1972 Dart Swinger won't start

Small Block Mopar Engine

  1. 1972trucks

    1972trucks Well-Known Member

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    I have a 72 Dart with a 318. When I got it it would not fire. I have changed the carb, voltage regulator, ballast resistor, coil, plug wires, plugs, checked the fuseable link, new points, haven't replaced the distributor as it seems to work fine. It turns over fine but just won't hit. Scratching my head . Any ideas?
     
  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    You have to learn to troubleshoot instead of "throwing parts" at the problem. I am not making fun, I'm saying that is the way it is.

    Start by (if you don't have one)

    Wander over to MyMopar and download a factory service manual.........for free. Some of them there are due to the efforts of some guys on here

    MyMopar - Mopar Forums & Information - Service Manuals

    Also at that site is other articles and literature. Sometimes easier to follow but not always as detailed are the aftermarket wiring diagrams. Usually I prefer the diagrams in the shop manuals. These aftermarket ones are always two pages you can print them out

    MyMopar - Mopar Forums & Information - Mopar Wiring Diagrams

    There's lots more info archived over there

    MyMopar - Mopar Forums & Information - MyMopar Tools/Reference

    Next, it is important to understand how Mopar starting / ignition works, the difference between using the key to crank vs jumpering the starter relay, and to attempt to determine if the problem is fuel/ carburetion, general engine condition, tuneup, or electrical problems causing poor spark
     
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    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      "Let's start"

      With ignition.

      In a Mopar, for many years, you have TWO separate contacts in the ignition switch..........."IGN 1" and "IGN 2". IGN1 is hot ONLY in the "run" position, and feeds power up to the cluster/ gauges, etc, as well as out through the bulkhead to the ignition system (to the ballast resistor and through it to the coil), to the voltage regulator IGN terminal, the blue alternator field, electric choke if used, any smog devices such as idle solenoid

      THAT IGN 1 IS NOT HOT during cranking................

      So when starting the car USING THE KEY, the IGN2 comes into play. This is (many years) a brown wire comes off the IGN2 contact on the ign switch, out through the bulkhead connector, and ends at the coil side of the ballast resistor. THAT IS the ignition power for starting, and feeds a "good hot" voltage to the coil for starting

      SO WHAT?

      What else you need? You need tune up tools, timing light dwell, but you also need a MULTIMETER, a 12V test lamp, a few alligator "clip leads" and an inline spark tester.

      "Rig" your spark tester to the coil high voltage tower to ground. "Rig" it so you can see it through the hood gap, and crank the engine USING THE KEY. You should get a nice hot spark at least 3/8" and more typically 1/2" long, a bright blue "snap." DO NOT USE the resistor coil wire for this test, use a SOLID core wire. If you "rig" your tester in "open air" you do not even need to use high voltage wire

      NEXT

      Hook your voltmeter to the coil+ Crank the engine using the key. You should have "same as battery," meaning whatever the battery reads during cranking. You need AT LEAST 10V 10.5 or higher is "better."

      POINTS

      Breaker points can be poorly adjusted, dirty, burned, greasy, and exhibit high resistance. They can be physically misaligned and make poor contact

      CONDENSER The condenser MUST BE good. There are several things that can go wrong with them, the only "good" way is to try and buy good quality brand name ones (hard nowadays) and keep the old one if it was OK. Substitute one or more if you "think" one is bad

      JUMPERING THE STARTER RELAY. Many people, including me, do this occasionally to crank the engine. Here's the situation you "set up" when you do this.........

      With the key "in run" the coil is getting voltage through the ballast. With the engine stopped, the battery barely at 12V, and through the ballast, you might have 8V at the coil.

      WHEN YOU jumper the relay to crank, that 8V goes DOWN, because now there is nothing to bypass it. You might only have 4-5V at the coil. DO NOT check spark when jumpering the relay it will give you skewed results
       
      Last edited: Nov 26, 2017
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      • Mopar Tim

        Mopar Tim FABO Gold Member FABO Gold Member

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        Are you getting any spark? And gas in the Carb, spraying in thru the accelerator pump circuit? Yes to both, run a compression test. Comp OK? Timing is suspect. Timing chain, and Dist timing. Nothing else it can be,
         
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        • 67Dart273

          67Dart273 FABO Gold Member FABO Gold Member

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          Yup................Compression, spark and fuel...............
           
        • 1972trucks

          1972trucks Well-Known Member

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          Thanks for the reply. Everything that I have changed I would normally do to car that has been sitting for a while. I am not getting a spark. I am better at bodywork than mechanicals. Can hold my own but just ok. So how do I check the IGN2
           
        • 67Dart273

          67Dart273 FABO Gold Member FABO Gold Member

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          I told you above, please re-read the post. Hook your meter to coil + Crank using the key, and read the voltage. Rig a spark tester as I said

          If you have good voltage to the coil during cranking and no spark it is time to pull the cap and examine the points. Check the setting substitute another condenser.

          See if the points are actually opening and closing. To do that put your multimeter or test light on coil NEG turn the key to "run" "Bump" the engine so the points are open and then closed. The light should go on and off as the points open/ close, or your meter should read from near zero to full battery voltage, around 12V

          You can get a "quick idea" with just a screwdriver. "Rig" a spark gap in the coil tower. "Bump" the engine so the points are closed. Turn the key to run, and use a screwdriver to open the points. Every time you open/ close the points you should get a big "snap" spark from your test gap. With a lamp or meter on coil NEG the voltage should go from no lamp......near zero voltage witih points closed, to a bright lamp........voltage same as battery.....with the points open
           
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          • 67Dart273

            67Dart273 FABO Gold Member FABO Gold Member

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            ALSO.............if you have a tach.........temporarily unhook it........

            ONLY thing that should be connected to coil NEG is the distributor wire
             
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            • 1972trucks

              1972trucks Well-Known Member

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              Thanks for the help. I am not trying to be helpless here but I need help. I am not getting power to the coil. Two questions . . . can I jump the ignition switch to start the car? Second is it appears to be the Ign2 side how do I fix that?
               
            • 67Dart273

              67Dart273 FABO Gold Member FABO Gold Member

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              You have to check it out, or have someone help you. Download a shop manual from MyMopar. Access the switch connector coming out of the column and use a meter or test light to see if you have power there. I'll have to look it up............

              IF it is IGN2 (no power when cranking, using the key) it is either the ignition switch, the switch connector, the terminal in the bulkhead connector, or someone messed with the factory wiring in the engine bay and that somehow got left "loose."

              The 72 shop manual.........
              page 8-144 is the wiring index
              page 8-145 is the layout of the bulkhead connector
              page 8-150 is the A body inst. panel wiring

              Here is a clip from page 8-151, the ignition switch........

              switch.jpg

              In the diagram, the YEL "start" wire goes from the switch out through the bulkhead and connects to one of the small "push on" terminals of your starter relay. It is hot ONLY in start

              Next, BLACK, "accessory" should be hot either in "run" or "accessory"

              Next, Dark BLue, "IGN1" is hot ONLY in run, NOT start This is what feeds power to the coil ballast, the blue alternator field, the VR IGN terminal, and a few other things depending on car model

              Next, BRown, IGN2, is hot ONLY in start. This is the one to check Must be hot with key in "start"

              Below that is RED the main power coming into the switch, hot all the time
               
              Last edited: Nov 30, 2017
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