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Thread: 1987 mgm battery size, diagnosing and fixing no crank

  1. #1

    Default 1987 mgm battery size, diagnosing and fixing no crank

    The 1987 MGM suddenly won't crank, and won't click the solenoid. Jumping with cables produces no change. So I pulled the battery.
    One store reports the battery at 12.6 volts, 89% charged, but bad, won't take a charge, needs a replacement. The current battery is size 24. They recommend size 56. Another store says direct replacement is 64.
    Suggestions?

  2. #2
    Member WagonMan's Avatar
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    Group 56 is the standard battery with small alternator. 64 is for heavy duty (police package) with 100 amp alternator. Cars with the heated windshield also came with a group 64 battery.
    1990 Colony Park
    1970 HEMI Superbird

  3. #3

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    The 2nd store tested and reported good battery. They charged it, and tested it the next day. I installed and tested with the lights, dash lights run, and clock, all ok. A crank attempt killed all other electrics, which returned sometime afterward. If I had to guess, I thinking a short in the starter or solenoid that reduces voltage too. Suggestions?

  4. #4
    GMN = life johnunit's Avatar
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    the crank cutting things out is a breaker going, usually caused by a bad connection. Take a file, or some emery cloth to every connection near the battery, especially around the starter solenoid on the fender.

    85 4 door 351 Civi Crown Victoria - Summer daily driver, sleeper in the making, and wildly inappropriate autocross machine
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    06 Mazda 3 hatch 2.3L 5AT (winter beater that cost more than my summer car)

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    Member BigT's Avatar
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    I upgraded to a more powerfull battery, but I don't remember the group number. I can get it after work. I also picked one with the POS and NEG reversed. I didn't like the idea of the POS side so close the the fender/ground.




    I'd rather be a failure at something I love than a success at something I hate.
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  6. #6
    Southern
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    65 series battery works on an 88 or newer model from the factory. Heck the 2011s use s 65 series.

    I put a 65 series in my 87, it works just fine. The hold down well...that doesn't hold any more.
    -Nick M.
    Columbia, SC

    66 Squire, 89 Colony Park, 90 TC, 03 (2x) TC, 06 TC, 07 TC
    03 BMW 540iT, 05 GMC Yukon (tahoe)

  7. #7

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    Bobby has a "65" in his 87 GM. He used a dremel to trim down the "ridge" in the battery support and all is well. There is no hold down but the battery is so heavy and wedged in well so there has not been a problem.

  8. #8
    GMN Regular DerekTheGreat's Avatar
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    Seems to me functional hold downs are unobtainium. I never see those at yards.
    1985 LTD Crown Victoria - SOLD
    1988 Town Car Signature - Current Party Barge

  9. #9

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    There are generic ones but not sure how good they are.

  10. #10
    Beater gonna beat sly's Avatar
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    I use some in between size in the 88 since the hold downs were crap in that one and I just put in a generic battery tray and J hooks.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 88 MGM (SOLD), 93 Vic, 2000 Crown Vic, 2003 Expedition
    Quote Originally Posted by gadget73
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  11. #11
    I post a lot...
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    You may have bad battery clamps lose conections.

  12. #12
    Member BigT's Avatar
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    I bought a 34. It has 800 cold cranking amps. It's an AutoCraft from Advanced Auto.




    I'd rather be a failure at something I love than a success at something I hate.
    George Burns

  13. #13

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    John, after ignition switch > run, I jumped the solenoid with a screwdriver, and got a small spark, no crank, and all other electrics stopped. After removing the battery negative terminal, waiting a few hours, and reconnecting the neg. terminal, electrics are ok, until I tried a switch > start, and the change was some clicking, along with no crank, and dead electrics. Where would I find a breaker that might be tripping and then eventually resetting?

  14. #14
    Beater gonna beat sly's Avatar
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    that sounds like weak battery to me. If the terminals are on the battery good and tight, I'd suspect the battery at this point. The other problem could be bad terminals or bad contact to the frame/starter.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 88 MGM (SOLD), 93 Vic, 2000 Crown Vic, 2003 Expedition
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  15. #15

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    I'm trying again to crank. The battery has been replaced with this one for $105 plus tax:
    AutoCraft Silver Battery, Group Size 56, 550 CCA
    56-1 Warranty: 2 YR FREE REPLACEMENT

    A start try immediately trips a circuit breaker, that resets after I disconnect and reconnect the battery negative terminal. My voltmeter died, so I'll get one tomorrow, disconnect the fat starter cable from the relay, and see if I get 12 volts at the relay output terminal when my associate tries the ignition > start. If so, does that indicate a possible short in the solenoid, starter or its cable? If the circuit breaker trips upon switch > start with no grounding from the relay output, does that point to a short in the ignition > neutral > relay input circuit?

  16. #16
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    have you wacked the starter?
    "X" car 89 Colony Park LS Mods>Engine delete, SS duals magnaflow hflow cats, 2010 Must GT mufflers, auto air shocks, Posi, Tran cooler, big front brakes, 03+ rear disks, Large 3g alt, Tripminder, GS grill, 86 seats, 16" HPP wheels, winter boots=96 Cartier wheels, 215-65/16 Goodyear ULTRA GW3 snows, pi rear sway, alum driveshaft.
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  17. #17

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    The starter whack is the first thing to try after someone with a jack and jack stands gets here. I don't have many tools at this location, and the first two mobile mechanics haven't called back or have a non-working phone number.

  18. #18
    Member EaOutlaw1969's Avatar
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    Let me see if I got this in my head correct, The car started and ran fine until one day you went out to start the car way back in October of 2015 then it just would not crank the engine over. Is this correct?

    And now finally after all this time you bought a battery, installed it and now you have the same symptom?

    Am I on board with what has happened to date?

    Has anything else at all been done with this car to prepare it for long term storage?

    Has any of the work suggested by other members in the past been completed like cleaning the battery cables ends at the battery and at the starter plus solenoid?

    This car has been sitting for 4 years now which has given plenty of time for the fuel to become stale even with fuel stabilizer in it. Same goes with the engine oil and other fluids they all need to get changed.

    If I were you I would start with the basics, First check with a large ratchet and socket at the crankshaft and make sure the engine spins over by hand after pulling the spark plugs and adding a little marvel mystery oil or hell any oil at this point to each cylinder make sure it rotates two full rotations in the normal direction of rotation.

    Then disable the fuel pump by tripping the inertia switch or unplugging it.

    Clean the battery cable connections at the battery at the starter solenoid and starter if the terminal ends are not original remove them from the cables and inspect the cables for corrosion, if the wiring has corrosion replace the battery cables. ( make sure to remove all the grounds check the connections clean and or replace as needed)

    There is no magic circuit breaker that is tripping and resetting so get that notion out of your head. ( this is not complicated )

    Once you have known good power and ground connections at every point mentioned with the key off go ahead and remove the ignition switch wire at the the starter solenoid and run a jumper wire from battery positive to the small stud on the solenoid and lightly touch the jumper wire to that stud. The starter should crank for as long as you hold the jumper wire to the starter.

    If it the starter does not spin over you could have a bad solenoid or starter or both could be bad. They are both cheap enough to just replace them with good quality parts. Or you could continue to diagnose it if you have a DVOM and amp meter. A volt meter alone will only tell you part of what may be wrong meaning you could check and find the needed voltage at the starter but not the amperage.

    Which is why I think it would be best just to replace both the starter and solenoid if cleaning the connections do not help. I say this for a few reasons the age and time these parts have been sitting not working.

    I suggested disabling the fuel pump because if your fuel is 4 years old you will at minimum want to drain and flush the tank, replace the filter flush the fuel lines before just sending that crap to your injectors regulator etc and causing more problems ( which may already need work because of age and sitting )

    I am not sure how long it takes before your fuel will turn from a varnish to a molten tar like substance but I would say with today's fuel it is safe to say it is not looking promising for the fuel delivery system.
    2007 Ford Crown Victoria LX Sport

  19. #19

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    EA, thanks for the detailed plan. You have a good picture of my neglect of the car. If I can get someone to show up with a plug wrench, a breaker bar, and crank socket, we can pull the plugs, pour in some MM oil, and turn the engine. How about letting the MM sit for a day, rotate 1/2, add more MM, let it sit, and rotate 1 1/2 or so? Where's the fuel pump inertia switch and/or relay? When I get a hold of a jack and stands, I can check the connections at the starter. When the multimeter worked the resistance from the fat cable off of the relay to ground at the battery was only an ohm or two. Is that normal or indicative of a short? If the voltage drop from the battery to the relay output, with the cable off of it, is less than about 0.8 volts, does that point towards adequate available amperage at that location, and a functioning relay, neutral cut out, and ignition switch? What might cause the interior lights to go out immediately after the start attempt at the ignition switch, and then come back on after disconnecting and reconnecting the negative battery terminal?
    Thanks again for your help.

  20. #20
    Member EaOutlaw1969's Avatar
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    First things first and most important, Keep this problem simple and do one thing at a time. and please do not over think it with voltage drops and specifics without the correct tools knowledge manuals etc you will just end up chasing your tail.

    The inertia switch is normally mounted in the trunk on the right possibly left inside quarter panel behind the carpeting I do not remember where for sure on your car. A quick YouTube or google search may help. once located you will see a red button that will be pushed in you can smack the metal near or at the switch with a rubber mallet or something to cause the switch to trip you will see the red plunger pop up and stay up. just push the button back down when your ready to activate the pump again.

    As far as pulling the plugs and adding a little ( about 1 ounce per cylinder is all that should be needed ) and yes let it sit before rotating longer the better.

    A few reasons I suggested pulling the plugs and adding oil to each cylinder then trying to rotate the engine by hand. First I do not know if your engine stopped running and or cranking from a mechanical failure, unknown overheating issue, bearing, oil pump failure etc that could have locked up the engine. ( Why try and diagnose a starter battery wires if you have a shot engine ) .

    Second it has been sitting so long adding a little MM oil will help lubricate the cylinder walls and rings which will hopefully bring up the compression and possibly free up any rings that may be stuck to the pistons.

    Since the car has been sitting and there is a possibility of critters getting into places where they should be make sure to pull the air cleaner and check the filter is clean and housing is free of debris and rats nest etc.

    Make sure to label each plug wire so you do not cross wire the engine when you put it back together.

    If and when you get the engine cranking over you will need to have towels in place over the plug holes and below to collect the oil that gets shot out during cranking, and you will want to crank the engine over long enough in short burst to get most of the oil out.

    A couple cans of non flammable brake clean once the plugs are put back in will help clean up any oil that got on the exhaust.

    If you cannot stand it and just want to get technical and want to test something with a DVOM make sure your new battery is fully charged and really is in good working order and not NEW meaning ( never ever works )

    BTW the lights coming on then going out after a crank attempt then coming back after waiting tells me you have bad connections.

    Since tools, manuals,money and time may be an issue, again lets keep this simple and try not to waste any of it.
    Cleaning and inspecting all the cables terminals ends etc should really cost you nothing, at minimum you will need a wire brush and or battery terminal cleaner tool, possibly some sand paper to clean off ground contacts on the block and frame body etc.

    Whatever you do do not just look at a connector and say hey that looks good and move on to the next without removing each connection one by one and wire brush sand etc each connection. take pictures mark wires etc to make sure you get everything back together properly especially at the solenoid, do one connection at a time to avoid confusion. there are not that many wires but there is enough that you could get them confused when reassembling them if you removed them all at once.

    BTW you should have factory fusible links at the starter solenoid that feed power to different parts of the car once you get the wiring connections cleaned up at the solenoid feel these links by grabbing them with your fingers with both hands and give them a genital tug, corrosion can and will eat away at these links causing all sorts of issues where the only thing holding the link together is the corrosion and a strand or two of eaten wire if severely corroded the insulation will stretch and the what is left of the wire strands will snap making it known and obvious these links must be replaced.

    Even if they look good and feel good with nice freshly cleaned connections with a razor and carefully shave a little of the insulation trying not to hurt the strands of wire and see if the wire strands are corroded if they are in good shape just tape up the inspected area with some good electrical tape. if they are shot solder in good replacements but make sure to replace the entire link at the factory splice or further down line slightly if need to get to fresh non corroded wire.
    2007 Ford Crown Victoria LX Sport

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