve, perform a compression test or preferably a leakdown test to verify.
     
  3. Feb 21, 2020
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    If it's a noise puff puff sometimes idle air screw adjustment can help.
     
  4. Feb 21, 2020
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Agreed, if it is pronounced.

    OTH, my f-heads seem to have a regular heart-beat puff-puff that is harmless.
     
  5. Feb 21, 2020
    TonyM

    TonyM Member 2023 Sponsor 2022 Sponsor

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    here's what the "puff puff" sounds like (added to original post as well):
     
    Last edited: Feb 21, 2020
  6. Feb 21, 2020
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    To me it sounds like your idle is a bit high. You might try dropping it just a little (very little) first.
     
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  7. Feb 21, 2020
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    Did you increase the timing or is it @ 5 BTDC?
     
  8. Feb 21, 2020
    TonyM

    TonyM Member 2023 Sponsor 2022 Sponsor

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    thanks for the advice! had to increase the timing a little (went by ear) for the Pertronix, but I will dial it back a bit (rotating dizzy slightly clockwise) towards 5 BTDC tomorrow when I can get back into the garage. will adjust the idle speed first.
     
  9. Feb 21, 2020
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    I would do the timing first, then make any idle speed or air mixture adjustments after that.
     
  10. Feb 21, 2020
    TonyM

    TonyM Member 2023 Sponsor 2022 Sponsor

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    Will do, in that order - thanks!
     
  11. Feb 21, 2020
    CHUGALUG

    CHUGALUG Member

    Silverton, OR
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    Scare up a 4X6 note card hold it in two fingers along one end then move it over the exhaust pipe as the engine is running. To act like a damper. If it is sucked up tight against the end of the tail pipe at all (will be like a slap just for an instant) you have a Valve or more either out of adjustment or burned. Either way the card slapping against the end of the Tube denotes a Valve problem. Old School way to check valves when buying a used car. You could also connect a Vacuum gauge to the port on the intake manifold and then google a Vacuum Gauge chart to see what thats telling you. timing should be done with a timing light.
     
  12. Feb 21, 2020
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Vacuum gauge is the best bang for the diagnosis buck going, but almost no one thinks to use one.
     
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  13. Feb 21, 2020
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Will a 3x5 card work??? :lol:
     
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  14. Feb 21, 2020
    TonyM

    TonyM Member 2023 Sponsor 2022 Sponsor

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    Never heard the card trick before - will do that tomorrow as well. Thanks guys!!
     
  15. Feb 21, 2020
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    Certainly wouldn't hurt to try it if the other things don't work. Possibilities of a vacuum problem can very easily get over looked.
     
  16. Feb 21, 2020
    DirtRoad61

    DirtRoad61 Member

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    Mine had similar issue. Motor would stall out around 35 mph. PO had timing way to advanced.

    Also setting the valves was easy and made a huge difference.
     
  17. Feb 22, 2020
    CHUGALUG

    CHUGALUG Member

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    Yes a 3x5 will work I'm just a 4x6 kind of guy LOL. As to the Vacuum gauge they will show a lot more then just a vacuum leak. Google up a Vacuum gauge chart and take a read.
     
  18. Feb 22, 2020
    TonyM

    TonyM Member 2023 Sponsor 2022 Sponsor

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    I hooked up the timing light and tried to adjust the timing but I could not get the mark on the pulley to come anywhere close to the indicator on the engine without it stalling out. Mark on pulley is about an inch in front of engine indicator for 5° BTDC. With this in mind, I adjusted the idle screw as well as the fuel/air screw on the carburetor. I also used my stethoscope and can find no differences in engine sound no matter where I scope it. I need to do the rear Main seal at a local shop (I don’t have the capacity in my garage) so may wait on diving into valves until then.

    This is what it is sounding like now at the exhaust . Much better but still the occasional “puff puff”.

     
    Last edited: Feb 22, 2020
  19. Feb 22, 2020
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    A significantly burnt-out valve would be much more regular. Maybe it's running rich, occasionally combusting in the exhaust pipe??
     
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  20. Feb 22, 2020
    Focker

    Focker That's a terrible idea...What time? Staff Member

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    Still sounds like the idle is too high. What's the RPMs at idle?

    I'm hoping it's simple, like a dirty carb. Give the carb a good cleaning. Look at the power valve at the bottom of the carb. It's often overlooked.
     
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