Testing a Stinger Power Module

Discussion in 'Sparky's corner' started by schwemf, Jul 13, 2023.

  1. schwemf

    schwemf Mike Schweitzer

    Are there tests that can be performed to verify the operation of a Stinger S-4 power module?

    I have a no-start problem with a Delco distributor converted to Stinger S-4. My air gaps (reluctor-to-pole-piece) all exceed .002", varying from .005"-.012".

    I'm seeing 500 mV-1600mV when bench testing the pickup.

    Disconnecting the coil wire from the distributor cap and cranking the engine shows plenty of arching to ground. But nothing to the #1 plug, as my timing light isn't flashing while cranking the engine.

    I'm seeing 12 volts at the positive terminal of coil with ignition on.

    The car has started twice, and started quickly (minimal cranking). But that's it.

    I swapped in a new distributor cap and new rotor, new coil. The plug wires have about 1,000 miles on them.
    Last edited: Jul 13, 2023
  2. schwemf

    schwemf Mike Schweitzer

    I found this advice from prior posts.

    Larry70GS: "If you go from the - side of the coil to a good ground with a test light, the light should flash as you crank the engine. If it does not, I would suspect the box. "

    Hooking up a test light as Larry describes and cranking the engine, I see the test light quickly alternate between a bright light and a dim light. I'm guessing this is what is meant by "flashing."

    Bob: "If the test light flashes while cranking, check for spark at the coil wire. If you have spark, keep checking down the secondary ignition line. If you don't have spark, suspect bad coil or coil wire."

    I see sparks from the coil wire to ground while cranking the engine. No voltage to the #1 plug if my timing light can be trusted.

    "If the test light stays on steady during cranking, suspect a trigger problem (pick-up in distributor or Stinger module)."

    The test light definitely does not stay on steady during cranking.

    "If there is no light on the test light on the coil neg during cranking, check the B+ side of the coil during cranking. If there is a light on the B+ side, then suspect a bad coil. If there is no light on the B+ side during cranking, then you have a wiring problem."

    Not my case, so it sounds like the wiring and the coil are OK. I did successfully bench test the wiring harness after installing a new, Packard 56, non-Stinger connector between the Stinger box and the distributor-mounted pickup.

    The car did start initially while performing these tests, but not on subsequent attempts.
  3. schwemf

    schwemf Mike Schweitzer

    With the ignition on, test light connected between coil negative side to ground, test light glows brightly. Rotating the distributor at this point has no effect, as the test light continues to glow brightly.

    I'm not convinced that the test light is flashing while I'm cranking the engine, or if the test light is simply dimming due to the voltage drain?
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Not sure if you can test the Stinger box the same way you do an MSD box, but I guess it's worth a try. Pull the coil wire out of the distributor cap and position it near a ground (or use a spark tester). Turn the ignition to Run. Pull the magnetic trigger connector apart, and using a paper clip or other wire to short the two wires together at the box end of the connector. When you break the connection, you should see a spark.
  5. schwemf

    schwemf Mike Schweitzer

    Yes, I do see a spark each time I break the connection.

    I have also tightened up the air gap within the distributor. It's now as tight as it can go (0.002") on the closest reluctor tooth to the pickup with vacuum advance applied.
  6. schwemf

    schwemf Mike Schweitzer

    There is some intermittent problem with the Stinger module, I believe, as I performed the above test again and this time I don't see a spark when breaking the connection.

    The car starts on initial cranking, idles very roughly at perhaps 100 rpm, then stalls and won't restart.

    Further cranking shows the timing light not blinking.

    I have re-seated the spark plug wires into the distributor cap (pulled out the terminals away from the insulation nipples, pushed the terminals firmly into the cap, then slid the insulating nipples back into position on the cap).

    Some of the rubber insulation on the new coil wire was damaged at the coil terminal, so I swapped in another coil wire. Testing with a multimeter shows continuity on both, but perhaps there might be a short with high voltage. I'm not sure. Again, this car ran fine when parked last Fall.

    Spinning the distributor on the bench at cranking speed shows at least 600 millivolts, so I believe the new distributor coil is not the problem.

    I've put together a points distributor and will be swapping that in shortly and will post my findings.
  7. schwemf

    schwemf Mike Schweitzer

  8. schwemf

    schwemf Mike Schweitzer

    The no-start problem was at least in part due to the thermostatic coil coming apart. I had cleaned it last fall and failed to reinstall the spring clip retainer. The net effect was the choke not coming off, flooding the engine.


    Replacing the distributor with a stock, points unit, and the car still had difficulty starting. That pointed me to the above mentioned thermostatic coil.

    Once the coil was fixed, and the points ignition installed, the car ran great, 35 miles to and from a cruise at highway speeds most of the way.

    Putting the Stinger back in, and with some difficulty starting it initially, it now starts quickly and idles smoothly. But it stumbles upon acceleration. Dwell is 15 degrees, according to my 2020 dial back timing light.

    Hooking it up to an oscilloscope shows a short during the dwell cycle at idle.

    IMG_20230812_175801124 (2).jpg

    Seems like this would indicate the control module and an errant signal to fire, which in turn hurts the available voltage?

    UPDATE: This observed pattern was due to improper probe attachments to the engine under test. The ground probe for the oscilloscope's ignition probes should have been attached to the ignition ground and not to just any ground. As soon as I attached this probe to the Stinger/Hayes wiring harness ground, the pattern improved immensely and this "other" voltage, which I though was a short, went away.
    Last edited: Oct 25, 2023
  9. schwemf

    schwemf Mike Schweitzer

    Seeing a dwell value of 15 degrees must indicate a fault in the Stinger power module.

    Isn't adjusting the dwell the power module's sole job?
  10. Stage 2 iron

    Stage 2 iron 480 IRON HEAD STAGE 2

    Points dwell was 28-30
  11. schwemf

    schwemf Mike Schweitzer

    Conclusion: In hind sight, I should have located a known good Stinger ignition and swapped in the components to identify any failure that I might have had. A buddy just sold his GS and kept his working Stinger. I wish I had known this before modifying the Stinger parts that I had.

    One of those modification was to use a different power module-to-distributor connector, due to the new pickup. I need to make an adapter to try my buddy's stinger components.

    Here's how to take the terminals out of the Stinger Power Module-to-Distributor connector:

    The male terminals are easy, with the tabs in full view. Depress them and pull out from the opposite side.

    For the female terminals I used a bench grinder on a paper clip to make a couple tools that are thin enough to slide into the housing for depressing the terminal tabs. Like the males, there are two tabs on each terminal. Slide in the narrowed paper clip ends and pull from the opposite side.
    GSX10/10 and john.schaefer77 like this.
  12. Guy Parquette

    Guy Parquette Platinum Level Contributor

    Wow, learned a bunch here. Good thread!
  13. schwemf

    schwemf Mike Schweitzer

    According to "Chrysler Master Tech - 1972, Volume 72-3 Ignition Systems for '72"

    "A dwell meter will give a reading, however the design of the control unit circuitry cannot be measured with a dwell meter."

    I'm assuming this applies to the Stinger too, since it seems to have been derived from a Chrysler electronic ignition of this vintage.
  14. 1973gs

    1973gs Well-Known Member

    I see a problem with the installation. They hook up the MSD box directly to the battery with no fuse. When I installed my FAST fuel injection system, it states that the positive and negative wires must go directly to the battery. I installed a fuse at the battery. Several years later when I was diagnosing an issue, I find that FAST has a fuse in the power wire, but it's in the harness 5" from the ECM. This does nothing to protect the 10' of wire running from the battery to the ECM in my dash. I guess that they aren't concerned about your car catching on fire.:eek:
  15. schwemf

    schwemf Mike Schweitzer

    Testing my power module with a know good, thank you Pete Tomka:
    "Hays" branded module
    yellow to black 1.614 M ohms
    green to black 10.96 M ohms
    red to black 11.05 M ohms
    white to black .333 K ohms,
    ( K ohms is 1,000 ohms so .387 K ohms = 387 ohms; M ohms is 1,000,000 ohms)

    My module, branded "Stinger S4", showed infinite resistance on all wires to black ground.

    Another, unknown unit, probably fine, tested:
    "Hays" branded module
    yellow to black 1.123 M ohms
    green to black 14.45 M ohms
    red to black 14.48 M ohms
    white to black .387 K ohms

    Swapping in the know good, my car still loads up on idle, but the stumble, though still present, is less. Time for new plugs.

    Last edited: Sep 30, 2023
  16. schwemf

    schwemf Mike Schweitzer

    I've found the problem!! The distributor pickup was malfunctioning! The replacement that I tried, SMP LX-109, didn't fit (i.e. insufficient adjustment to get the necessary 0.002" reluctor gap), so I pried off the pickup coil and installed it on the old Stinger/Hayes pickup reluctor. Perhaps I damaged the coil during this swap.

    By the way, although Chrysler warns that the dwell readings are inaccurate with this style pickup, the malfunctioning pickup showed a dwell of 15 degrees at idle whereas a good original Stinger/Hayes pickup showed 34 degrees.

    Off to Napa to see if I can find a direct, bolt-in replacement.
    Last edited: Oct 1, 2023
  17. schwemf

    schwemf Mike Schweitzer

    Despite the different resistance readings, all of the three modules above fundamentally work. Installing each and racing up and down the street showed no issues. I hope to put some miles on each just to be sure they're Okay.

    At this point it appears that all the problems that I was experiencing were due to the pickup malfunctioning and subsequently fouling the plugs. With the known good pickup, and new plugs, all issues are now gone.

    The different resistance readings between the "Hays" and "Stinger S4" branded modules must be due to different electronics. Schematics would answer this question, if any are available. It would be helpful if those of you having a module or two sitting on their shelf could please quickly test theirs as it would be interesting to know if my measurements are typical for the different branded modules.
    Last edited: Oct 1, 2023
  18. schwemf

    schwemf Mike Schweitzer

    I reinstalled my original Hayes/Stinger reluctor pickup coil on the original Hayes/Stinger pickup and, using the know-good power module, and the car is running beautifully. So the SMP pickup coil that I used was defective, or I broke it removing it from its pickup, or ??? In any event, the distributor is now once again all Hayes/Stinger components.

    I'll drive the car for awhile now to verify all is OK, then swap out the known-good power module for mine.

    Progress is being made!!
    john.schaefer77 likes this.
  19. schwemf

    schwemf Mike Schweitzer

    All of my original Stinger/Hayes components (i.e. pickup, control module, coil) have been reinstalled and the car is running like its old self.

    My problems were caused by malfunctioning choke components, and an original carburetor trying to provide proper idle fuel to an engine with a KB118 cam.

    Here are the root causes of all the issues that I was seeing:
    1. Choke thermostatic coil missing retaining clip, which allowed it to come apart, preventing choke from opening fully after cold start
    2. Choke secondary vacuum break misadjusted, not allowing choke valve to open more fully seconds after cold start. Note both primary and secondary pull-offs were working, car cold started nicely, but failed to open the choke valve sufficiently to warm up quickly. The added fuel from the too closed choke valve fouled the plugs and loaded up the engine when attempting not-fully-warmed-up acceleration.
    3. Oscilloscope probes not grounded properly, which I believe resulted in the scope picking up other voltages present (e.g from the alternator perhaps). A Motor magazine article from 2006 advised when probing a circuit, the ignition circuit in this case, attach the ground probe to the ignition circuit ground. Doing this resulted in a much "cleaner" voltage measurements of only the ignition circuit. The phantom voltages that I had though were shorts went away. In summary, when using an oscilloscope, ground probes needs to be attached to the ground wire of the circuit under test and not simply to any ground!

    This car has a KB118 cam and had blocked heat risers when I purchased it. The idle was set at 1100 rpm. Wanting to drive this once show-only car, I removed the plugs to open the heat risers, got the choke to work, and dropped the idle to 850 rpm. But I failed to rework the stock Rochester Quadrajet's idle circuit to provide adequate air/fuel mixture at idle. Instead, I set the car up with 19 degrees advance at idle (12 initial + 7 vacuum). This crutch works, though not ideal. The idle mixture screws have limited effect on idle rpm and the exhaust stinks.

    My next step is to follow Chris Ruggle's (https://cliffshighperformance.com/) recommendations for modifying the idle circuit which, in addition to helping the idle, should also help the choke circuit as well. I'll start a new thread for this work.
    Brett Slater likes this.

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