Ideas for diagnosing ignition problems

Discussion in '40- & 55-Series Tech' started by antidamage, Dec 13, 2013.

  1. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    So I've been having some ignition problems. My 40 was running a bit rough and rather than just replacing the stock parts with more stock parts, I sprung for an Accuspark electronic ignition upgrade.

    The first thing I discovered is that the ballast had been removed at some point in the past, which was probably why everything was wearing out much faster than expected.

    So I replaced the distributor internals with the Accuspark ignitor, got a new rotor and cap and replaced the ignition coil and spark plugs with some with a bigger gap. I ran a new switched ignition wire to the ignition coil because the old one had a fair amount of resistance in it.

    After doing all this, no spark. The guy who sold it to me took a look and said everything looks fine.

    So I took it back to stock, no spark.

    I've tested the following:

    • Putting a multimeter from the positive terminal on the ignition coil to the battery earth with the ignition switched on I'm getting around 12v.
    • Putting it across the negative terminal and the battery earth I'm getting about 1v.
    • Pulling a sparkplug out and resting it on the negative battery terminal while it's still plugged in gives no spark.

    Fairly sure the ignition leads are OK. Should I also be disconnecting the condenser? I've tried it both with and without it.

    What else can I test? The thing hasn't run in about two months and I'm starting to get antsy to drive something. The last time I took it to a sparkie I got charged $900 to replace the battery so I'm really keen to avoid going back.
    Last edited: Dec 13, 2013
  2. DougAustinTx

    DougAustinTx

    Messages:
    553
    Location:
    Austin TX
    I have no knowledge about Accusparks, but ignitions are really simple. Your ignition switch provides 12v to the positive on the coil (or 9 volts if you go through a ballast resistor) when the key is on. All the rest is simply connecting and disconnecting the negative terminal of the ignition coil to ground at the right times. You probably have a reluctor wheel in the dizzy that spins on the shaft, right? The reluctor has 6 small magnetic fins that need to be within about .010 from the pickup coil in the dizzy. The pickup coil opens and closes the circuit to ground at just the right time to fire the plugs. The ignition coil actually fires when the connection to ground is BROKEN. There are many threads on here that get into diagnosing the lack of spark.
  3. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    Thanks for the reply, I didn't know it fired when ground breaks. I can try and make a spark manually without any distributor components.

    Well, I'm out of ideas as to what might be wrong. I might go pick up a new set of HT leads today and see if that helps. They tested fine but I've got nothing else that hasn't been replaced.
  4. DougAustinTx

    DougAustinTx

    Messages:
    553
    Location:
    Austin TX
    You only need the high tension wire that goes from the coil to the dizzy to do the testing. Ohm it with a meter and see if it has 3000 ohms or less (the less the better). Plug one end into the coil HT terminal and get the other end's metal clip within a quarter inch or so of the neg. battery terminal. The ignition on my '76 and my '79 is stock and will jump about an inch to ground. No sense buying cables if that's not the problem. If your pickup coil in the dizzy isn't adjusted properly, or it's bad, you will never get a spark. You can eliminate the whole dizzy issue by just running a wire from the coil neg. terminal and brushing it against the neg battery terminal, also you need 12v to the coil when testing.
  5. Gumby

    Gumby Supamod Staff Member s-Moderator

    Messages:
    11,105
    Location:
    Knee deep in hookers and gin
    1v from the battery terminal to the engine is a little high. It should be less than .5 under load. Check your chassis ground too. I doubt that's your problem, but since you noticed it I thought I'd mention it.

    Accuspark is a good system, but they do go bad, especially when hooked up wrong. Is yours new or used? Do you have the part that goes around the cam in the dizzy?

    12v to both the red wire on the accuspark and + side of the coil and straight to the - side of the coil with the black wire from the accuspark.

    It's possible the coil is cooked too.
  6. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    The accuspark kit is new. I'm 99% positive that it's fine, hasn't been hooked up the wrong way, etc. The guy who sold it to me came out and checked it as I needed him to bring out a slightly bigger magnet ring for the cam.

    I've got two brand new coils here, both test fine for resistance between the HT plug and the side pos and neg.

    Where's the chassis ground normally? That could well be it.

    If I've got this right, I need to put the HT lead from the coil near to the battery, get some juice going through it then disconnect the negative terminal from the coil to get it to fire. Is that right? Or was that the negative disconnecting from the dizzy that causes IT to fire? I've tried the first step already and get nothing.
  7. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    The HT cable has just over 300ohms resistance. I checked negative to the battery negative and it's more like .08 volts, not 1. I overgeneralised. ;)

    Then I did something I normally wouldn't. I couldn't get a spark to the neg terminal so I put the multimeter right in there set to 600v and the ht lead is only putting out 12v when it's just sitting there with they key on. Same for the other coil. Does that mean they're both blown

    When I check the coils, the accuspark (internal ballast) is 8k ohms and the c80r (no ballast) is 15.8k.
  8. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    So I have a brand new ignition coil here. I hooked it up to the ignition, earthed the negative terminal to the battery and ran a new wire from the HT plug and left a gap of 1/4 of an inch between the other end and the battery. No spark, even when I brush the terminal with it. There's actually more spark between the earth wire of the ignition coil and the battery than the HT line.

    The battery is fully charged, the wires were all fine with the ignition being 12v hot, the resistance on the new coil is 18k ohms.

    What now guys? Have I tested it correctly? This is driving me mental.
  9. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    Just checking the absolute basics here.. the + terminal on the ignition coil goes to the wire that connects to the ignition, correct? The - terminal goes to earth (or the distributor when I'm done testing this part of it).
  10. DougAustinTx

    DougAustinTx

    Messages:
    553
    Location:
    Austin TX
    Yep, plus on the coil goes to the ignition wire (or to the + on the battery during testing). Neg. on the coil goes either to the dizzy points or electronic grounding module, or temporarily to the battery ( - ) during testing. The ground wire during testing would be sort of touched against the neg. battery terminal, then removed. The collapsing magnetic field energizes the secondary windings in the coil to produce a high voltage spark. You are converting low voltage/high amp battery voltage to high voltage/low amperage energy.
  11. bikersmurf

    bikersmurf

    Messages:
    5,728
    Location:
    Victoria, BC
    I'd start by testing the coil. Connect a spark plug to it with a plug wire, and use a jumper cable to connect it to ground. Connect the + side of the coil to the battery and ensure it's getting 12v, tap a grounded wire to the negative side... You should have a big fat spark.

    If that works, try connecting the - side to the distributor, and trying again. Continue adding things till something doesn't work... And then ry to figure out why.

  12. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    Got it. I'll try now.
  13. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    Alright. So, I got spark but it was so weak that it's barely visible. I found an old, smaller sparkplug with a smaller gap and tried all three ignition coils and they all give a tiny, weak spark.

    I've thrown the battery on to charge some more in the hope that that will help.

    Why is the spark so weak? Could it be the gauge of the wire that I'm using to test it, or the fact that I'm just holding the wire to the terminal to get it to connect?
  14. Pin_Head

    Pin_Head

    Messages:
    11,818
    Location:
    OC, CA
    The spark voltage and intensity increases with the distance it has to jump. As long as it makes a spark it is OK. A "stronger" spark has no extra beneficial effect.
  15. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    Got it.

    I guess my next step is to try to figure out the correct stock configuration so I can get it back to that.
  16. bikersmurf

    bikersmurf

    Messages:
    5,728
    Location:
    Victoria, BC
  17. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    Took me several weeks to realise this is literally how it's set up. The setup when I got it was so odd with everything tucked away inside the distributor that I couldn't work out where the points actually go. So just confirming because my starter motor isn't going and I can't test it...


    Ignition -> coil positive
    Coil negative -> splits off to points and condenser

    Is that how the condenser is hooked up? What does it do, anyway? It was originally jammed INSIDE the distributor under the rotor, so now I've got it on the outside like in most of the photos I've seen.

    Edit: this one is set up identically to how mine used to be: [​IMG]
  18. antidamage

    antidamage

    Messages:
    93
    Location:
    Auckland, NZ
    Nearly got it going. The distributor is put back together as per the image above and fires in the correct order.

    When I actually go to start it though, when the engine tries to fire it makes a sound like a cat coughing and halts. I'm 100% positive the rotor is in the right position and the leads are in the right place at both ends. I'm also noticing that when the engine tries to fire the fan reverses direction briefly.

    What could be causing this? Could the starter motor somehow be going in the wrong direction? Could the timing be so far off that it's causing it to do this?
    Last edited: Jan 24, 2014
  19. DougAustinTx

    DougAustinTx

    Messages:
    553
    Location:
    Austin TX

    There are 6 high spots on the dizzy cam that slightly open the points. When the points are open, do you have .018 of an inch in the gap (measured with a feeler gauge)? If the gap is correct and it's causing the engine to kick back when trying to start, your distributor housing needs to be rotated (probably clockwise) a little at a time until it fires correctly. If you don't have enough rotational adjustment, then you need to do the whole routine of getting the #1 piston at TDC on the compression stroke, locating the bb on the flywheel, and possibly removing the dizzy, repositioning the oil pump shaft with a screwdriver down the dizzy hole, then reinsert the dizzy and make sure the housing fully bottoms on the engine block and the rotor is pointing at the #1 sparkplug wire in the dizzy cap. Good luck.
  20. ozcrusier

    ozcrusier

    Messages:
    726
    Location:
    Coffs Harbour Australia
    Sounds like the leads are in the wrong position have you gone through the firing order with number one at TDC linning the leads up in firing order.

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