Diagnosing Distributor - No Spark Chase

Discussion in 'Electrical and Ignition' started by perko, Aug 13, 2018.

  1. perko

    perko Well-Known Member

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    Hey everyone, I'm chasing a no spark problem and I could use a little advice.

    1973 duster with a 67 318.
    Factory electronic ignition.

    I was moving it a few days ago to make way for my tenet's project and it kept dying when I reved it. I could re-start it and idle down the alley but that was about it. Then, nothing. Now its got no spark (tested with an inline spark tester). I've got power at the positive terminal of the ignition coil and after bench testing the coil I don't think that is the problem. It seems like the next gizmo down stream is the distributor. Is there a good way to diagnose a distributor in this application? I didn't see any obvious signs of damage to the rotor or cap.
    Thanks,
    -Alex
     
  2. TrailBeast

    TrailBeast Slightly Twisted Member

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    Don't know the exact ohm rating for those but I'd bet Google does.

    If you connect a volt meter set at it's lowest AC volts to the two wires and spin the distributor you should see a big variance around the 1 volt reading.
    It's not real accurate but it does tell you if the pickup coil is sending a signal for the ignition box.

    The distributor pigtail on the harness side when disconnected from the distributor exposes 1 of the metal contacts of the two prong plug.
    Touch the exposed pin to ground with your key on and you should get 1 spark per touch to ground.
    This tells you the box is probably ok.

    Before any of this though I would check the pickup coil gap for approx. .008
    They can act like that if the gap gets too big.
     
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    • '63GT

      '63GT Well-Known Member

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      There are a lot of cheap imported pick-up coils on the market. and they fail A LOT.
      If the orange (actually closer to amber on these parts) wire on your pick-up assembly says, 'chang', or ' dianlan', you've got an import. Standard Motor Parts still offer a domestic made pick-up. NAPA too, I think.
      Also too, pull the phillips retaining screw out of the center of the connector to the control box, and with the key on, disconnect and reconnect it. Sometimes this is enough to 'wake up' the box and get you running. if not, it's most likely the pick-up.

      Of coarse, this is pending a good Ignition sw, connections, etc..
       
    • 67Dart273

      67Dart273 Well-Known Member

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      Some general BS:



      Here's a post I made about the simplest way I know to get across testing the ECU/ ignition parts

      74 duster electrical problems


      You need a coil, the ECU and the distributor

      Lay it out on the bench. Follow the diagram. Find the two distributor pickup terminals on the ECU. Hook them to the distributor

      Hook the ECU case to battery NEG

      Coil does NOT need grounded

      Distributor does NOT need grounded.

      Hook coil + to the power lead terminal on the ECU. Get a clip lead hooked there and let dangle. This is your battery "hot" when you are ready

      Hook something from coil "case" to a probe for testing spark.

      Hook up your power clip lead. Twist the distributor shaft while holding the test probe near the coil tower. The thing should make sparks

      If not, unhook distributor. Take first one, then the other pickup clip leads, and "tap tap" ground them at the battery connection. Coil should make 1 spark each time you do so.

      If not, try another coil. If that does not fix it replace the ECU

      IF you hook it all up and it WORKS, then there is something AFU in the car harness. SUSPECT a bad ECU connector OR a bad DISTRIBUTOR connector
      =============================================
      This is all you need to test the basics of the ignition. You can easily test the ballast separate. A battery, the ECU, distributor and a coil, and of course some test leads

      NOTICE!! The following are not individual tests!!! They are showing how the system connects. Read carefully

      2ai0wsj.jpg

      Below, the basic diagram for a 4 pin ECU

      166lmj7.jpg

      Below, the wire for testing spark. I use my 12V test light. No, LOL the spark won't blow up the bulb

      166lmj7.jpg

      Below, the ground connection. ALL you need is one wire from batt NEG to the ECU case

      xawjl.jpg

      Below, the two distributor connections. In the car these are polarity sensitive, but for testing does not matter

      b3opvm.jpg

      Below, the coil NEG connection

      6jfywp.jpg

      Below, battery PLUS connection, one wire to this terminal of ECU and jumpered over to + side of coil


      11lqu5l.jpg

      Below, all hooked up and ready to test (except for battery ground). Should produce sparks at least 3/8" and typically 1/2" long

      1zzoya0.jpg

      Below, distributor "one wire" test. I have removed the other distributor wire for simplicity. Take the bare connector end or this clip lead (the yellow) and with everything hooked up, ground it repeatedly. Each grounding should result in a spark (In this photo you need to hook up the ECU ground wire, I left it off for the photo)

      vgitld.jpg
       
      Last edited: Aug 13, 2018
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      • 67Dart273

        67Dart273 Well-Known Member

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        Make sure you have power to coil + WHEN CRANKING

        Measure power to coil + both with key in "run" and in "crank"

        With power in "run" disconnect distributor connector. Take the engine harness end of the connector, and tap the exposed terminal onto ground. Each time should produce a "snap!" spark at the coil

        Remove/ and work all connectors in/ out several times to scrub the terminals and "fell" for tightness, ESPECIALLY the distributor. Examine them with a flashlight for corrosion

        Remove cap, inspect for dirt/ water in cap, rotor "punch through." Inspect the reluctor/ pickup for damage, rust, debri, and shaft wiggle. Set the gap I've forgotten, .008" I think. INCHES, not mm. Make certain the reluctor and pickup don't touch. TB above already posted checking for AC voltage

        MAKE ABSOTLUTELY CERTAIN that the ECU is grounded!!!

        Measure coil + voltage with key in run........should be no less than say, 6V and no more than, say, 10V. Measure coil NEG it should be quite low, say, 1-3V or so. If you have a tach DISCONNECT THE tach wire for testing. The tach may be shorted
         
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        • perko

          perko Well-Known Member

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          Do you think that I could spin the distributor by bumping the engine over when I'm testing the two wires with the volt meter? I hate trying to take the hold down off.
           
        • perko

          perko Well-Known Member

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          Damn 67dart273. Bad ass. Thanks
           
        • '63GT

          '63GT Well-Known Member

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          Holy Moly 67Dartman273 !! lol too much coffee? You're awesome :)
           
        • CCHHAARRGGER!

          CCHHAARRGGER! Well-Known Member

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          Its either the ignition box , or the ballast resistor. Or at least I would start with these. When I use the mopar electronic boxes, I always carry a spare as with the ballast resistor. Had to many go out over the years. So First check the ignition box, go but a cheap one first to see if it solved the problem. If neither of these work and you still have no spark then I would try a distributor. However I have only had one magnetic pick up go bad in 30 plus years of messing with mopar distributors ( maybe i have been lucky)
           
        • 67Dart273

          67Dart273 Well-Known Member

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          ^^I don't know why you would say that, it could be several things......Several members on here had them quit BECAUSE THE ECU became ungrounded......loose rusty bolts...........
           
        • '63GT

          '63GT Well-Known Member

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          Don't misunderstand, I'm impressed with your willingness to help to the degree you did :)
          Well done !!
           
        • CCHHAARRGGER!

          CCHHAARRGGER! Well-Known Member

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          I am sorry to have offended the master of this forum....again
           
        • '63GT

          '63GT Well-Known Member

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          I'm sorry... did I get in the way?
           
        • TrailBeast

          TrailBeast Slightly Twisted Member

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          Sure.
          Del and I have different methods of diagnosing, as you probably have noticed.
          My ways are side of the road type quick and dirty, and his are more in depth with more precise information. :D

          I always suggest a person do the quick and dirty first, and then the more in depth if the problem isn't yet found.
           
        • 67Dart273

          67Dart273 Well-Known Member

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          No, I just don't understand why you would start out by guessing the most expensive parts rather than attempting to actually find the problem. Bear in mind I've done that myself WHEN I had the parts lying around. So you don't need to get your panties all bunched up.

          Ya know recently we had a member.........the green field wire was shorted to ground in the harness. Imagine that!!! .25 worth of wire caused a problem that could have been a regulator or bad alternator!!

          As I pointed out, as simple as the ECU ungrounded. That has happened here on this very board more than once, just a simple problem with rust/ loose bolts or the OP had not thought it needed mounted to test it.

          The other problem with "throwing parts at a problem" is what if YOU DO HAVE a wiring problem? Let's say EG the connector for the distributor is broken inside.........You could change every part in the ignition...........several times.......and the thing would never run...........
           
        • AJ/FormS

          AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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          Or as happened to me, a wrong polarity on the pic-up. Starts and idles but breaks up almost as soon as you start reving it.
           
        • perko

          perko Well-Known Member

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        • TrailBeast

          TrailBeast Slightly Twisted Member

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          You got it, so it sounds like you either have a bad ECU or a ground problem on it.
          Those HAVE to be well grounded to work.

          They can also shock you a but if they are not grounded and you touch the box, so I can tell you a great and fast way to find out if it's ground problem with the box but you may not want to do it.

          Get your thumb and forefinger on both hands wet and grab the battery negative with one hand and the box with the other with the key in the run position. :D

          If the box has to get it's ground through you instead of the body metal you'll get nice little jolt.
          Yea, you wont want to do that I'll bet, but it sure does point out a bad ground quick.:D
          I just lick my fingers a little and do it.

          Maybe consider running a ground wire to the box with a bolt and nut if the metal it's bolted to looks too bad.
           
        • perko

          perko Well-Known Member

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          well the battery is dead now, so i need to steal my bosses battery tender tomorrow. I did replace the ECU with an old one i have (I got drunk one night and decided I absolutely had to had have a mopar orange box). Still no spark out of the pig tail. I did notice that the ECU is held on by two different sized bolts, both of which will not tighten very well as the sheet metal they thread into appears to be pretty wallowed out. I think that someone replaced the original bolt with a bigger one when they stripped the stock one. does anyone now of a better way to ground this thing? Seems like there should be.
           
        • perko

          perko Well-Known Member

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          I was thinking two ring terminals and some copper wire to a dedicated ground?
           
        • 67Dart273

          67Dart273 Well-Known Member

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          ^^That's ok but you need something to tighten them TO. Unrelated, it never hurts to improve block--to-body--to battery grounding. The block is usually pretty well connected to the battery through the main cable. What I like is to buy a short "starter" cable (eyelet to eylet a bout a foot--foot and a half long) and bolt to one of the rear holes on the driver side head, and then to the firewall with either a good bolt and nut (and star washers) or bolt to the master cylinder mounting stud.
           
        • 67dodgedartconv

          67dodgedartconv Well-Known Member

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          I had an ignition problem a few weeks ago. Pertronix ignition conversion. New engine, fired up immediately, ran well. 10 minutes later during cam break in at 2000 rpm, engine slowly decreased rpms, then died. Had good spark at coil, none at plugs. Had new neg batt cable with clean, tight battery and block connections. Turned out to be bad firewall to block ground wire. Connections were clean and tight but wire itself was bad, although it checked good for continuity.
           
        • perko

          perko Well-Known Member

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          well, the ECU is well grounded now. Still no spark and still no snap from the pig tail. I'm pretty sure that the ECU is good because its only got like 1000 miles on it and i tried the another one thats been sitting around for a few years. cant be 100% sure though.

          IDEA: If I put a jumper wire on the pin of the ECU associate with the sparky part of the pigtail should i expect a spark if everything is good? I'm worried there's a break in a wire somewhere.
           
        • RUSTER1971

          RUSTER1971 New Member

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          be sure the rotor is turning then try
          a new ballast resistor. I had a ballast do the same thing on an old 73 challenger 318
           
        • 67Dart273

          67Dart273 Well-Known Member

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          This in part is why I posted the procedure (photos) I would either scare up a spare scrap harness/ connector (scrap yard, etc) or scare up some jumper / clip leads. You can buy them from Mouser electronics or egag, and hook the thing up as illustrated. You could very well have a harness problem. FRANKLY the harness connector itself for the distributor is quite troublesome...........because there is little to no current..........the slightest looseness there can lose connection

          You have a spare coil you know works? Does not have to be an exact replacement.........