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Thread: X7 Weird Issue: No spark.

  1. #1
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    X7 Weird Issue: No spark.

    Little bit of history first:

    X7 I bought off a friend. He blew a headgasket then decided to take a year to put it all back together himself. Once it was back together it wouldn't start. He took the car to a shop who diagnosed it as a bad ECU. Then he ran out of money so I bought it... - great move.

    So far I have:

    Checked Dizzy - resistance and air gap are correct - tried second dizzy to no avail.
    Checked Igniter and coil - Both good via FSM diagnostics - also tried a different igniter and coil with no success.
    Checked continuity to ECU from ignition parts - all good.
    Tried second ECU - still no spark.
    Tested all relevant fuses and relays - they come up good.

    I am getting OBDI code 12 - No signal from pickup - Which is consistent with the tests I have done... however nothing seems to be at fault.

    I can trigger the coil manually and get spark.

    This car is driving me a bit crazy. Even had my friend who is a very competent mechanic - especially with electronics - look at it and he's stuck. What am I missing? I have to be missing something about the way these ignition systems work... or something simple.... Help plz?
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    End.

  2. #2
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    Might sound a little silly, but is the dizzy getting drive?

    Is the engine itself well grounded?
    1JZ 1984 Celica GTS
    1UZ 1981 Corolla sedan
    ? 1972 Celica race car

  3. #3
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    No pickup signal means the PCM isnt seeing the pulses from the variable reluctance (VR) sensor in the dizzy.

    It's been a while since I've worked with these, I think the VR signal goes into the igniter module for conditioning and then to the ECU so it can figure it's **** out - correct me if im wrong. anyways the VR signal will be a low voltage AC signal while cranking, 0.2V maybe? check that while cranking.

    also related to engine grounding: the igniter modules (aluminum can with fins attached to the coil) MUST be grounded at its case. I go so far as to add an extra ground wire to one of the mounting screws, and always check continuity from the igniter case to battery -

  4. #4
    visean's Avatar
    visean is offline Yo, troubled night in the John
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    Quote Originally Posted by Sparkie View Post
    It's been a while since I've worked with these, I think the VR signal goes into the igniter module for conditioning and then to the ECU so it can figure it's **** out - correct me if im wrong. anyways the VR signal will be a low voltage AC signal while cranking, 0.2V maybe? check that while cranking.
    That's right if it's a VAST system in x7: Basically the hard to process sine wave from the VR sensor gets conditioned into a Square wave there for easy processing.

    Good engine ground is a good place to start. Use a multimeter to check resistance between several places on your block to the negative side of you battery... you should see very low resistance. Having all of the factory grounds in place doesn't mean you have good engine ground.

  5. #5
    visean's Avatar
    visean is offline Yo, troubled night in the John
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    Quote Originally Posted by clay72 View Post
    Might sound a little silly, but is the dizzy getting drive?

    Is the engine itself well grounded?
    That's an interesting thought.... of course there'd be no signal if the cam pickup wasn't rotating...... ONly way I could see that happening is if the dizzy is broken internally (you tried a second)... or the timing belt is broken (HG just done means that there's a new timing belt on right?) Or did your friend forget to put the timing belt on, but put all the covers back on? haha

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