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Thread: Help! No start, possible ground pulse problem?

  1. #1

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    1990 Mitsubishi Mighty Max
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    4G64

    Help! No start, possible ground pulse problem?

    1990 Mighty Max 2.4l
    Developed rough idle and then hard to start. Problem then led to no start. After tons if reading and asking I was told to check ecu for bad caps. Found two that looked burned nd leaking so I (not a pro solderer) thought I fixed but was to no avail. Sent ecu to rebuild company and was said it was repaired and it had a secondary hardware failure. Still no start.
    A lot of reading and testing and this is what I have - No spark from coil to plugs. 12v at both coil wires with spec ohms to primary and secondary but no ground pulse (gp).
    12v on 1 0v on ign. control module but no gp. Distributor is putting out 12v. 2@4.96v and a ground with both 4.96v showing gp. Also, white line, pin #4 from ecu has no signal that I can detect.
    My understanding is signal from dist. goes to ecu that sends gp to ign. control and travels to coil to create spark.
    Would this mean the ecu is bad (?)and I need to return for repair since it comes with life time.
    Sorry for the long wind and I am sure confusing way to ask question.
    Thanks

  2. #2

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    Adelaide, South Australia
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    1985 Mitsubishi L200
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    First question - have you done an error code check and what did it reveal? Here's the tricky situation. 1990 build trucks had a one year only production run using this particular ECU and peripherals (air sensors, tps etc) so if it goes bad you only have the option of finding one from the same year model. Next question - are you getting any signal from the distributor? The ICM in the distributor triggers both ignition and injector pulse so if it goes bad you won't get either events taking place (no fuel, no spark...)
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  3. #3

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    1990 Mitsubishi Mighty Max
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    Had two codes 1) airflow sensor and 2) baro pressure sensor. However those codes were on when running fine.
    As far as the dist. it has a 12v line, a ground and two 5v lines on the output and the 5v lines ground pulse showing with one at ckp speed and the other at cmp speed.

  4. #4

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    Long Beach,CA
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    1985 Dodge Ram 50
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    G54B
    I had a no start issue as well, it turned out that I was getting too much voltage for my newer parts, the new alternator, starter and battery that were installed made it profound. I have a 85 ram 50 royal and it was something in line of relays and further regulators, the newer 90s ones possibly have more gimmicks when it can come to these no starts though as well. Well just to state my own symptoms that I did end up. Best of luck.

  5. #5

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    1990 Mitsubishi Mighty Max
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    Nothing new has been added since it was running but thanks for the thoughts.

  6. #6

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    1990 Mitsubishi Mighty Max
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    Question, had ecu repaired and after install at the power transistor I get 12v line to coil, black is grounded and a white from ecu shows ground but does not pulse. Should the white line feeds the transistor have a pulse so it can feed the ground to the coil?

  7. #7

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    1990 Mitsubishi Mighty Max
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    Okay, trying again. Found out how the transistor properly functions. I have ground, 12v and a white ground that generates 54mv pulsing trigger signal from the ecu. Numbers on both sides of the transistor are good . Still no spark. Distributor and related ignition parts have all been checked.
    What am I missing and any others ways to check, jumpers for exam
    Thanks
    Any help would be greatly appreciated.. Usually don't get many replies in electric.

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