72 dies when warm at idle

Discussion in 'Ranchero Tech Help' started by 2beast, May 30, 2011.

  1. 2beast

    2beast In Third Gear

    Messages:
    223
    Location:
    Streator, Il
    Lately have been having a bit of trouble with my 72 GT / 351 CJ.

    It starts fine and runs great.
    Drove about 30 miles this morning.

    After it is up to temp, it will die after it idles. Not immediately but after a few minutes.
    It will not start until it cools down.

    Makes me sometimes nervous at a long stop light.
    As long as I drive it (or lightly rev it), it is fine.


    I have tried insulating the fuel line in front of the engine and replaced the fuel pump along with some other adjustments.

    Any ideas?
    thanks,

    Greg
     
  2. ribald1

    ribald1 Banned PLATINUM MEMBER

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    19,727
    Location:
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    Might be a bit of vapor lock. Make sure the fuel lines are not touching, or near touching the hot parts. That includes the incoming line running by the header.
     
  3. burninbush

    burninbush In Maximum Overdrive

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    After it is up to temp, it will die after it idles. Not immediately but after a few minutes.
    It will not start until it cools down. >2beast

    ++++++++++++

    I wonder if maybe it is gradually flooding itself, from a float set too high, or a leaky float needle? You said 'won't start until it cools down' -- guessing you mean won't restart ... like, until how many minutes after?

    Will it also die like that just sitting in your driveway idling? [from a cold start, after the choke is open and it's off the fast-idle cam]

    Do you have a tach? What is your warm idle rpm? Would it make any difference to shift it into neutral at stops?

    Is it possible this is old gasoline? Have you tried a different brand?

    If it is actually boiling the gasoline in the carb, it could be useful to put a 1" phenolic spacer under the carb.

    Maybe your coil goes weak when it gets hot?
     
  4. 210eddiep

    210eddiep In Overdrive

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    711
    Location:
    boerne, texas
    happened to my 71 not long ago. it was the condenser in the distributor.
     
  5. 2beast

    2beast In Third Gear

    Messages:
    223
    Location:
    Streator, Il
    To answer a few questions.......

    I was thinking vapor lock so I did wrap the fuel lines up from the fuel pump up to the carb.

    The fuel is fresh.
    It will idle around 700-750 RPM sitting in the drive after the choke opens with no problem. Actually did for better than 20 minutes when I changed the fuel pump the other day.

    4 speed so it is in neutral.

    Sometimes takes nearly an hour before it wants to start again.

    It actually seems like when it happens it is starving for fuel.
    that is why I changed the fuel pump.

    The idea of a spacer under the carb sounds plausible.
    I will check into that as well as some of the electrical suggestions.

    Thanks for these and any other ideas :)

    Greg
     
  6. scrnic1

    scrnic1 In Fourth Gear

    Messages:
    274
    Im thinkin ignition considering the long cool down required. What ignition system is in a 72'? I had a bad magnetic pickup in my75', did the same damn thing. If it was flooded, you could always clear a flood by holding your foot to the floor and cranking it for about 15 seconds. That usually clears it out. Still think electrical though given it can take up to an hour. I dont know what your climate is like where you are, but ive never ever had a vapor lock situation up here in WA, even in 100 degree weather with an overheating engine. Good luck
     
  7. paparoscoe

    paparoscoe In Overdrive

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    SoCal
    I was thinking along similar lines. I have had a coil do that to me, but it wasn't tied to a prolonged idle. That part has me scratching my head. Vapor lock is plausible. Is your choke working correctly?
     
  8. ribald1

    ribald1 Banned PLATINUM MEMBER

    Messages:
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    Location:
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    When it dies, take the air cleaner off and open the throttle while looking into the carb. If there is no squirt of gas, you have vapor lock. If there is gas, you may have an electrical problem.
    If it is vapor lock, look at the line from the fuel pump to the tank. It should be well clear of the exhaust all the way. Sometimes changing a pump can pull the line so it ends up in a hot spot.
     
  9. 2beast

    2beast In Third Gear

    Messages:
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    Location:
    Streator, Il
    The choke is functioning fine.

    You guys have given me some other good ideas of what to check.

    Thanks, I will let you know what I find.

    Greg
     
  10. ClskMstg

    ClskMstg In Fourth Gear

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    Location:
    Dickson, TN
    That happened to me with my 67 mustang with a 390 once - the points were adjusted too close I think it was. It was a point issue for sure.

    I'd check distributor area first - then, check idle air adjustment at the carb
     
  11. 2beast

    2beast In Third Gear

    Messages:
    223
    Location:
    Streator, Il
    I took it out for a drive today and it drove fine.

    After returning home I let it idle on the drive.
    It took less than five minutes to die and would not start.
    I did check the carb and it did squirt gas when I worked the linkage.

    So it looks like I will be persuing the electrical solution route.


    Thanks for the ideas.

    Greg
     
  12. CLessley

    CLessley In Third Gear

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    Location:
    Fresno, CA
    I've had a similar problem in both my cars. Though car is garaged right now, I remember dreading that lonely stoplight situation.
     
  13. inenidok

    inenidok In Overdrive

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    enid OK
    check your coil my chero would do that and it was the coil breaking down when i got warm. and would restart when i got cold,
     
  14. Fomoco8

    Fomoco8 In Maximum Overdrive

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    Have you converted it to a Duraspark Electronic System?....a control box will do that also
     
  15. 2beast

    2beast In Third Gear

    Messages:
    223
    Location:
    Streator, Il
    I think I found it.
    I changed the condenser in the distributor and it appears to have taken care of the problem.

    It was really cool out today so I will check it again in a couple of days as the temps climb.

    Thanks for the help!

    Greg
     
  16. paparoscoe

    paparoscoe In Overdrive

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