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Thread: Digital 6AL stalls, but always restarts.

  1. #1

    Default Digital 6AL stalls, but always restarts.

    I wonder if someone can help me diagnose an issue I'm having with my car.

    '71 Pinto with 289, MSD 6AL (6425), Pro Billet distributor and MSD Blaster SS coil, runs great 99% of the time, pulls good to the 7K limiter.

    Last summer it stalled a few times, usually at low speed in traffic like coming up to a light or just idling along, ignition cuts out, tach needle drops when it starts to stumble.

    This spring thought I found the problem. I dropped the steering column down to access the ignition switch and could get it to stall when I jiggled the switch. Replaced switch with one from a parts car.

    Yesterday had it out for a quick drive and it briefly stumbled/missed then ran fine, after it stumbled the tach was not reading. It drove fine for a few more minutes then stalled. I pulled over and it re-started fine and the tach was again working.

    When I got home I felt the box and it was warm to the touch (mounted on rubber feet behind the glove box).

  2. #2

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    Just a little update (Thursday). I ran the car some again, as it was idling and coming up to temp it stumbled/ momentarily cut out and eventually stalled. The LED light on the box was varrying bright to dim as it was stumbling. I confirmed constant 14V to small red wire during this condition. After I shut it off, I checked the resistance of pickup in the distributor and it’s just out of spec. 708 Ohms on 2K setting of my multimeter. How sensitive is the system to the spec of 500-700 Ohms? Any thoughts?
    Last edited by fozzy; 06-19-2020 at 05:47 PM.

  3. #3

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    Friday update. Today I pulled the distributor, attached the multimeter to the pickup leads, pre heated the oven to 200°F and set the distributor on the rack and watched the resistance for 35 minutes. Resistance started at 581 Ohms and climbed to 781 after 35 minutes.

    When the car would stall, it would most of the time be after it had warmed and usually after about 1/2 hour of driving, but not always. Once I wasn't sure it'd make it around the block it was backfiring and sputtering so bad. I'm leaning towards thinking it's a problem inside the MSD 6AL like a bad solder joint that acts up with heat.

  4. #4
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    Default

    I'd think that pickup resistance is going high enough to cause the cutout. How old is this distributor, and the rest of the ignition system? Gary
    Regards, Gary

  5. #5
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    Quote Originally Posted by fozzy View Post
    I'm leaning towards thinking it's a problem inside the MSD 6AL like a bad solder joint that acts up with heat.
    A long time ago, I had a CDI box that failed when hot. Very annoying until I found the problem. However, I'd replace that magnetic pickup first (due to the varying Ohms measurements).
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  6. #6

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    Quote Originally Posted by Gaz64 View Post
    I'd think that pickup resistance is going high enough to cause the cutout. How old is this distributor, and the rest of the ignition system? Gary
    The parts are all basically new, I'd say less than a hundred miles on it all. I bought the box, coil and distributor all in about 2014, finally drove the car last summer a few times and after a few short trips it started this shutting off business.

  7. #7

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    Quote Originally Posted by Danny Cabral View Post
    A long time ago, I had a CDI box that failed when hot. Very annoying until I found the problem. However, I'd replace that magnetic pickup first (due to the varying Ohms measurements).
    Are the magnetic pickups available separate from a new distributor?

  8. #8
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    MSD does sell the magnetic pickup separately for most of their distributors.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  9. #9
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    Quote Originally Posted by fozzy View Post
    The parts are all basically new, I'd say less than a hundred miles on it all. I bought the box, coil and distributor all in about 2014, finally drove the car last summer a few times and after a few short trips it started this shutting off business.
    Don't preclude the sensor harness connections, since the module is looking for a resistance loop, and any increase can be the reason for a cutout. So whatever value you have at the distributor, (looking at the magnetic pickup), you should also have close to that looking back at the distributor across the pickup harness, from the module end. You should also look for partial or intermittent short circuit, short to ground or voltage on the harness. My money is on the pickup, unfortunately. Gary
    Regards, Gary

  10. #10

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    Thanks Gents. I'll swap out the pickup and retry.

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