Backfiring and or shutting off Help!!

Discussion in 'General IH Tech' started by Ezlydistracted, May 23, 2020.


  1. Ezlydistracted

    Ezlydistracted Farmall Cub

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    So I have a 78 international Scout with 345 in it. About a year ago at highway speeds it would randomly lose power and then backfire. Then would run fine and not do it again. Lately it has been happening almost every time I drive it. I replaced the coil, fuel pump and both fuel filters. What should I start to look for? Please help
     
  2. jeff campbell

    jeff campbell Lives in an IH Dealership

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    Go the whole route. Cap , plugs , rotor , wires. NEW magnetic pickup would be 1st thing if all others are in good shape.
     
  3. Ezlydistracted

    Ezlydistracted Farmall Cub

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    Ok will do thanks . Now do I replace the distributor, rebuild it or do the duraspark upgrade? Trying to figure out what’s the best thing to do in the long run.
     
  4. Ezlydistracted

    Ezlydistracted Farmall Cub

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    Oh to add some more info it is a prestolite electronic distributor
     
  5. Ron A

    Ron A High Wheeler

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    Verify fuel supply. I know you changed the pumps, but it might be leaning out and running out of fuel.It would be best to run a fuel pressure gauge and find out what is going on. It could be as simple as a gas cap not letting air into the system or a plugged sock filter inside the gas tank. Pinched fuel line. If fuel pressure is good while this is happening, then you know you can eliminate it as a cause.
    Here is some info on the duraspark http://www.binderplanet.com/forums/index.php?threads/duraspark-conversion.110510/ Note that you need a holley distributor, not a prestolite.
    IMO upgrades can be really good, but not if you think it will miraculously fix an un diagnosed problem. Best to diagnose a problem first, then upgrade for the sake of having a better system.
     
  6. RinTX

    RinTX High Wheeler

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    I agree with Ron. The best approach is to troubleshoot and fix what is currently wrong before you start changing/upgrading. One thing at a time otherwise you might get to a position where you can not make it run and have no idea which change you made is the cause
     
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  7. Ezlydistracted

    Ezlydistracted Farmall Cub

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    Ok thanks that’s good advice. I do need to replace my fuel sender as it only goes to half full when filled. So there is an internal sock filter in the tank? I think I will start there
     
  8. Ron A

    Ron A High Wheeler

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    There is, or was a sock filter in tank from the factory. I had to blow air back down the line to clear one out on the road one time. That gauge issue might not be the sender. Common issue with Scouts is the Constant Voltage Regulator CVR under the dash. Here is one thread, out of many, that might help. http://www.binderplanet.com/forums/index.php?threads/cvr-rebuild.116212/
     
  9. Ezlydistracted

    Ezlydistracted Farmall Cub

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    Wouldn’t the cvr cause all the gauges to act up?
     
  10. Kyle Dillehay

    Kyle Dillehay Farmall Cub

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    I'm dealing with the same problem, no solutions yet, have been told that old / bad gas might cause backfiring as well.
     
  11. winchested

    winchested Y-Block King

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    Have you checked the timing? Bad timing causes backfiring.

    Have you pulled the carb apart and cleaned it?
     
  12. mallen

    mallen Y-Block King

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    D
    Do not replace the distributor with a parts store rebuild. They are junk. If it needs to be rebuilt, have your original rebuilt. But first, figure out if it does. Put a dial gauge against the shaft and push the shaft to see if it moves side to side. Then crank the motor and see if there is run out. Do this in two directions perpendicular to each other. Then put it back together. Connect a tachometer and a timing light. Disconnect the vacuum advance and plug the hose. Run the engine at various rpms and compare the timing advance to the listed specs.m. Then connect a mightyvac to the vacuum advance can and check the advance at various vacuum levels. Compare to listed specs. If that all passes, a rebuild is a waste of money. Doesn't your distributor have an integrated module? That could be the issue. Might be failing hot. Not sure how much a new one costs. If its cheap, it might be worth replacing, but not if its like 100 bucks, you want to be sure before dropping a lot of money. There's also things like a pertronix but Thats in the 100 bucks range, plus it takes some level of modification to install, so you need to be sure before going there or you will cause even more headaches.

    You engine acts like mine did when I was having trouble with the points. But it also acted like that when I had carb troubles and the floats were sticking causing it to randomly flood, the not.
     
    Last edited: May 26, 2020
  13. Ezlydistracted

    Ezlydistracted Farmall Cub

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    Ok but I do not have points. My carb is only 2 years old but I will have to check it out. Thanks
     
  14. mallen

    mallen Y-Block King

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    You dont have points, but all the points are is a switch that closes the coil primary circuit to charge the ignition coil then opens it creating a spark, when the distributor is aligned to certain positions in time with the cam shaft. You do in fact have such a switch in your vehicle. Its just electronic. A malfunction in that system will cause the exact same symptoms.
     
  15. Ezlydistracted

    Ezlydistracted Farmall Cub

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    Ok sorry I understand. I will try these this weekend and report back. Thanks for your help
     
  16. tahoescout

    tahoescout Farmall Cub

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    Mine did the exact same thing and it was the electronic ignition module which is in the prestolite distributor. its simple to replace or you can upgrade to pertronix. I keep a spare unit in my glove box just in case.
     
  17. Ezlydistracted

    Ezlydistracted Farmall Cub

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    So I had an extra electronic prestolite distributor. I switched it out and that has solved the problem. Thanks for everyone’s help. Love the binder community
     
    Erik VanRenselaar likes this.

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