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Thread: mechanics cant figure out whats wrong w my 79 scout

  1. #1
    Join Date
    Apr 2011
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    Dallas
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    Default mechanics cant figure out whats wrong w my 79 scout

    So here's the deal, I recently bought my Scout back in April and all of the sudden I am running into an issue with it dying. Ill drive it for an hour and then it starts to pulse when I hit the gas and eventually die when the RPMs get low. My local mechanic tinkered with the exhaust and said they fixed it but they didn't. Within a few days it was doing the same thing again. I took it back in and they cant figure out whats wrong with it. At first, they said it's either a gas or spark issue. Then they thought it might be a problem with vapors building up so they put in a new fuel pump and filter, dropped the tank fixed some crushed vent tubes and blew out all the fuel lines. They thought they fixed it again, but it's still doing the same thing. Since they cant hook it up to the computer, they are obviously inexperienced and need help. Im currently searching for a IH experienced mechanic in the dallas area, but I need the scout fixed sooner then later. I have to pay these guys, so I would like for them to fix it instead of taking it somewhere else and starting the familiarization process all over again. Any ideas of what might be wrong? Or if anyone has had a similar problem. Or knows a good Dallas mechanic. Any help would be appreciated!

  2. #2
    Join Date
    Dec 2009
    Location
    Nebraska
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    128

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    Can you describe what you have for an ignition system? First thought that comes to my mind is the coil is overheating.

    Ron
    Ron Mc
    1975 Scout II
    1974 Scout II
    1965 IH pickup----sold it

  3. #3
    Join Date
    Apr 2011
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    Dallas
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    Well he just cleaned out the carburetor and got it running, but odds are it won't work. He has checked the coil, tells me its not that. I wish I new more about it. But with this summer of 50+ 100 degree days, im sure it has to do with the heat.

  4. #4
    Join Date
    Feb 2009
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    Minot, ND
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    Your symptoms are classic of two different things. The first is fuel starvation. This is caused by (in no particular order):
    A pinched fuel line. The fuel line runs under the body and can get pinched when the body mounts sag.
    Vapor lock. This is caused by air in the fuel lines on a warm day. The gas fumes in the air expand greatly with heat. When the fuel bowl fills with air, it pushes back against the fuel pressure and you get sputtering.
    Clogged fuel line, inside or outside of the tank.
    Fuel pump problems. Clogged or weak fuel pump causes these symptoms as well.

    A see-through fuel filter in between the fuel pump and the carb will tell you a great deal. Bubbles in filter=bad. No gas in filter=bad. Full filter=good. If you also have a filter before the fuel pump, you will know what the problem is pretty fast.

    The second reason is poor spark. The 79 has an electronic (prestolite) distributor. If there is a poor power feed, you can get these symptoms. If the mechanical advance or the module or something is loose inside the distributor, it could happen. Also, if your vacuum advance line has a crack in it, you can get surging due to rapid timing changes.

    Chances are this is not your coil unless it's from a loose wire or bad connection. Check the bulkhead connectors just to be sure. They tend to cause problems.
    Last edited by Allan E.; 08-31-2011 at 09:52 AM.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  5. #5
    Join Date
    Feb 2011
    Location
    Wickenburg, AZ
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    Quote Originally Posted by mr.c View Post
    My local mechanic tinkered with the exhaust and said they fixed it but they didn't.

    Any ideas of what might be wrong?
    From the first statement quoted, if true, I'd say it's wrong to let that guy work on your Scout.

    Can you confirm the ignition system is the OEM equipment?

  6. #6
    Join Date
    Aug 2010
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    15

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    Sorry guys, new member trying to reach 15-post PM threshhold...

  7. #7
    Join Date
    May 2010
    Location
    Apple Valley Ca.
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    It's actually quite simple, the Scout must die while the fuel presure and ignition circuit is being monitored. it sounds to me like the problem is just intermittent enough to make a mechanic think He fixed it no matter what is done. Electronic ignitions are notorious for failing when hot and returning to normal after a cool down period. One option is to get an old point distributor and substitue it, then a different coil but to avoid chasing You're tail do one thing at a time. Vapor lock and a relativly large rust chunk in the fuel line will do the same thing but to a sharp mechanic the way it dies will point to fuel or spark. A rust chunk will need a restriction to cause a problem such as a fitting or cuve. A Dodge van that ruind the lives of several mechanics had a collapsed inner layer of a fuel hose that would sometimes work like a check valve. The final and rarest possibility is running out of valve lash due to gutterd exhaust valves or dished intake valves, This is usually the result of incompetent machine work on the cylender head or prolonged running with a lean mixture and incredibly rare. This condition can be checked by compressing the lifter at TDC copression stroke, there should be at least .030" clearance between the valve and rocker arm. Feel free to print this and show it to You're mechanic if You are'nt doing it You'reself.
    Last edited by smogdredd; 09-04-2011 at 04:15 AM.

  8. #8
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    Dec 2009
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    Page AZ
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    Quote Originally Posted by smogdredd View Post
    Electronic ignitions are notorious for failing when hot and returning to normal after a cool down period.

    The final and rarest possibility is running out of valve lash due to gutterd exhaust valves or dished intake valves, This is usually the result of incompetent machine work on the cylender head or prolonged running with a lean mixture and incredibly rare. This condition can be checked by compressing the lifter at TDC copression stroke, there should be at least .030" clearance between the valve and rocker arm. Feel free to print this and show it to You're mechanic if You are'nt doing it You'reself.
    CORRECT: But all that is required is to check whether there is spark right after it quits. This is so rare that in 50+ years of being a mechanic I have never seen it as stated with hydraulic lifters. How do you compress a working hydraulic lifter in a reasonable time? Also the purpose of hydraulic lifters is to eliminate the valve lash.Also how does the machine work apply when he says nothing about the engine being worked on?? Also if this problem shows up on a engine with solid lifters(old IH) it will usually only cause low compression and/or a miss, not the above problems. Quick reply would still be carb in some way if there is spark when the engine quits.
    73 1210 4x4 Travelette 5 spd. 392
    300 utility tractor
    64 Scout 80-152/ weber 32/36
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    73 Scout2, 304.4 spd. runs almost rust free!
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  9. #9
    Join Date
    Jan 2012
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    13

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    How do you compress a working hydraulic lifter in a reasonable time?
    valves recessed in head, engine heats up, valve stems get longer, hydraulic gets to bottom of plunger, valves can no longer shut.

    but that is not very likely.

    I would be thinking fuel pump, How about trying a 5 gallon fuel can, put the hose in it and see if it keeps running to eliminate tank. If you have a carb and mechanical pump and fuel does not continuously flow back into tank this will work.

  10. #10
    Join Date
    Jan 2012
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    2

    Default

    just went threw a simialor situation it was the elictronics inside the distributor

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