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Thread: An '84 325e with no spark :/

  1. #1
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    An '84 325e with no spark :/

    Hi gang. First E30, first post, first time dealing with no spark.

    I'm a complete amateur with these cars so please bear with me. I've been scouring the internet for information on finding the culprit to the issue. The car has been running like a dream for the past week. And this morning it won't start.

    The car turns over properly, but the plugs won't fire. The reading on the positive post 15 at the ignition coil (brand new) is in the millivolts with the key in the on position and when the engine is turning over.

    I've tested all relays, they checkout. Have yet to pull the cps, which I understand is a variant of the common cps on the non e models.

    I'm really scratching my head here (and on the verge of tears ). I need this car to run by monday and it seems the chance of that happening is slim.

    If there is anyone out there... SOS!

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    Figured it out. Fusible link on the secondary positive lead from the battery was fried. Replaced with an inline fuse holder. Good to go!

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    Well I’m back... the inline 50amp AUG fuse I installed to replace the fusible link won’t stop blowing. To the point that it will just pop right when I put the fuse in, without starting the car. The engine ground is fine, and added a new battery ground strap as the old weave like strap had begun to tear at the battery terminal connector.

    The only thing I’ve changed since owning the car was the stereo. The only precieved issue with the car is a hum coming from the fuel pump as if it’s about to give out (sounds like chickens hooting almost ha)

    If it’s the radio does that mean it has a bad ground?

    If it’s not the radio, what are step by step instructions someone can pass along so I can sniff out the issue? Guessing this has to be a ground issue somewhere in my ignition system as that secondary positive lead operates the coil, switch, DME, and fuel pump (right?). If I’m on the right track here, how would I use a test light to find the issue? Is that even the right tool to use?

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    Another piece of info. When the fuse is in place, and I connect the battery, the fuse will blow out. Does this mean the positive ignition wire is grounding somewhere? Just trying to get his headache to end.

  5. #5
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    It started afyer you swapped the radio? Pull the radio out and see if it pops. That would be my start

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    Quote Originally Posted by superj View Post
    It started afyer you swapped the radio? Pull the radio out and see if it pops. That would be my start
    still have the issue with the radio out. With all of the positive wires removed from the front fire wall post, the fuse still blows. Thinking this could be a bad battery issue, but now I'm just guessing. There's something either magically connected to the battery that is giving it a high loud and shorting the fuse without the car being turned on or the batt (i guess?).

    I've literally bought out the 5 auto zones in my area of their 50A AUG fuses.

  7. #7
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    You are going to have to follow that wire and see where it us rubbing through and shorting out. That is why the fuse is blowing. The rubber\plastic insulation has gotten torn or rubbed by something so the metal wires inside keep touching some metal piece and sending the battery voltage to the metal instead of to your starter.

  8. #8
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    From the trunk, you have the main battery lead and the secondary lead for the engine electronics. The secondary lead is the one with the fusible link. These both lead to a junction block on the firewall. Note that there are two electrically isolated binding posts on the block. Once you look at it, you'll understand what I mean. The main post is connected to the heavy cable and is the one for most of the vehicle electrics. The engine electronics post is connected to the smaller black battery wire and feeds only the engine electronics. Whatever is connected on the secondary post is what's blowing things up. If you've actually disconnected everything from this post and the fuse still pops (I assume as soon as you put it in) somewhere between the trunk and the junction block that wire is shorting out. You're going to have to inspect that wire until you find out where.

    Here's some additional information on the secondary circuit. The reason two separate wires were ran was to isolate the electronics and give it a cleaner power supply. Basically a way to isolate it from spikes in the main electric system. Besides the black supply wire, there should only be two red wires connected to that post. The red wires feed the electronics. If there are any other wires hooked up here, they're likely after-market (amp wire?) and should be moved to the other post. The smaller red wire feeds the fuel pump through it. The larger red wire is all the rest; injectors, ecu, etc. If it turns out the supply wire is completely shot, the replacement cable is BMW PN 12421375601 which includes both conductors. It can be found for about $90. If you run a new wire to replace the secondary conductor, it should be 8 AWG copper or metric 6 mm2 and fused at 50A.
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
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    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
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  9. #9
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    Richard, don, you are the man. You always help with such solid info, I read most everything you post just to learn. Hattip
    1987 325e, coupe, 5speed
    1989 325i, sedan, 5speed

  10. #10
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    Quote Originally Posted by richardodn View Post
    From the trunk, you have the main battery lead and the secondary lead for the engine electronics. The secondary lead is the one with the fusible link. These both lead to a junction block on the firewall. Note that there are two electrically isolated binding posts on the block. Once you look at it, you'll understand what I mean. The main post is connected to the heavy cable and is the one for most of the vehicle electrics. The engine electronics post is connected to the smaller black battery wire and feeds only the engine electronics. Whatever is connected on the secondary post is what's blowing things up. If you've actually disconnected everything from this post and the fuse still pops (I assume as soon as you put it in) somewhere between the trunk and the junction block that wire is shorting out. You're going to have to inspect that wire until you find out where.

    Here's some additional information on the secondary circuit. The reason two separate wires were ran was to isolate the electronics and give it a cleaner power supply. Basically a way to isolate it from spikes in the main electric system. Besides the black supply wire, there should only be two red wires connected to that post. The red wires feed the electronics. If there are any other wires hooked up here, they're likely after-market (amp wire?) and should be moved to the other post. The smaller red wire feeds the fuel pump through it. The larger red wire is all the rest; injectors, ecu, etc. If it turns out the supply wire is completely shot, the replacement cable is BMW PN 12421375601 which includes both conductors. It can be found for about $90. If you run a new wire to replace the secondary conductor, it should be 8 AWG copper or metric 6 mm2 and fused at 50A.
    Thank you for the response, Richard! Yes, I've disconnected everything from the post and the fuse still pops. I've got the passanger seat bench out now and tracing the positive lead through the vehicle. Is there a diagram that shows how the positive cables run through the car? I'm assuming from the seat and down the passenger side trim, through the firewall?

    Dealing with this battery in the trunk just makes me want to move it to the front tray. I know this is a bmw thing but f**k it's annoying, especially with this issue and having to tear out the interior because one wire is shot.

  11. #11
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    http://wedophones.com/BMWManualsLead.htm has the relevant ETM docs. The locations of some components are in there, but not that one. Good luck with everything!
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  12. #12
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    Quote Originally Posted by richardodn View Post
    http://wedophones.com/BMWManualsLead.htm has the relevant ETM docs. The locations of some components are in there, but not that one. Good luck with everything!
    Wow. This is going to be quiet the task. The entire passenger side of the interior has to come out to run the new wire through the vehicle. I actually think I'm going to move the battery to the front tray for the time being so I can have a running car, and save the work for a long weekend. I read elsewhere its possible to do this with all of the parts already in vehicle but the description on connecting the front junction box to the battery is a bit vauge.... Any advice? Here's what I found:

    from this thread: http://www.e30tech.com/forum/showthread.php?t=39677
    To put the battery in the tray in the engine bay, all you need to do is unhook the battery cable from the connector on the firewall and hook it to the + terminal of the battery (once you install the battery in the underhood battery tray). Then unbolt the ground cable from the trunk and hook it to the - terminal of the battery and the other end to a solid ground point (I think there's one on the battery tray- but not sure).

    If I did it as above, how would the ignition system, the secondary positive wire reaming isolated from everything else? I mean, at it's current setup they aren't they both connected to the same positive end of the battery? but I guess this is where my knowledge on wiring and electrical gets a little fuzzy. How can two positive wires remain isolated from each other while connected to the same battery?
    Last edited by eppy; 01-20-2018 at 08:33 PM.

  13. #13
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    Quote Originally Posted by richardodn View Post
    http://wedophones.com/BMWManualsLead.htm has the relevant ETM docs. The locations of some components are in there, but not that one. Good luck with everything!
    Wow. This is going to be quiet the task. The entire passenger side of the interior has to come out to run the new wire through the vehicle. I actually think I'm going to move the battery to the front tray for the time being so I can have a running car, and save the work for a long weekend. I read elsewhere its possible to do this with all of the parts already in vehicle but the description on connecting the front junction box to the battery is a bit vauge.... Any advice? Here's what I found:

    from this thread: http://www.e30tech.com/forum/showthread.php?t=39677
    To put the battery in the tray in the engine bay, all you need to do is unhook the battery cable from the connector on the firewall and hook it to the + terminal of the battery (once you install the battery in the underhood battery tray). Then unbolt the ground cable from the trunk and hook it to the - terminal of the battery and the other end to a solid ground point (I think there's one on the battery tray- but not sure).

    If I did it as above, how would the ignition system, the secondary positive wire reaming isolated from everything else? I mean, at it's current setup they aren't as they're both connected to the save positive end of the battery, but I guess this is where my knowledge on wiring and electrical gets a little fuzzy. How can two positive wires remain isolated from each other while connected to the same battery?

  14. #14
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    Just to be sure, does the fuse blow as soon as it's inserted with the junction block end disconnected?

    He went from front mount to rear mount. IIRC, the front mount cars have a single post junction block while the rear mounts have a two post block. First, I really recommend changing the cable instead of relocating the battery. At the very least, I'd determine where the short was to make sure the main cable is unaffected. However before I relocated the battery, I'd try this. Disconnect the black electronics lead at both ends. Make a 50A fused jumper with 8 AWG wire and jumper the two posts in the block together. It must be fused as there is nothing else protecting the electronics. I don't think BMW used a fuse in the front battery cars, but it won't hurt to have it. I don't think this will affect the electronics, but I make no promises.
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  15. #15
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    Quote Originally Posted by richardodn View Post
    Just to be sure, does the fuse blow as soon as it's inserted with the junction block end disconnected?

    He went from front mount to rear mount. IIRC, the front mount cars have a single post junction block while the rear mounts have a two post block. First, I really recommend changing the cable instead of relocating the battery. At the very least, I'd determine where the short was to make sure the main cable is unaffected. However before I relocated the battery, I'd try this. Disconnect the black electronics lead at both ends. Make a 50A fused jumper with 8 AWG wire and jumper the two posts in the block together. It must be fused as there is nothing else protecting the electronics. I don't think BMW used a fuse in the front battery cars, but it won't hurt to have it. I don't think this will affect the electronics, but I make no promises.
    Yes, the fuse blows when nothing is connected to the junction box. When I replace the fuse, I disconnect the ground, insert the fuse, and then reattach the ground as I don't want to end up with glass in my hand. Right when the ground touches the battery negative, the fuse pops.

    I'll give what you've suggested a shot and see what happens. But yes, I simply don't have the time (right now) to tear out my entire passenger interior to trace the cause of the problem, only to replace the wire and have it potentially happen again...

  16. #16
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    Richard... I did as you explained and voila, it's starting and driving again without blowing the fuse, and all of the electrical seems to be working just fine. Hopefully next weekend I'll be able to take the time to tear out the interior and see where the positive is arcing.

    Here's what the setup looks like at the front junction box.

    IMG_4570.jpg


    And a couple of the car

    IMG_4530.jpg
    IMG_4532.jpg

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    No e30s, again :(
    At least you are driving again.

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    Sweet!
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

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