1981 633 Wiring questions

[Hefeweizen]

Got a couple of questions where I could not find the answer to.
1. On the ignition coil, I have a black/red and a black wire. which one goes to positive and which one to negative? I'd think that the black goes to negative?

2. The green wire on the distributor, is that supposed to carry any current at all and if how many volts?

Still trying to get that car going. I have fuel but no spark.

[GRNSHRK]

I'll take a look tonight Rainer, as I am in the process of performing an electrical tuneup as we speak

IIRC, that green wire has been a mystery to me as well

But I'll get you the +/- info on the coil for sure

[Ralph in Socal]

Isn't the Green wire from the old points system Condenser? Typical of many german cars of the era. I've seen them cut off on many Mercedes cars.


Ralph

[GRNSHRK]

...it may serve a similar function

Starting in 1980 (I think...) the dizzy has that inductive pickup deal and had done away with traditional points, thankfully

I lost the little U-shaped clip that retains the connector on the green wire, but it's never fallen out of the dizzy so I have no idea if it would run without it or not

Again, I'll be poking around tonight, amidst cleaning spark plugs and whatnot

[Hefeweizen]

Thank you guys for your input so far. I was trying earlier to do the remote start via the diagnostic plug but there was nothing going at all. If anyone could please also tell me how to jump the relays in case I need to do that. For starters (no pun intended) I think I get a new coil.

[cgswift]

Rainer,
You have probably already seen this; it's from an '83. http://shark.armchair.mb.ca/~dave/BMW/e24/e24_83.pdf
This shows a green wire from the ignition switch going to the primary side of the coil. Hope that this helps! Toph

[baders]

Now I'm not sure it is the same, but the 1983 ETM shows the green wire as ignition switch to coil primary at terminal 15. The black wire is the timing control from Motronic. I don't see a black/red wire ?

[Brucey]

FWIW some early cars (eg 1979/1980 models with L-jet) have a three-wire coil arrangement. Typically the blk connection is coil -ve (goes to an ignition control module) and there are two connections to the coil +ve terminal.

The green wire is typically connected via a ballast resistor (and is hot in crank and run) and the blk/red wire is connected to the starter motor so that it feeds ~+12V on cranking straight to the coil.

Presumably if the coil is no longer the original then it could have been replaced by a non-ballasted version, or something. You need to check the pn's carefully.

Do bear in mind that the cold start injector will provide fuel on cranking even if the rest of the EFI system is completely knackered.

On L-jet the primary timing signal is provided by the distributor. Without this signal there will be no sparks and no main injector function. If you have motronic then you need speed and ref sensor signals as well as a 'start' signal to the ECU before you can get spark etc.

cheers

[Hefeweizen]

Rainer,
You have probably already seen this; it's from an '83. http://shark.armchair.mb.ca/~dave/BMW/e24/e24_83.pdf
This shows a green wire from the ignition switch going to the primary side of the coil. Hope that this helps! Toph

Thanks! Yes I did see the diagram for the 83 but the 81 is different. I do have the location for the green wire and it does plug into the distributor (Dizzy Cap). The question was if that green wire has any power at all. Also, on the diagram I attached you see that there is a black and a black/red wire going to the coil but it does not show which color goes to positive and negative.

[Brucey]

as per the diagram above the +ve blk/red wire is drawn as connecting to the + side of the coil. (The coil will still work if wired in reverse, just slightly less well BTW).

The green wire to the distributor is (for L-jet) the primary timing signal for the whole engine, and connects to a hall-effect sensor within the distributor.

You do have L-jet, right?

cheers

[tschultz]

Excited to see you getting this car going finally!

[Hefeweizen]

as per the diagram above the +ve blk/red wire is drawn as connecting to the + side of the coil. (The coil will still work if wired in reverse, just slightly less well BTW).

The green wire to the distributor is (for L-jet) the primary timing signal for the whole engine, and connects to a hall-effect sensor within the distributor.

You do have L-jet, right?

cheers

Thanks Brucey! If the L-Jet is the one without the points, then yes.

So you are saying that the green cable transmits the pulse and has no current? Thinking that the coil may be fried since I do get power to the coil but nothing seems to get out of it.

[GRNSHRK]

OK, right out of an actual wire bound hard copy electrical troubleshooting manual please refer to the attached PDF

And as per Brucey (like he's ever wrong ) the red/blk wire goes to the + side of the coil and the blk wire goes to the - side

On my '80, that green wire from the dizzy disappears into a wiring harness, but the diagram shows that it sends a signal from the impulse sender to the ignition control unit, "solid state", gotta love it

Hope this helps Rainer

[Hefeweizen]

OK, right out of an actual wire bound hard copy electrical troubleshooting manual please refer to the attached PDF

And as per Brucey (like he's ever wrong ) the red/blk wire goes to the + side of the coil and the blk wire goes to the - side

On my '80, that green wire from the dizzy disappears into a wiring harness, but the diagram shows that it sends a signal from the impulse sender to the ignition control unit, "solid state", gotta love it

Hope this helps Rainer

Thanks! I really appreciate all the help!

[Brucey]

that is an interesting diagram because it shows the operation of the ballast resistor in more detail. It looks like there is always some ballast resistance with this setup (0.6 ohms when cranking, 1.0ohm when running). If someone has changed this arrangement then it could be bad for the rest of the system.

In order for you to get 'spark on cranking' with this system , the ignition control module needs to be in good order, it needs to see volts from several sources (from the combi relay and the key I think) , the coil needs to be good and have a good power feed, and the distributor pulse generator needs to be operative.

The best method for troubleshooting this lot would vary with the facilities etc available. A good method would be to check all connections where possible, and have 'known good' parts to substitute until you find the duff item. A lot of L-jet users carry a spare combi-relay, they don't last forever.

If you monitor pin 13 on the diagnostic plug it should look like 12V with the ignition on (if the coil primary is good and there is a feed to the coil), but then show a strong AC signal on cranking (if the pulse generator and the ignition control module are good).

BTW later LE-jet systems (as fitted to some M20s as well as 2.5 and 2.8 litre M30s) look a lot like this but there is an additional box in the system (like there's not enough already... ) that (IIRC) adds mapped ignition adjustments according to load (as inferred from the ECU fuelling signal) to the vacuum and centrifugal ignition timing as derived from the distributor. I have often wondered if it is possible to add this unit to an earlier L-jet system; it allegedly improves fuel economy.

cheers

[Hefeweizen]

Got it figured out! Both cables are red/black but one is thinner (-) and the other is thicker (+). I swapped out the coil and do have a spark now. The old rotor was busted and I got a new one. Bad part is that it is not the right size. No idea what O'Reileys looked at. Should have that rascal running soon!
http://house-calls.us/RickBMW633P2.html

[tschultz]

I hope you get it running soon!I have a feeling you will like that engine a lot!

[Hefeweizen]

Yes me again! So I have the car running now but it keeps shutting off after driving it for a while. The last time the car died, I checked if I still get fuel, which I did. Then I checked for spark and I did not get a spark at all. Playing around with the ballast resistor and all the connection and voila, I did get a spark. I had the ballast resistor hanging there and when I wanted to mount that part back on the wall I burned my fingers on that part! My guess would be that the heat to that extend is not normal? How does one test the ballast resistor?

[hornhospital]

Ignition ballast resistors normally run very hot, too hot to touch. They usually have a metal tie-down strap that doubles as a heat sink. Although the resistor may be the culprit, I would suspect the coil itself first. I've had two of them die, one in my 1987 E30, and the other in the 1984 633. Each got incredibly hot before they died.

[Hefeweizen]

That sure is good to know! Thank you so much!

[tschultz]

OK, right out of an actual wire bound hard copy electrical troubleshooting manual please refer to the attached PDF

And as per Brucey (like he's ever wrong ) the red/blk wire goes to the + side of the coil and the blk wire goes to the - side

On my '80, that green wire from the dizzy disappears into a wiring harness, but the diagram shows that it sends a signal from the impulse sender to the ignition control unit, "solid state", gotta love it

Hope this helps Rainer

Great document there Bobbo!! Helped me to clarify my ballast resistor wiring.