Car wont start w/ red and black wire connected ('80 528i)

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brotherhay
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Car wont start w/ red and black wire connected ('80 528i)

Post by brotherhay »

Im back for more BMW abuse, and once again were back to starting issues. Ive still got to track why the battery drains, but first I have to get a little help to figure this one out.

Car wouldnt start (1980 528i). Took the starter out, bench tested it, nothing. Well thats easy enough, new starter installed, everything connected, still wouldnt start.

I read a few posts here, and wanted to double check the wiring thats connected to the solenoid. The large post wires are easy to figure out, they go to the only usable post. But its the smaller ones that seem to trip me up. I always figured its the red/black one to the upper post, and the yellow/black to the lower post. I checked it, and checked it again, thats how its wired. The starter will just not engage.

I decide Im going to replace the spades on each wire to be sure they make a good connection. I pull off the top wire, get a bit distracted, and eventually come back and try and start the car again. It starts! I then remembered oh, that lower red/black wire was disconnected. I checked, sure enough its disconnected. Shut the car off, turned it over again, fires right up.

So, what gives? With the yellow/black on, starts fine. With the red/black also connected, it doesnt do anything. I chased the red/black wire over to what looks to be a resistor set possibly? Not sure, but its mounted on the front right side engine compartment. The top rubber connector on that is a little crunchy, looks like it got hot at some point.
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Lock
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Post by Lock »

I'm not 100% on all the wiring, but I can tell you red/black is a bypass supply line to the ignition coil, to supply full 12v when starting to bypass the coil resistor for a better spark (normally it gets 9v via the resistors). The black/yellow I assume is the starter trigger to the starter motor, giving it + when you turn the key (anyone know?)
Maybe your coil resistors are fried/miswired and when the red/black is plugged in, when you turn the key the power for the starter motor is instead going straight to the resistors? This circuit is not crucial but does help when starting.
1979 528i - M30B34 with 9.5:1 B35 pistons, 5-speed conversion G260/6, e28 rear subframe, e34 LSD 3.9:1, glass sunroof, e30 elec speedo, cruise control
brotherhay
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Post by brotherhay »

I did a bit of research looking for a ballast resistor for this car and cannot find one anywhere.

Any suggestions?
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RonDwyer
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Post by RonDwyer »

Try maxmillian, 002 Salvage, Pelican Parts. Dont buy them used.
Ron Dwyer
Milwaukee, Wi

14 Audi A8L TDI
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brotherhay
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Re: Car wont start w/ red and black wire connected ('80 528i)

Post by brotherhay »

lets get this one bumped back up.

Found a new Ballast Resistor. Theres a guy on ebay in Germany that has a bunch of NOS ballast resistors, $60.

Anyway, after installing the new resistor, same thing. If I have the red wired hooked up, the car will start. When it starts you can tell its not going through the resistor since it really makes an awful sound immediately after startup.

While the car is actually running, if I try to hook up the Black/Red wire to the starter, the car actually stalls out.

Am I trying to connect this Black/Red wire to correct place? It looks like its connecting to the top of the Starter Solenoid. There are two posts there, both look to lead to the same connection.

Or, the connections to the Ballast resistor pretty much cooked. The rubber around the connectors have pretty much melted. I suspect I should at least crimp on new connectors to ensure a good connection there.
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Mike W.
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Re: Car wont start w/ red and black wire connected ('80 528i)

Post by Mike W. »

Time to break out the meter. The Bk/Rd should not be connected to anything, electrically speaking, on the starter side except with it cranking. Here's a scan from the BMW factory manual, a little hard to see so you might have to copy it and enlarge it, but you can see where it's connected and verify all connections.

Image
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
brotherhay
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Re: Car wont start w/ red and black wire connected ('80 528i)

Post by brotherhay »

Image

Looks like from the starter is a BK RD that runs to the top of the Ballast Resistor. The ballast resistor splits to the ignition control, and also a BK RD wire from the bottom of the ballast resistor to the Ignition Coil.

checked continuity on both BK RD wires, all check out.

Checked ohms on the ignition coil. .5 ohms at the Primary, 9240 at the secondary.

Not sure what the ohms should be for that coil, but that seems about right.
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Lock
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Re: Car wont start w/ red and black wire connected ('80 528i)

Post by Lock »

Coil resistance sounds normal, that's about what mine has.
Check the BK RD wire for a short circuit to ground. From what you're saying it sounds like somewhere along its length it's hitting negative, so when it's plugged in and you try and start the car, the power for the starter is going via that wire and some resistance to ground, so the starter isn't getting enough power to engage the solenoid.
Try running a new wire in its place from the starter to the top of the ballast resistor and see if the car starts fine.
If this line is giving you too much trouble, also remember that like the cold start injector you don't need it unless you're regularly starting the car in snow.
1979 528i - M30B34 with 9.5:1 B35 pistons, 5-speed conversion G260/6, e28 rear subframe, e34 LSD 3.9:1, glass sunroof, e30 elec speedo, cruise control
brotherhay
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Re: Car wont start w/ red and black wire connected ('80 528i)

Post by brotherhay »

So I think I might know whats up here. The BK RD wire that connects to the Starter Solenoid, its connected to the ground section....
The wire is only long enough to connect to that section, as if its only supposed to connect there.

But from what youve just said, It sounds like this one needs to be connected to the positive terminal huh.
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Mike W.
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Re: Car wont start w/ red and black wire connected ('80 528i)

Post by Mike W. »

brotherhay wrote: Sun May 27, 2018 2:18 pm So I think I might know whats up here. The BK RD wire that connects to the Starter Solenoid, its connected to the ground section....
OK, that's your problem, you're grounding out the coil so it's dying.
But from what youve just said, It sounds like this one needs to be connected to the positive terminal huh.
Not the positive per say, it should go hot when the starter is engaged and only when the starter is engaged. Not all starters have the same wiring and connections, I've seen some without the small push on terminal which is where the red/bk should go. I've seen some with extras. Some with all 1/4" terminals.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
brotherhay
Posts: 66
Joined: Fri Apr 17, 2009 11:40 am

Re: Car wont start w/ red and black wire connected ('80 528i)

Post by brotherhay »

the starter is aftermarket, but I dont think it would have any odd connections.

There are a few spade connectors on the positive side, I figured it probably didnt matter much as to which to connect to.

Gave that a shot, and it did start right away, but still sounded like the started stays engaged too long.

Now when I take that wire off and start it, it does sound fine, not like it previously did, kind of odd.

I can test the connections on the solenoid and see what each does.
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Mike W.
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Re: Car wont start w/ red and black wire connected ('80 528i)

Post by Mike W. »

brotherhay wrote: Sun May 27, 2018 3:11 pm

Gave that a shot, and it did start right away, but still sounded like the started stays engaged too long.
Just as a WAG it could have been backfeeding from the coil/ignition.
I can test the connections on the solenoid and see what each does.
Even that is tricky, the wiring diagram shows the Rd/Bk only being energized when the starter is engaged.

Only reason I know as much as I do about it is from when I put L jet on an old Bavaria and got a wire to the starter in the wrong place. Different problem, it ran, but pig rich, but it all had to do with those wires on the solenoid.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
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