Oh yes, without a root cause there is no point in declaring it fixed...
Don't let the smoke out!
- Thread starter Honolulu
- Start date
Honolulu
Well-Known Member
Thanks guys, current thinking is that the starter is shorted to ground and eating all the available amps, so the dash indicator lights don't even glow. I'll get the DMM on it and see what is revealed. I think: one meter pin to B+, the other to the block. There should be no voltage between the two. I have to think about this a bit.
Looking at the wiring diagram(s), there are several ground points throughout the car for various groups of electrical consumers, but where is the main ground for the engine?
Looking at the wiring diagram(s), there are several ground points throughout the car for various groups of electrical consumers, but where is the main ground for the engine?
ElGrecko
Well-Known Member
First, disconnect the cable that goes to the starter and tape it up to make sure it isn't grounded. Then turn on the ignition and see if you get voltage on the other circuits and that the other things are working properly.
H> I think: one meter pin to B+, the other to the block. There should be no voltage between the two.
Disconnect the battery, measure ohms between B+ and the chassis ground. If you see zero ohms then there is a short.
Else, repeat with the key moved to RUN, if no short repeat with the key moved to START.
If the short is only during START, disconnect the starter positive, reconnect the battery, and push start the car. At 6 ft 6 I bet you can push start the car as a matter of course.
My battery has a braided copper ground from the battery (-) to the engine bay. There should be another braided copper ground from the chassis to engine/tranny I heard. These can carry the AMPs. The other grounds are toys.
Honolulu
Well-Known Member
Oh, I've push started many a car and my bikes as well. I live 800 feet up a ridge behind Diamond Head. OTOH if the car doesn't start, I'll have to bug my pal for his Tacoma and tow strap.
Now all that's lacking is the mental energy to actually perform the work.
Now all that's lacking is the mental energy to actually perform the work.
Wow, it's a small world, I used to live on Poka St., one street up from Diamond Head Rd. That was a couple of years before I bought my E9 on Maui though.
Have we mentioned if this is an auto or standard? The auto has a relay for the starter.
Honolulu
Well-Known Member
Car is manual, converted from AT to 4-speed, then 5-speed. It worked when parked. I spent a considerable time figuring out the start sequence from the electrical diagrams and I *think* I took out all the wiring made extraneous by the trans swap(s). It ran for years in all three trans situations. Either I got lucky or did it right.. until. Something about the long layup has changed things.
In the face of an immediately upcoming 5-week trip to Munich, I've not gone in after the starter which is my current and only suspect after I verify some wiring and put on a substantial engine ground. R&R of the starter years ago wasn't any fun at all.
In the face of an immediately upcoming 5-week trip to Munich, I've not gone in after the starter which is my current and only suspect after I verify some wiring and put on a substantial engine ground. R&R of the starter years ago wasn't any fun at all.
Kinda sorta...
Voltage is like pressure in pipes, but unlike water, electricity only flows according to a very specific law called Ohm's Law. Here we have V=IR.
If you have a high voltage and a high resistance only a small current will flow. Electrons are not like water behind a dam that will try to make that path a lower resistance (like water would through erosion). They may try to find another path (for example an arc), but if the resistance is high in any circuit, the current will be correspondingly low, and clearly that is not the case here.
I think this issue is more complex than it seems. As @Arde noted, If the B+ wires are burned, then that is where the current was flowing. Now, it is important to rememberer that the B+ wire from the alternator comes directly from the alternator diodes. Current can normally only flow OUT of the alternator to the battery. The alternator itself does not generate any current unless it is spinning, so since the motor was not turning, the current causing the burning wires had to be coming from the battery (there is no other source of current in the car when the motor is not turning), and INTO the alternator (key observation).
If the only source of current is the battery, then the obvious question is, where is the ground that is allowing battery current to go INTO the alternator, and thence to ground?.. There are two possibilities:
1) One or more of the alternator diodes is shorted (somewhat unlikely, because they would more probably fail open)
2) The voltage regulator is shorted and the field coil is being energized without the alternator turning.
The #2 mode is a bit weird.. The BMW voltage regulator is a modular unit that directly senses the battery voltage (i.e., on the internal end of the B+ wire). This then opens or closes a switch that ties the ACC or RUN bus line to the field coil. As I recall the field coil wire is external to the alternator, and thus is not just the B+ line. Now, if the voltage regulator developed a short from the sensing wire (internal) to the field coil wire, then this would allow B+ current to flow from the battery into the regulator, and from there to ground through the field coil, which, when stationary, is pretty much a dead short to ground.... Normally this would not occur for three reasons: a) the regulator is not shorted, b) the unloader relay will disconnect the ACC bus from the circuit when the key is in the START position, and c) the alternator is moving so the reverse EMF in the field coil would not make it look like a dead short...But if the regulator is shorted, all bets are off.
In any case, it seems that the culprit is the alternator. Either shorted diodes or a shorted regulator. Fortunately the regulator can be removed in about 20 seconds, so do that and then carefully apply power to the battery. If nothing happens, then it is the regulator. If it still smokes, then it is the diodes.
Good Luck!!
Scott
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Honolulu
Well-Known Member
Thanks for those thoughts, Scott. Failure of the alternator would seem to be ruled out since O'Reilly got it to work on their tester.
Another thought: just how/where is the engine grounded to the body? Although I've not removed anything (lately) that would seem to have served the purpose of grounding the engine, somehow current is flowing where it shouldn't and I can't see a ground nor recall ever having seen one.
And another: how does one identify an internally regulated alternator? I have some vague recall of having, maybe, changed the alternator at some point.
Another thought: just how/where is the engine grounded to the body? Although I've not removed anything (lately) that would seem to have served the purpose of grounding the engine, somehow current is flowing where it shouldn't and I can't see a ground nor recall ever having seen one.
And another: how does one identify an internally regulated alternator? I have some vague recall of having, maybe, changed the alternator at some point.
restart
Well-Known Member
I think…. An old style alternator with an external regulator has a 3 wire plug, similar to a headlight plug.
A newer internal regulator alternator only has 2 wires.
I’m like ai though. Sometimes wrong.
A newer internal regulator alternator only has 2 wires.
I’m like ai though. Sometimes wrong.
Another thought: just how/where is the engine grounded to the body? Although I've not removed anything (lately) that would seem to have served the purpose of grounding the engine, somehow current is flowing where it shouldn't and I can't see a ground nor recall ever having seen one.
Braided cable at firewall to #6 cylinder area of engine. About 6” long.
When bad or disconnected your throttle linkage will get hot and spark at the throttle body as it becomes the engine ground
Braided cable at firewall to #6 cylinder area of engine. About 6” long.
When bad or disconnected your throttle linkage will get hot and spark at the throttle body as it becomes the engine ground
I think we go back to the question of the burned alternator wire. If that is the primary DC wire (and not the field wire) then, with the engine not turning, there is no reason that wire should conduct. It leads directly to a set of diodes all of which are blocking any current INTO the alternator. The engine was not turning, so the alternator was not generating any current, so somehow that wire is leading to a short, either inside the alternator, or some mechanical short to the alternator body and thence to ground.
I am not sure I'd necessarily trust some dude at O'Reilly to confirm the operation of the alternator either. The test they perform may not address the issue you are having.
Can you trace the burned wiring? Where did it start?
My guess, and you probably won't like this, is that you hooked up the jumper cables backwards. The ONLY source of current was your jumper battery, and the only way that current could go into the alternator (if it is somehow not internally shorted) is if the alternator diodes were forward biased. The only way that could happen is if the jumper battery was hooked up backwards.
Below is a typical alternator. You can see the three diodes (the arrow-like things) on the right. The terminal marked "Battery Terminal" is the wires you say are melted. Current can only flow in the direction of the diode arrows, which is to say it cannot flow INTO the alternator. If the battery was hooked up backwards then you can see that current would flow directly from ground through the diodes and back to the battery.
This is also supported by the fact that you say there were no dash lights or any thing in the car when you tried to start it with the jumper battery hooked up. There would not be because everything was powered backwards. I'd disconnect the alternator wires, tape them up and re-attach the jumper battery, being certain it is connected the right way, and try the starter... The car will run without the alternator (for a while), and that should tell you if there's any permanent damage (I'll bet your alternator got pretty hot, so it might be worth $300 to swap it out).
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Honolulu
Well-Known Member
I thought that I could have put the jumper wires backwards but I like to think I'm not THAT careless. The "only source of current" noted above is the key (maybe). I also question the starter, which was getting reluctant to turn the engine. It would work fine after several attempts with the key, just not on the first try. I'll look at the electrical portion of the ignition switch first, then bang on the starter in case it's stuck. I had it out years ago; the solenoid seemed to work but (I think) internal grunge prevented the solenoid from switching current to the starter as it should have. Obviously there is no lack of suspects, but I tend to overthink things I don't fully comprehend.
As for the O'Reilly test, I saw the alternator being spun on their tester and though I didn't have time to study what they did, it seemed okay.
Thank you Don. I'm pretty sure the braided cable ground at the back of the engine is long gone missing. I have some vague, decades-old recollection about it, but I'll have to look again, and replace if indeed it's missing, possibly in a more conspicuous location. The battery tray is pretty rusted out, so there's an opportunity to do the "cool" thing and put the battery in the trunk though I am dubious about the path of new cables and their minimum gage. Some forum searching by me is appropriate.
If only there was another E3 or E9 hereabouts, but I've not seen either for years now.
As for the O'Reilly test, I saw the alternator being spun on their tester and though I didn't have time to study what they did, it seemed okay.
Thank you Don. I'm pretty sure the braided cable ground at the back of the engine is long gone missing. I have some vague, decades-old recollection about it, but I'll have to look again, and replace if indeed it's missing, possibly in a more conspicuous location. The battery tray is pretty rusted out, so there's an opportunity to do the "cool" thing and put the battery in the trunk though I am dubious about the path of new cables and their minimum gage. Some forum searching by me is appropriate.
If only there was another E3 or E9 hereabouts, but I've not seen either for years now.
There is a beauty on Maui that I finished a few years ago. Upcountry in Makawao…
I got my car from a man in Kula 12 years ago and I met a man in Kihei who runs Sugar Beach Events who had a nice one. That's all I've ever seen on Maui.
Can you trace the wires, so we know what is where?
1) Did you have the old battery in the circuit (presumably yes)?
2) Does the ground from the (old) battery go directly to the body?
3) Does the large positive wire go directly to the starter, or does it go to the alternator and then to the starter? (there are three ways this might be done: a) battery to starter to alternator; b) battery to alternator to starter; c) separate wires battery to starter and battery to alternator).
Your jammed starter theory may be correct, but only if the wiring travels from the battery to the alternator and then to the starter. In that circuit, the heavy current would flow from the battery to the alternator and then over a fatter wire from the alternator to the starter. If the starter was jammed it would draw significant current, and the smaller alternator wire would melt before the larger starter wire.
Can you also inspect the wires carefully to see if there is any rodent damage to the insulation? Not sure what critters you have in Hawaii, but rats and mice often gnaw on wiring, and either break the wires or expose the writing through the insulation, especially if the car has been sitting a while.
Can you disconnect the wires from the alternator, and try jumping it again? It should run on the jump battery with the alternator disconnected.
I'd hold off on moving your battery. Fix this issue first, and consider that moving it (which I know many others have done) is pretty involved. You have to run some large wires all the way forward from the trunk to the engine bay. Easy for a bodge job, but much harder to do right.
1) Did you have the old battery in the circuit (presumably yes)?
2) Does the ground from the (old) battery go directly to the body?
3) Does the large positive wire go directly to the starter, or does it go to the alternator and then to the starter? (there are three ways this might be done: a) battery to starter to alternator; b) battery to alternator to starter; c) separate wires battery to starter and battery to alternator).
Your jammed starter theory may be correct, but only if the wiring travels from the battery to the alternator and then to the starter. In that circuit, the heavy current would flow from the battery to the alternator and then over a fatter wire from the alternator to the starter. If the starter was jammed it would draw significant current, and the smaller alternator wire would melt before the larger starter wire.
Can you also inspect the wires carefully to see if there is any rodent damage to the insulation? Not sure what critters you have in Hawaii, but rats and mice often gnaw on wiring, and either break the wires or expose the writing through the insulation, especially if the car has been sitting a while.
Can you disconnect the wires from the alternator, and try jumping it again? It should run on the jump battery with the alternator disconnected.
I'd hold off on moving your battery. Fix this issue first, and consider that moving it (which I know many others have done) is pretty involved. You have to run some large wires all the way forward from the trunk to the engine bay. Easy for a bodge job, but much harder to do right.
Sugar Beach was Don Nelson’s car
Josh has the one in Makawao
Hi Charlie - It sounds similar to my car after I installed the rebuilt engine and tried to start it without the 6 inch braided copper engine grounding strap connecting the bell housing bolt on back of the engine above the starter, nearest the firewall to the firewall. To run the car before I got the proper grounding strap, I used a makeshift spare battery terminal cable between one of the intake manifold bolts and the firewall. Good luck - Dave