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MSD - battery drain
Is it likely that a faulty MSD ignition controller would drain a battery in a day? I jumped in the car after a day in the office (battery was charged when I got there this morning) and she was dead as a stump. I mean flatline. Single click on the starter relay. Key out, no electrical components left on. It was easy to jump start off another car's battery. I've already been experiencing monemtary power outages when motoring out of a traffic stop, so the ignition system is already under suspicion.
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Get your battery checked out. You might have a bad cell in your battery.
Alternator charging? If your alternator is not charging and you are running off your battery, when it goes dead so does your ignition. Check alternator. Check battery. Good places to start. DD |
My MSD was wired "conveniently" - that meant they wired the +12V and switch to the hot side of the ignition key. When mine blew up (oh yeah, did I forget to mention that?) I wired it properly - power directly to the battery and switched power to the switched side of the ignition. My battery now lasts more than 3 or 4 days with the ignition key off and the battery cutoff in the "on" position.
So that's something for you to try - try turning the battery cutoff off and see if it lasts longer. If not it's the battery(batteries). |
DD, the battery is fairly new. I also have a fairly new alternator. The electrical system was great when I left the house this morning. It did fine all the way home after a quick jump. A dead battery after a few hours of sitting - with all things considered - was highly unexpected.
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I've been driving this car for eight years with the current wiring scheme. Something has gone south fairly recently.
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After a 30 minute ride home, the battery is now charged. After she sat for an hour or two, I went out and turned the key - she spins and fires right away. It's got to be that MSD box!
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ignition Switch
Check the ignition switch. I think this could explain the problems.
Brent |
Tony, I wasted half a day trying to start my ERA for the first time with a brand new battery that had a bad cell. Once I jumped the battery my Cobra fired right up. I hadn't yet learned that it was a bad cell.
My battery was a brand-new, brand-name battery. After suffering "drainage" issues with it for a month or so (some situations more embaressing than others...), I took it out and dragged it down to the parts store where they tested it. Bad cell. Replaced it. Now I have no "drainage" issues. It's worth checking. Could save you poking around with a lot of wires and scratching your head... DD |
Tony:
MSD boxes get blamed for many things that ultimately turn out to be something else. The energizing of the box through the swiched 12 volt souce with the small Red wire is what turns the box "ON". 1. Disconnect this wire and see if the problem persists. 2. Next check for current drain at your fuse panel. 3. Lastly have the battery checked for a bad cell, even if it is a relatively fresh battery. 4. If all of the above check out look to the ignition switch. MSD units can and do stay attached to the battery and ground with the 10 Gauge wires for weeks at a time without any significant drainage on the battery. Good luck |
What Rick and most others said...
On a scale of 1 to 10, 10 being the most probable cause of your battery drain, I'd give the MSD box a 2. There's an easy way to check though... Disconnect your MSD box ground wire(s) and with the car off and momentarily touch the wire(s) back to ground. If you've got enough drain that it kills your "good" battery in 1 day then you'll definitely see a noticeable spark when brushing the wires against ground. The professional way to do it would be to again disconnect the box's ground wires with the car turned completely off, in the battery drain mode. Place a voltmeter between the ground wire(s) and actual ground. If you've a battery drain you'll read a voltage. The amount of volts read will be proportionate to the amount of drain. |
I was told by my engine builder that the ignition switch could be suspect. I agree that the MSD box is easy to target for blame since it's probably the most complicated component under my hood. The battery dying in conjunction with the fact that I experienced my "vapor lock" problem with a cold engine leaving the restaurant the other night should eliminate some of the suspects. Ignition switches are cheap, so I think I'll make replacing that the next action. If that fixes it, Brent and Lyle get the kudos!
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Placing a voltmeter in the circuit will not work, you need a ammeter to measure current. |
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You're telling me you have a voltmeter connected between your disconnected ground wires and ground. Of course you'll read something, that's not how you look for voltage drops. |
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...not looking for voltage drops (that's not what we're doing anyway), looking for MSD box power drains through the box's ground circuit(s). If everything's off ... no, you shouldn't read voltage. |
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I would think not (MSD drain). I would keep looking. Have you load tested the battery to see if it will hold a charge, in the first place? If I remember correctly, you can check for a drain by placing the probes of a VOM between the Neg battery post and a ground. There should not be any negligible reading. How about a "wayward" clock, bulb lit somewhere? I had a trunk light in my old corolla not go out. |
I don't think you are looking for voltage drops here, but rather a current draw. Amprege
A volt meter in series, wont it get cooked? I sure think so. Don't overlook the voltage regulator. If you are using an external regulator this could be the issue. |
Rick,
It would depend on the voltmeter. I have one that will read up to 10 Amps and I doubt if he has that much draw. I don't know about the MSD but on my Jacobs Pro Street module, I can disconnect two wires and move them to another place on the terminal strip and run the car just through the distributor and coil like they bused to, which makes it easy to eliminate the Jacobs as a cause of problems. Ron :) |
I think the battery drain was caused by something else. I've driven it so several times since the incident and haven't had a problem since. It probably won't cut out again until I get her into a heavy traffic condition (stop and go). I did change out the ignition switch as it was cheap and easy. I've also purchased a magnetic pickup for the distributor and will change that out next.
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The voltmenter won't get cooked as it only measures a difference in voltage, not amp dram. It could be a 1000 amp draw and you could measure the voltage potential difference with you $9.95 Harbor Freight VOM meter w/o any fear. (do it every day) |
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