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Starting Issues

Discussion in 'Early CJ5 and CJ6 Tech' started by heffleysmill, Jun 29, 2011.

  1. Jun 29, 2011
    heffleysmill

    heffleysmill 7 Slot Hotshot

    Columbus,TX
    Joined:
    Jun 4, 2010
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    152
    Here is a general overview of my situation,
    Freshly professionally built 134,
    new carb that has been bolted to an old engine for about five years but had only been run two or three times(so the housing and pivot points are not wore out)
    new plugs, wires, coil, electronic ignition, fuel pump and filter
    the problem that i have started to experience more often now that the new carb is on( but it did happen prior on occasion)
    sitting overnight you can turn the key not needing to pump throttle fires up and never misses a beat, runs perfect, for hours it will run great, but........
    as soon as you shut it off, it doesn't matter if it had been running for two minutes or two hours, i can crank and crank, no throttle, half trottle, flooring it or pumping it, nothing
    it will absolutly not start, you can crank till the battery is dead.
    now the strange thing is, I can put my son or wife behind the wheel while I push, and whith the slightest amount of momentum, pop the clutch, boom fires right up with ease!

    Does this sound like vapor lock? and if so, why does it push start with such ease?

    Suggestions,
     
  2. Jun 29, 2011
    duffer

    duffer Rodent Power

    Bozeman, MT
    Joined:
    Sep 17, 2009
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    Certainly would appear to be a fuel issue. Are you getting a shot from the accelerator pump when it will not start? I would also try giving it a squirt of gas in the carb while cranking (I keep a Nalgene squirt bottle for this-something that will not dissolve). If not, vapor lock is a distinct possibility and I would be looking at the usual suspects, including checking the pressure on the new pump, potential obstructions in tank pickup, and fuel lines.
     
  3. Jun 29, 2011
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    cordele, Ga.
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    Don't know how your elect ignition is wired but sounds like it is not getting power in the crank condition. The ignition switch will not provide ignition power in the crank position. There has to be a by-pass circuit available. I believe this circuit is the problem. A test light will show this real quick.
     
  4. Jun 29, 2011
    heffleysmill

    heffleysmill 7 Slot Hotshot

    Columbus,TX
    Joined:
    Jun 4, 2010
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    I have checked with a spark tester and I do have spark in the cranking position, would a spacer between tha carb and intake help ( is the such an animal out there or would one have to be made)
    I also have out of the fuel pump to carb, a copper fuel line with about 5 to 6 " of space from the exhaust manifold, should this be rubber or maybe stainless?

    What or are there any high quality aftermarket carbs on the market?
     
  5. Jun 29, 2011
    duffer

    duffer Rodent Power

    Bozeman, MT
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    But wouldn't that affect starting when either cold or hot-unless there is some solid state component crapping out when it gets warm?
     
  6. Jun 29, 2011
    heffleysmill

    heffleysmill 7 Slot Hotshot

    Columbus,TX
    Joined:
    Jun 4, 2010
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    Just installed new pick-up module about a week ago no change for the better or worse!
     
  7. Jun 29, 2011
    SIDSCJ

    SIDSCJ Jeep addict

    14th State
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    If it was vapor lock, it shouldn't start so quickly when pushed. Next time it does it, pull the gas line off the carb and have someone crank it and see if you're getting fuel to the carb. If so, my money is on a wiring issue in the start circuit. Foot starter or solenoid off the key switch? Unless you've run the fuel line clamped to the exhaust (NOT), there's no way it should vapor lock in 2 mins run time.
     
  8. Jun 29, 2011
    heffleysmill

    heffleysmill 7 Slot Hotshot

    Columbus,TX
    Joined:
    Jun 4, 2010
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    I just wonder if it would be a wiring issue, why will it start so easily when it has sat for ten or twelve hours, the engine may turn over once or twice then fire off, no hesitations.

    Would timing maybe a factor? it runs smooth, but I can vary the timing about 5 degrees befor I get any major noticable change in idle.
     
  9. Jun 29, 2011
    bobo

    bobo Sponsor

    canby or
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    It doest seem to be a fuel problem, it runs perfect shut it off, bump start and it runs perfect again. Starts cold when coil is cool wont stat when hot, coil is now hot ,crank with starter which draw lots of amp, weakens ignition voltage= no start. Bump start= full voltage to coil. You could try a jump wire 12ga from batt to coil to test this
     
  10. Jun 29, 2011
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    cordele, Ga.
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    When copper heats up it grows. This can break a connection and when cools down it will re-make contact. The key info here is that even when hot it will start with a light push of the car. This condition puts full battery voltage to the ignition and you are not using the starter which has the ign by-pass circuitry which is normally thru the solenoid or a relay of sorts.
     
  11. Jun 29, 2011
    PeteL

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

    Hills of NH
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    Does sound to me a lot like a weak spark (ignition coil), based on your ability to bump start it.

    I've had have several older vehicles that won't start when hot, but can be fired right up by bypassing their in line resistor and getting full voltage - or with an easy bump start or hand crank while there is no voltage drop from cranking the starter.

    Possibly your starter has a poor connection or bad ground, and is drawing down the voltage even more. (I just had to remount the starter on an F-head in order to refresh the grounding.)
     
    Last edited: Jun 29, 2011
  12. Jun 29, 2011
    jackfunkhouser

    jackfunkhouser New Member

    Mico, Texas
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    I would check the electrical connections. Maybe as a test, connect the positive side of the coil right to the battery. See if you can get it to start that way. If it runs then you know you have a poor connection.
     
  13. Jun 30, 2011
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Another remote possibility is the ignition switch. They can fail and cut off power to the coil while cranking.
     
  14. Jun 30, 2011
    heffleysmill

    heffleysmill 7 Slot Hotshot

    Columbus,TX
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    ok update time, Hooked a jumper direct from bat to the coil, bam! fires right up,
    thanks guys!
    NOW, what would cause this all of a sudden, the coil is maybe two months old, ignition switch maybe three years old,
    I know parts fail, especially electrical....
    Happy I know what is wrong, still puzzled from the source!
     
  15. Jun 30, 2011
    SIDSCJ

    SIDSCJ Jeep addict

    14th State
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    Check voltage coming in to the coil.
    I have a newer Napa coil, stated "no external resistor required".
    Batt voltage coming in is 14.5 or so when Delco alt is charging. coil will get quite hot, so I put a ballast resistor in.
    Much better now.
    Pull your jumper wire and wait for symptom to reappear. Check voltage and find out where the culprit is.
     
  16. Jun 30, 2011
    PeteL

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

    Hills of NH
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    "Hooked a jumper direct from bat to the coil, bam! fires right up,...NOW, what would cause this all of a sudden"

    As per my earlier suggestion, you may be by-passing an external voltage-dropping resistor, or some poor connections that are creating resistance in the coil circuit. Or perhaps you have a dying coil that is weak when hot.

    It bump starts because without the starter drawing on the battery, voltage is adequate.
     
    Last edited: Jun 30, 2011
  17. Jun 30, 2011
    jackfunkhouser

    jackfunkhouser New Member

    Mico, Texas
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    You are looking for a poor connection. The wire at the coil. Two wires at the ignition switch and and although I have looked at the diagram in awhile maybe two wires at the head light switch. Possible the ignition switch is bad.
     
  18. Jun 30, 2011
    jackfunkhouser

    jackfunkhouser New Member

    Mico, Texas
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    We are in Comfort Texas on vacation and I'm living Internet hell. Use a good 12v source to back track through your wiring to find the bad connection. I hope that makes sense.
     
  19. Jun 30, 2011
    jackfunkhouser

    jackfunkhouser New Member

    Mico, Texas
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    It's not the coil. Otherwise I would not have work when you hooked it up directly to the battery.
     
  20. Jun 30, 2011
    madgician

    madgician New Member

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    try a differant points condenser . condenser gets hot and then loses ground then cools off and regrounds its self.
     
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