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    Intermittent Ignition cut-out

    Hi Guys,

    since half a year now I've been chasing an intermittent problem whose occurrence is so seldom that I can't do a reasonable fault search. Happens about once a month - the ignition just cuts out for a split second, then picks up immediately again and runs without problems for another few weeks. Twice it actually cut out 3 or 4 times sequentially giving the kangaroo petrol effect.

    I'd fitted a Powerspark Electronic ignition from LD (at the time it was "the best on the market", now Peter doesn't sell them anymore).

    - When the cut out occurs I'm pretty sure the entire engine loses the spark immediately - it's not a case of rough running.
    - The Rev Counter drops to zero and bounces straight up again.
    - It happens when accelerating or when cruising at constant speed - up to now it's not cut out during general driving around country roads.

    A few months ago after an incident I took off the distributor cap and there was a lot of black dust in there. I noticed that the black rotor had been rubbing on the spark module. Cleaned everything out and all was ok for a few months.

    As a precaution, I bought another Powerspark - and decided to re-read the instructions. There should be a real gap between the rotor and module (1 - 2mm or so) which mine didn't have. The whole set up has no oval holes for adjustment, so I removed it, filed oval holes, and managed to eek out about 0,5mm gap. (Coincidentally, I just read a day or two ago a chap who alos couldn't adjust the Powerspark to get a gap to the rotor). During the refitting I dropped a small spring washer attaching the Powerspark plate to the distributor so tightened up the screw and made a note to fit a washer when I was back home. Car ran beautifully for a week, and I'll swear it was smoother and better pulling away.

    I just replaced the washer and the flippin fault is back - it almost left me stranded on a run into town - so many intermittent cut outs I thought I might not make it back.

    I've tried to provoke the fail by pulling and shaking all wires, dizzy cap etc., but to no avail.

    Anyone else had a similar experience?

    Cheers

    Drew
    The answer isn't 42, it's 1/137

    #2
    Drew.
    It is clearly an LT problem.
    1. Have you checked the +ve lead to the coil at the end where the Lucar connector is fitted? I have seen instances where the wire was almost broken inside the insulation..
    2. Is the wire that earths the distributor base plate to the body secure?
    3. Could it be a fault with the ignition switch?
    Mike.

    Comment


      #3
      Good pointers Mike!

      Ignition switch is new, but I have indeed already tried wiggling the key to see if it provokes the fault.

      Not sure on the earth wire; I think that isn't used with Powerspark, but I guess it couldn't hurt anyway.
      The answer isn't 42, it's 1/137

      Comment


        #4
        I've had a 'Powerspark' module fail with exactly those symptoms. Only did it when engine / dizzy hotter than normal (sitting in traffic after a good thrash).
        It got progressively worse over a few weeks. Changed it for the spare I carry & problem went away.
        Also elongated the holes to give a small gap with magnet ring. Kept the same mounting plate, so just need to carry a small Allen key for changing it if the same happens again - I always have a spare onboard.

        Comment


          #5
          That sounds both disappointing (that the things can give up the ghost) and encouraging (that my symptoms seem to match yours)! Come to think of it, the cut outs on mine, as far as I can remember, were on the Autobahn and in town, but not on a nice relaxing drive along B roads. I'm guessing that the rotor rubbing on the module didn't help the temperature aspect of things.

          Having to elongate those holes is nuts. I bought mine as recommended from a reputable Stag supplier as being a top product.

          I'm now trying to work out the wiring which I did! In the instructions it says "connect BLACK to the negative terminal of the coil ensuring no other wire is on that same side". At the time, I interpreted that as meaning the black wire in the distributor, so I chopped that. On the coil -ve there is the wire to the rev counter. Any idea what the sentence in the instructions means?

          Drew
          The answer isn't 42, it's 1/137

          Comment


            #6
            Instructions. I believe that although the ignition coil runs at 6v the modules are designed to run at 12v so they should not be powered directly to the ignition coil supply side which has both 6v & 12v when starting, and even when running the 6v volts is very spikey and not a nice constant voltage. The output from the electronic ignition, an earth, should be fastened to the ignition coil as normal, and yes the rev counter can be on the same coil connector as it is a passive connection and not supplying any voltage.

            If you have a supply side problem on the ignition where did you pick up a constant 12v feed from?

            Alan

            Comment


              #7
              No, but you have it wired the same as mine.

              I don't have a ballast resistor (MK2 wiring), and have bypassed the ballast wire, so am using a 3ohm non ballast coil.
              I reckon it's the heat that kills them, the dizzy gets really hot at that end of the engine - almost too hot to hold, my coil is mounted on the bulkhead.

              Comment


                #8
                Originally posted by barkerwilliams View Post
                Instructions. I believe that although the ignition coil runs at 6v the modules are designed to run at 12v so they should not be powered directly to the ignition coil supply side which has both 6v & 12v when starting, and even when running the 6v volts is very spikey and not a nice constant voltage. The output from the electronic ignition, an earth, should be fastened to the ignition coil as normal, and yes the rev counter can be on the same coil connector as it is a passive connection and not supplying any voltage.

                If you have a supply side problem on the ignition where did you pick up a constant 12v feed from?

                Alan
                A good point, got me worried, so just nipped out to check! When I made up my loom I ran an unballasted wire in parallel to the ballast one in case I wanted at some time to fit a different coil. It's this 12V supply I'm using

                Drew
                The answer isn't 42, it's 1/137

                Comment


                  #9
                  Ditch it Drew and fit a Pertronix, designed for the hot environment of a V8.

                  Comment


                    #10
                    The stag is fairly unique in it placement on the dizzy. American V8's have the dizzy at the front or way up in the air so don't get so hot.

                    I have a pertronIx module amongst my spares, don't use it because puts current through the coil without engine running, powerspark and accuspark don't do that. Found that out when I cooked a coil when working on my electric power steering pump and had the ignition on without engine running for half an hour. Coil was too hot to touch. Same would apply to old style points of course.
                    Last edited by NeilR; 7 June 2021, 08:38.

                    Comment


                      #11
                      Originally posted by KOY 23 View Post
                      Ditch it Drew and fit a Pertronix, designed for the hot environment of a V8.
                      Yes, I keep mulling over the idea - maybe one of the Winter jobs. As a purist, I originally wanted to stay with the double points, but setting up gaps and dwell were a real PITA, so Powerspark was my first venture into the world of electronic sparks, and I must say I never want to go back to points. Got am electronic box waiting to go into the Escort too at next opportunity. I think I bought Lemenition for it many years ago.

                      The answer isn't 42, it's 1/137

                      Comment


                        #12
                        Hi Drew...Ive had a similar thing happen be ok for weeks then ignition dead then back on again, sometimes it happened when I put foot on brake, turned out to be a bad connection on fuse box.

                        Comment


                          #13
                          Yeah, those faults which only occur every few weeks whilst driving are really a pain to find!
                          The answer isn't 42, it's 1/137

                          Comment


                            #14
                            [QUOTE=NeilR;n819872]The stag is fairly unique in it placement on the dizzy. American V8's have the dizzy at the front or way up in the air so don't get so hot.

                            I have a pertronIx module amongst my spares, don't use it because puts current through the coil without engine running, powerspark and accuspark don't do that. Found that out when I cooked a coil when working on my electric power steering pump and had the ignition on without engine running for half an hour. Coil was too hot to touch. Same would apply to old style points of course.[/QUOTE

                            Dont forget that a V8 sparks twice as often as a 4 cylinder so has more heat to dissipate.

                            Later Pertronix modules switch off after a period of no start so do not overheat the coil, surely forgetting to turn off the ignition is a rare occurrence​​​​​​?

                            Personally I would prefer a reliable unit in my engine rather in the spares box.

                            Comment


                              #15
                              Drew.
                              I have just confirmed with Powerspark that the metal base on the unit IS part of the circuitry, and must be "Earthed". This means that the original small wire between the base plate and the distributor body must still be in place, as without it, movement of the base plate created by the vacuum advance, could cause intermittant circuit breaking.
                              I have had my unit for many years, working in conjunction with the ballast resistor, and it has been entirely satisfactory, even in the hottest weather.
                              Mike.

                              Comment

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