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Thread: No start after 3g Swap...

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  1. #1

    Default No start after 3g Swap...

    So, I thought it would be a fun evening project to do a 130 amp 3g swap on my 87 MGM, I was wrong. I have it wired up as is described in all the places I can find, "self sensing" and not using the original charge wires. What can I remove from the starter solenoid?

    My car will now crank but not start, acts the exact same way if I hook up the old charge cables and before I made it "self sensing" by looping the yellow wire over to the output from the alternator. I would say it's the solenoid, but it wouldn't crank, or would continuously crank if it was bad. No act correctly.

    I will say that it is cranking very slow which is likely the whole issue. Even with the same battery, that I had been using to daily drive the car, fully charged and with the battery charger hooked up to it on "engine start" which is a 100 amp boost in this case.

    Why is this? It does appear someone has moved the battery ground wire from it's original position, which I would like to fix, but need to know how it was routed before to do so.

  2. #2
    I'm an air-conditioned gypsy gadget73's Avatar
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    If the battery is too low to power the ECM while the engine cranks, it might do this. Try to jump it and see what you get. Crusty connections at the starter relay will cause problems, so will bad battery cables, bad connections on the ground side down at the block, and crusty connections on either end of the starter cable. I had a lot of issues with the ground connection on mine. The aftermarket cables have steel ends and they can corrode inside the crimp connection. I replaced it with a cable that had copper ends and the problem went away. I also took the gasket grinder and polished up the block and the bolt before putting it all back together with a wipe of grease on all the surfaces to keep it from getting crusty again.

    There are several grounds, so need to know which one you're talking about and where it currently is.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  3. #3

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    Quote Originally Posted by gadget73 View Post
    If the battery is too low to power the ECM while the engine cranks, it might do this. Try to jump it and see what you get. Crusty connections at the starter relay will cause problems, so will bad battery cables, bad connections on the ground side down at the block, and crusty connections on either end of the starter cable. I had a lot of issues with the ground connection on mine. The aftermarket cables have steel ends and they can corrode inside the crimp connection. I replaced it with a cable that had copper ends and the problem went away. I also took the gasket grinder and polished up the block and the bolt before putting it all back together with a wipe of grease on all the surfaces to keep it from getting crusty again.

    There are several grounds, so need to know which one you're talking about and where it currently is.
    Um, not sure. It appears there are three grounds, and I know the one that goes to the block it wrong as it goes to the bracket that the AC hangs on.
    One goes to the front of that car, and the other looks like it has a fuse looking thing in it and goes back into a harness.

    I hate when people just hack up wires in cars, at the alternator it was duct taped up where the alternator had been replaced within the past two years. I just wanted the 3g, especially since I might be upping my subwoofer game in the future and the current one can dim the lights at louder volumes.

    If I make it by the shop tonight after working my part time job I'll take pictures. Meant to while I was there on my lunch break...

  4. #4
    GMN Regular DerekTheGreat's Avatar
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    FWIW: I used a charge cable from a 90's Conti, routed from the SS along the core support and up the driver's side frame rail to the alternator. I reused the factory charge cables too, because like you, I did not want wires just hanging there nor did I want to hack them out. You can reuse the old cables if you've also got another charge cable, you've given the current multiple options to get to the same place, thus reducing heat from electron flow. I've put over 30k miles on my Town Car since then over multiple years with no issues resulting from the swap.

    About that subwoof game: You'll definitely notice more and punchier, tighter bass output from the upgrade. But, you'll still see the lights wince pretty badly. You can pretty much mitigate that wince by 80% or so by installing a 2uF capacitor close to the amplifier like I did. Some people even recommend installing them (smaller of course) for the ECM and headlights themselves. I was satisfied by just the one near the amp. A 1uF was recommended, but glad I went for the 2. For future installations (Doubtful, home audio greatness has wrecked me for car audio) I'd be tempted to go even larger.
    Last edited by DerekTheGreat; 03-03-2021 at 09:46 AM.
    1985 LTD Crown Victoria - SOLD
    1988 Town Car Signature - Current Party Barge

  5. #5

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    Quote Originally Posted by DerekTheGreat View Post
    FWIW: I used a charge cable from a 90's Conti, routed from the SS along the core support and up the driver's side frame rail to the alternator. I reused the factory charge cables too, because like you, I did not want wires just hanging there nor did I want to hack them out. You can reuse the old cables if you've also got another charge cable, you've given the current multiple options to get to the same place, thus reducing heat from electron flow. I've put over 30k miles on my Town Car since then over multiple years with no issues resulting from the swap.

    About that subwoof game: You'll definitely notice more and punchier, tighter bass output from the upgrade. But, you'll still see the lights wince pretty badly. You can pretty much mitigate that wince by 80% or so by installing a 2uF capacitor close to the amplifier like I did. Some people even recommend installing them (smaller of course) for the ECM and headlights themselves. I was satisfied by just the one near the amp. A 1uF was recommended, but glad I went for the 2. For future installations (Doubtful, home audio greatness has wrecked me for car audio) I'd be tempted to go even larger.
    I'll have the engine bay torn down when the car gets paint and a H.O. swap/mild build this Spring or Summer. So I don't mind the extra wires hanging right now, As I'd be able to gracefully remove them later. It would be my preference to not use them, since the previous owner already hacked them up to replace the 2g alternator that was in it when it went bad a year or so before I bought the car.
    Why the PO didn't just unplug it and plug the new one in? I don't know, but probably had a lot to do with the duct taped juwst twisted together charge wires too.

  6. #6
    I'm an air-conditioned gypsy gadget73's Avatar
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    The later factory ground cable has a fat wire down to the block, a smaller wire that goes to the rad support, and a teeny wire for the ECM ground. Thats the one with the connector that kind of looks like a fuse. Fat cable lands on the block down around the core plugs, forward of the motor mount but not by much. If you get under the car and look in the space between the crossmember and crank pulley, you should find a spot where a bolt can go. That'll be the original spot.

    If its currently on the AC bracket, that can theoretically work but it relies on good connections between the brackets and block, and I wouldn't trust that to be so unless they have been apart and cleaned. I actually once caused the charging system on my car to totally shut down by painting the brackets. Apparently I did such a good job that the alternator did not ground at all. Had to pull it and hit the alt bracket with the gasket grinder where the alternator contacted the bracket and where the bolt contacted.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  7. #7

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    Quote Originally Posted by gadget73 View Post
    The later factory ground cable has a fat wire down to the block, a smaller wire that goes to the rad support, and a teeny wire for the ECM ground. Thats the one with the connector that kind of looks like a fuse. Fat cable lands on the block down around the core plugs, forward of the motor mount but not by much. If you get under the car and look in the space between the crossmember and crank pulley, you should find a spot where a bolt can go. That'll be the original spot.

    If its currently on the AC bracket, that can theoretically work but it relies on good connections between the brackets and block, and I wouldn't trust that to be so unless they have been apart and cleaned. I actually once caused the charging system on my car to totally shut down by painting the brackets. Apparently I did such a good job that the alternator did not ground at all. Had to pull it and hit the alt bracket with the gasket grinder where the alternator contacted the bracket and where the bolt contacted.
    It had been working fine, but I feel it was only put there due to laziness by the PO. It had been working fine up to this point.
    I bet the ECU is no longer grounding properly, either that or the small one to the radiator support. Which, both had been cut off and just shoved in against the negative battery post, which I knew was wrong when I swapped the battery that was in the car for a better one when I got the car. I will be honest, I painstakingly chose to put them back how they were and ignore them until I got around to chasing down all the gremlins in the electrical system.

    If it's known, what wire can I remove from the solenoid post? Mostly because I don't want extra stuff hooked up to cause more potential issues down the road. Like, can I leave just the new 4ga charge wire and the batter wire on and call it a day?

  8. #8
    I'm an air-conditioned gypsy gadget73's Avatar
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    have to fish around to see which fuse link splits into a pair of black/orange wires. Thats the original alternator charge cable. Should be able to remove that one. The rest need to stay since thats the power feeds to the fusebox and such.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  9. #9

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    So, it looks like it was a combination of a bad ground, an old battery, and me having unhooked the wrong set of two cables.

    Currently have the old charge cables hooked up in tandem with the new, I'll get to sorting that out later on.

    Thank you to everyone for the help!

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