HEI question

Discussion in 'Troubleshooting & Diagnosis' started by rumrunner, Feb 2, 2008.

  1. rumrunner

    rumrunner New Member

    Jan 8, 2008
    Atlanta Georgia
    I have a 350 with the HEI distributor, the car was running fine, the other day it wouldn't start, i left and when i returned several hours later i managed to get it started, seem to run fine.
    Today I went to start it and it won't start, have gas and the compression seems fine, i put new plugs in it because the others looked black and i wanted to start the troubleshooting at least with a new set of plugs. I poured some gas down the carb and put several in the tank, still won't start, i pulled a plug and wire and grounded it, the spark is yellowish, i suspect a week coil pack or the module inside the distributor.
    I'm not up on the Chevy HEI stuff, can the coil weaken before it goes out? or is the weak spark (yellowish) because of the module?
    Any help appreciated.

  2. TheFly

    TheFly Guest

    Well maybe, starting fluid is the best check on that. If it won't even pop off on that, bad spark for sure.

    Id say change wires next, or pull coil n modual n have checked at auto store.
  3. TheFly

    TheFly Guest

    If ya got a timing light hook it up also to make sure its firing all the time.
    Light flashes with ever spark fire, so it will tell ya if its firing proper.

    If the magnetic pick up goes it can have random weak spark. Mine actualy ran with a bad pickup but not well as it only fired every other time.
  4. rumrunner

    rumrunner New Member

    Jan 8, 2008
    Atlanta Georgia
    Well I have spark, just seems weak, it's yellowish, not blue. Is the module inside just to fire the coil on top?
    I'm think the coil has a partial short and isn't amplifing the the voltage enough.
  5. TheFly

    TheFly Guest

    well in cap coil HEIs aare pron to fail, the coil is epoxy filled so it run hot as is, then its all closed up in the cap making it worse.

    I run HEI but external coil and only oil filled can coils.

    Take the stuff into autozone or other they can test your coil or modual.

    how old are the wires???
  6. rumrunner

    rumrunner New Member

    Jan 8, 2008
    Atlanta Georgia
    wires are like new, i just went to a couple of parts stores, O'reilley's and Autozone, and asked them about HEI dizzys, ya might as well be talking to a deaf dumb and blind monkey!
    Summit has a rebuild kit with cap, coil, module, rotor, and new vac advance for 60 bucks!
  7. hucks 70

    hucks 70 Veteran Member

    Jun 4, 2004
    millstadt ill USA
    :bowtie: change the module
  8. -=79z28=-

    -=79z28=- Veteran Member Lifetime Gold Member

    Jan 22, 2008
    Charlotte, NC
    i second that, hucks. i had a similar experience, i was in the drive thru at wendy's and my truck just shut off out of the blue. my dad came with some tools and the extra module he made me buy (thanks dad, you know everything). i put it in, and it fired right up. the first time a module goes out is a time you will never forget, especially if you driving down the road!
  9. 74 Z28 dude

    74 Z28 dude Veteran Member

    Mar 23, 2005
    North Bend, WA USA
    My personal experience is with mainly GM HEI modules as that is what is in 99% of the GM vehicles that come into our dealership. What I have found is that when a GM HEI module fails it provides NO spark. However aftermarket(non-GM) modules can provide many different failure scenarios. Yellowish spark is one. The reason being that aftermarket modules do not have nearly the internal circuitry. We have cut them open to see. I suspect the transistor driver that controls coil saturation(current flow) is of low quality. If you in fact have a GM module then investigate the ignition system supply voltage. Although I agree, it ran great prior, so I also suspect the module. Good luck!
  10. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

    Feb 26, 2004
    Bloomington, MN
    My nieghbors' truck had the same problem.... It had spark but is was yellow/orange. A new coil solved his problem.

    I've had a module die on me too... Thee was no spark for mine.

    Geat price on the rebuild kit! A module will cost $25 alone.

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