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Thread: No spark

  1. #71
    Senior Member Bullitt's Avatar
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    Quote Originally Posted by Ron View Post
    That is exactly what I meant. You do NOT want to involve the w/s wire, only the coil.
    Here is a basic point system:
    Attachment 55485

    When the points close, voltage across the coil +/- 'charges' the windings up. When they break connection, the coil fires.

    We can replace the points and condenser with a simple switch (since the points are just a fancy switch, and the condenser is only for the points contact durability):
    Attachment 55487
    It uses a plug and coil wire to observe spark, but we want to test the coil alone, like this:
    Attachment 55488
    Note it is triggered on the (+) side of the coil instead.
    To be clear, use this way, making sure the air gap is reasonable....

    I shouldn't have added, "You might find it easier to see the spark if you remove the coil wire and use a short piece of wire from there (main coil terminal) to ~1/4 inch away from the (-) coil terminal...."! -- The test works using a coil wire and grounded plug. With a short piece of wire, it would probably jump to the grounding wire but it's not 100% and/or you might not see it. Sorry if that is what you tried instead of using a plug and wire. I edited in a note for future readers...

    EDIT: I found these that might help:
    https://www.youtube.com/watch?v=rJYJ3KvPhhY
    https://www.youtube.com/watch?v=5kvj_d72WTo
    Thanks!
    Tested it now like the videos show, and also in the car with w/s wire disconnected and using the wire harness for the + side. It sparked doing it both ways.
    Last edited by Bullitt; 02-25-2018 at 07:10 AM.
    Svein Apeland

    1981 DMC DeLorean DMC-12, VIN: 01598. Gas flap hood, manual transmission, black interior, wide stripe, galvanized frame, Spax and UK club exhaust.
    1973 Plymouth Road Runner
    x1979 Pontiac Firebird Trans Am
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  2. #72
    Administrator Ron's Avatar
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    Quote Originally Posted by Bullitt View Post
    Thanks!
    Tested it now like the videos show, and also in the car with w/s wire disconnected and using the wire harness for the + side. It sparked doing it both ways.
    Great! If the spark was strong, the coil and feed are OK. Now try it with the W/S triggering it instead of manually grounding it, by preforming the test in post 63. Make sure you let it spark to ground (the block)...with a jumper wire (then the coil wire to prove it if you haven't already;-)

    Still sounds like the cap-rotor since it was pulsing (trying to trigger) ever since you saw 'some' spark, else an intermittent problem...

  3. #73
    Senior Member Bullitt's Avatar
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    Quote Originally Posted by Ron View Post
    Great! If the spark was strong, the coil and feed are OK. Now try it with the W/S triggering it instead of manually grounding it, by preforming the test in post 63. Make sure you let it spark to ground (the block)...with a jumper wire (then the coil wire to prove it if you haven't already;-)

    Still sounds like the cap-rotor since it was pulsing (trying to trigger) ever since you saw 'some' spark, else an intermittent problem...
    Weird....
    Got the new plugs, plugwires, cap and rotor yesterday and replaced them all.
    No luck starting it.
    I did not perform the last test with the ws wire connected until i changed the cap and rotor etc...
    There was no spark. But now there is no spark when I ground the - on the coil either...

    I have checked/measured the ws wire down to the ecu and idle speed ecu... And it is all good. I have replaced some spade connectors around the resistor and checked/measured them as well.
    Svein Apeland

    1981 DMC DeLorean DMC-12, VIN: 01598. Gas flap hood, manual transmission, black interior, wide stripe, galvanized frame, Spax and UK club exhaust.
    1973 Plymouth Road Runner
    x1979 Pontiac Firebird Trans Am
    x1975 Chevrolet El Camino
    x1974 Plymouth Satellite Sebring
    x1966 Lincoln Continental
    x1983 Porsche 944
    x1982 Porsche 944

  4. #74
    Senior Member Bitsyncmaster's Avatar
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    The stock ECU will keep the negative side of the coil grounded when the engine is not running. So you would need to pull that wire off the coil to do the grounding test.

    Actually if all was working, you could just touch and remove that wire with the key set to on to get a spark. But with the engine not running your coil voltage will be lower than normal so you may not see a hot spark.

    It's best to test the spark with a plug wire from the coil attached to a spark plug. If you test through the cap your rotor may not be pointed to the plug your testing.
    Last edited by Bitsyncmaster; 03-01-2018 at 05:22 PM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  5. #75
    Administrator Ron's Avatar
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    +1 ...But he did the wrong test...

    Quote Originally Posted by Bullitt View Post
    Weird....
    Got the new plugs, plugwires, cap and rotor yesterday and replaced them all.
    No luck starting it.
    I did not perform the last test with the ws wire connected until i changed the cap and rotor etc...
    There was no spark. But now there is no spark when I ground the - on the coil either...

    I have checked/measured the ws wire down to the ecu and idle speed ecu... And it is all good. I have replaced some spade connectors around the resistor and checked/measured them as well.
    Ok, then the problem is intermittent, or you unknowingly changed something...
    I see...After seeing that it didn't work with the cap etc. on, you should try proving the coil again. But not by grounding the (-) coil terminal (because of what Dave said and the other things I mentioned before with that test). Trigger it from the (+) side instead... Sounds like it is not triggering, but let's go back to square one just in case and to avoid confusion-

    Set the test up exactly as below - no shortcuts, to see if it is the coil:
    BenchTest2.jpg
    If you get a strong spark, the coil is working properly. Otherwise the coil is bad.

    =====

    Next, the feed. Instead of feeding the momentary switch with battery (+) voltage, feed it with the stock feed wire from the resistors. (It is usually W/Y or W.)
    If you get a strong spark, the feed is working properly too. Otherwise, the problem is along the W/S wire back >>> toward the resistors >>>.

    =====

    Try the above first (in order, with a hot battery) so we are on the same page...
    If OK, the only thing left is the trigger circuit or an intermittent problem(s).

    =====

    You said you have checked the W/S wire back to the ICU. Note it branches several times. To be sure the W/S wire itself is OK requires disconnecting it from everything (Coil, Tach, ICU, RPM Relay, and Idle Speed Relay) then confirming that, in any key position, it has continuity to each plug/end, is not grounded, and has no power on it. A lot to do, especially the tach... So you might first try- Starting with everything stock, unplug the RPM Relay, Idle Speed Relay, and Main Coil Wire. Then see if it sparks from the loose end of a jumper wire inserted into the main coil terminal across an air gap to the (-) terminal when you crank the engine over with the key.
    If it does, plug the Idle Speed Relay back in, then the RPM Realy, one at at time, to see which circuit might be causing it to quit sparking...
    At this point we can decide how to continue with what you find...

    Watch how the tach acts with all of the above.

  6. #76
    Delorean Guru
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    When you are checking for spark the best place to do it is the wire coming out of the coil. That way you are not also checking the distributor. Once you verify spark out of the coil the next place to verify it would be to remove a spark plug and see if you get a spark there. If you are not getting a spark out of the coil there is no need to check a plug. If you aren't getting spark at the coil check the primary wire coming off the ballast resistor at the coil for voltage as I described before. It will turn out to be a wiring problem, a bad coil, or a bad ECU. The first two are likely, the 3rd possibility is unlikely. You should get a nice, blue spark at least 1/4" long as you crank. Check it to the block of the motor. Have the end of the wire held steady about 1/4", do NOT hold with your hand!
    David Teitelbaum

  7. #77
    Senior Member Bullitt's Avatar
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    Quote Originally Posted by Ron View Post
    +1 ...But he did the wrong test...


    Ok, then the problem is intermittent, or you unknowingly changed something...
    I see...After seeing that it didn't work with the cap etc. on, you should try proving the coil again. But not by grounding the (-) coil terminal (because of what Dave said and the other things I mentioned before with that test). Trigger it from the (+) side instead... Sounds like it is not triggering, but let's go back to square one just in case and to avoid confusion-

    Set the test up exactly as below - no shortcuts, to see if it is the coil:
    BenchTest2.jpg
    If you get a strong spark, the coil is working properly. Otherwise the coil is bad.

    =====

    Next, the feed. Instead of feeding the momentary switch with battery (+) voltage, feed it with the stock feed wire from the resistors. (It is usually W/Y or W.)
    If you get a strong spark, the feed is working properly too. Otherwise, the problem is along the W/S wire back >>> toward the resistors >>>.

    =====

    Try the above first (in order, with a hot battery) so we are on the same page...
    If OK, the only thing left is the trigger circuit or an intermittent problem(s).

    =====

    You said you have checked the W/S wire back to the ICU. Note it branches several times. To be sure the W/S wire itself is OK requires disconnecting it from everything (Coil, Tach, ICU, RPM Relay, and Idle Speed Relay) then confirming that, in any key position, it has continuity to each plug/end, is not grounded, and has no power on it. A lot to do, especially the tach... So you might first try- Starting with everything stock, unplug the RPM Relay, Idle Speed Relay, and Main Coil Wire. Then see if it sparks from the loose end of a jumper wire inserted into the main coil terminal across an air gap to the (-) terminal when you crank the engine over with the key.
    If it does, plug the Idle Speed Relay back in, then the RPM Realy, one at at time, to see which circuit might be causing it to quit sparking...
    At this point we can decide how to continue with what you find...

    Watch how the tach acts with all of the above.
    Checked the coil again.. It was ok. Next i checked with the + connected (w/y and w wire) while grounding - side... No spark. But when i pulled the upper spade connector I got a big blue spark from the coil.... But only when it was being pulled and connected. It also sparked from the resistor. Should it do that?

    See video

    https://youtu.be/h6f3ubNq4Dw
    Svein Apeland

    1981 DMC DeLorean DMC-12, VIN: 01598. Gas flap hood, manual transmission, black interior, wide stripe, galvanized frame, Spax and UK club exhaust.
    1973 Plymouth Road Runner
    x1979 Pontiac Firebird Trans Am
    x1975 Chevrolet El Camino
    x1974 Plymouth Satellite Sebring
    x1966 Lincoln Continental
    x1983 Porsche 944
    x1982 Porsche 944

  8. #78
    Senior Member Bullitt's Avatar
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    Upper right connection on resistor says 11,7 volts, lower right says 3,99 Volts. Left says 7, 83. Resistor is extremely hot. Could it be a short somwhere?
    Svein Apeland

    1981 DMC DeLorean DMC-12, VIN: 01598. Gas flap hood, manual transmission, black interior, wide stripe, galvanized frame, Spax and UK club exhaust.
    1973 Plymouth Road Runner
    x1979 Pontiac Firebird Trans Am
    x1975 Chevrolet El Camino
    x1974 Plymouth Satellite Sebring
    x1966 Lincoln Continental
    x1983 Porsche 944
    x1982 Porsche 944

  9. #79
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by Bullitt View Post
    Upper right connection on resistor says 11,7 volts, lower right says 3,99 Volts. Left says 7, 83. Resistor is extremely hot. Could it be a short somwhere?
    With the engine not running the resistors will run hotter than with the engine running. The stock ECU keeps the coil at ground and therefor your pumping max current through the resistors.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #80
    Administrator Ron's Avatar
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    Quote Originally Posted by Bullitt View Post
    Checked the coil again.. It was ok. Next i checked with the + connected (w/y and w wire) while grounding - side... No spark. But when i pulled the upper spade connector I got a big blue spark from the coil.... But only when it was being pulled and connected. It also sparked from the resistor. Should it do that?

    See video

    https://youtu.be/h6f3ubNq4Dw
    To be sure- Most schematics show a W/Y wire (feed) and a Y wire (condenser). Others show a W (feed) and a Y (condenser) wire, which I have seen on a couple of cars.
    Assuming you meant the "W/Y and Y wire", it is acting exactly as it should so far...

    It sounds like you were triggering it from the wrong side again- Instead of "+ connected (w/y and w wire) while grounding - side...", it should be, the ground connected while connecting-disconnecting (w/y wire) + side.

    Remember, when you connect a coil's (+) and (-), it charges up. When you disconnect it, by removing the (+) OR (-), is when it fires, to the nearest ground it can reach. Normally this "triggering" is done on the (-) side. It will fire ONCE only, each time the circuit is broke (normally triggered via the ICU).

    If I follow you correctly- When you removed the ground from the (-) side, breaking the feed circuit, you removed the only ground that the spark could reach! (Now, if you had a wire in the main terminal close enough to another ground source (block, cap, etc) instead, it should have sparked to it. But that is not the test...)

    Follow the test in the last post closely. Ground the (-) side (not with the W/S wire) THEN connect the W/Y wire to (+) side THEN disconnect (or switch off) the W/Y wire looking for spark from the main terminal to (-) or ground .
    [IF everything is correct, this is the similar to removing the spade connector feeding the resistors and why it gave the big blue spark from the main terminal, as it should...but also not the test.]

    I agree with Dave about the hot resistors and sparks in the vid. But you would have the cart before the horse using using the W/S wire at this point...

    PM sent

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