At my wits end.. Looking for any idea.

Discussion in 'Engine Performance + Maintenance' started by Shane Dyer, Jun 6, 2019.

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  1. 89GMCJOHN

    89GMCJOHN I'm Awesome

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    Temporarily bypass the relay control of the fuel pump (basically wire it direct) and go for a close to the house but long drive to heat things up and see if it ever shuts off again ...... FWIW.
     
  2. Schurkey

    Schurkey I'm Awesome

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    How hard can it be to test plug wires?

    1. Ohmmeter across the two metal terminals. Typical carbon-rope plug wires are on the order of 4000 ohms per foot of length. You have a three-foot-long plug wire, you better have less than 12,000 ohms. "Helical"- or "Spiral"-wound plug wires are under a hundred per foot, and "solid-core" wires are about one ohm per foot.

    I've seen cylinders run at idle or light load with a plug wire having in excess of 50 thousand ohms--but they may not run under heavy load. Also, this is very hard on the ignition coil, cap, and rotor including the carbon button built-into the cap.

    2. Connect the ohmmeter to either of the two metal terminals. Run the other probe over the outside insulation. Anything less than "open circuit" means the insulation is cooked. Check the boots as well. Sometimes the insulation has little burn-marks where the spark has been escaping.

    3. Look at the plug wires on a running engine IN THE DARK. Do you see them glowing? That's called "Corona Effect" and if they glow...they go. The insulation is in the process of breaking-down.

    4. LISTEN for the SNAP!SNAP!SNAP! of an escaping spark. A cylinder-balance test can find which cylinder(s) are not getting spark across the plug gap(s).

    5. IF (big IF) you have an automotive oscilloscope, (almost nobody does) look at the ignition voltage pattern for the secondary side of the circuit. Cooked wires show up clearly. Spark duration is very low, and there's little "ringing" of the waveform. If there's a short-to-ground, spark voltage can be very low.
     
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  3. Supercharged111

    Supercharged111 I'm Awesome

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    Can also observe plug wires in the dark for spark leaks. I've found a couple this way.
     
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  4. bowtie-72

    bowtie-72 OBS Enthusiast

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    Hate to sound overly simple here, but...is your throttle body squeeky clean inside and out? I know you said it was "sticking". I would get a can of throttle body cleaner and go nuts. Clean it inside and out, throttle plates, air idler, etc...
     
  5. Hipster

    Hipster I'm Awesome

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    This sure sounds like a weak coil that can't rise fast enough. 2-3 seconds miss 2-3 seconds miss.

    Tbi hit the nail on the head. An ohm test proves little. The voltage a coil builds goes somewhere. If it shorts it can backfeed the module and do damage. Bad plugs or wires can also take out a module.


    I too stay away from the $6 caps and $3 rotors and the cheapest ignition components.
     
    Last edited: Jun 24, 2019
  6. Shane Dyer

    Shane Dyer Newbie

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    Well fellas. I checked the fuel pressure and it was at 11PSI. Checked and changed a few more things and nothing seemed to make a difference. Well while I was letting it run I was around back just listening to the exhaust and i noticed a weird puff kind of sound. Decided to do the 'dollar bill' test. And... unfortunately it sucked it in occasionally. Therefore... ya boy has a burnt exhaust valve somewhere. So I've got a lot of work to do... but I'm on vacation this week. Sorry for the delay in response but wanted to give you all an update. Will check back in when that's done to let yall know if that fixed the problem.
     
  7. evilunclegrimace

    evilunclegrimace Does not always play well with others

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    A burned exhaust valve will NOT cause the issue that you described in your opening post. It will cause a miss at idle but it will not cause the engine to die and not restart.

    You stated that it dies and the injectors are not spraying fuel. Correct? You need to put a noid light on the injector plug when it dies and see if the injectors are actually being trigged when the truck dies. If the noid light does not show electrical pulses then you need to work backwards from there.
     
  8. sixteenacrewood

    sixteenacrewood Newbie

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    I had what may be the same problems
    Rough idle tuned out to be a bad egr valve, I cleaned it up and it idled better for about a week, I replaced it and cleaned the port and it idles great now, did it about a year ago.


    next problem
    Runs for a bit then dies, let it sit, starts back up, runs a bit then dies.

    Mine turned out to be the spark control module on the back of the distributor under the cap. Mine was simi new as well

    There is a heat dispersion grease under this little module, even on my new distributor it had dried up.

    The module heats up reaches critical temp and shuts down, it cools off and starts to work again until it gets hot again.

    If you replace it, pay very close attention to properly applying the grease and installing it correctly.

    I had this problem intermittently for a year or so, then it finally would only run about 5 minutes.

    Once I replaced the spark control module it has run perfectly, it's under $50

    I hope this helps!
     
  9. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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