What is the 4 pin connector called and how would I replace or repin it?

[cgarza1985-K100]

VIN: 0030915
Hi, I'm new to this forum and to BMW K100s. I've searched everywhere to figure out the name of this stupid 4 pin fuel connector and the shit bag mechanic who had this bike before I purchased it. I can't get the bike to start and I know it was an electrical problem that started before I bought it to learn repair/restoration and turning it into café racer.

I have been able to only find out that it's a connector that is apart of the wiring harness/loom with it's parts number from a parts fische 61 11 1 459 037. I really don't want to have to buy a used wiring harness. I'd really like to just fix/save this one. Which currently some of the harness looks good, but it has some shitty work done to it that I am also trying to sort out. Grounding issues/spliced wires done in a very bad manor.

been trying to find the short in this harness to try and turn over the bike. So fixing one problem at a time. But so far my fuel pump isn't getting power. I may have also arc welded the starter in my attempts to find the problem.  Any help or tutorials that I'm not able to find would be greatly appreciated. As I'm a visual person, but can manage a lot if I'm given a bit of direction. The Clymer manual and the forums haven't been of any help via google. The one site that is linked that would have had it a few years ago is the tills.de site. But I don't see the connector on their site.

[cgarza1985-K100]

Here are some images of the situation I have found myself in. I'm trying to fix this in a cost effective manor due to some personal circumstances, but I'm willing to acquire some tools and skills in the process.

[Scott_]

1st thing I would suggest/ask is that you put the last seven digits of your VIN into your signature line or your post so we can look up the correct wiring harness identification for you, help us help you.

2ndly, the K-bike in general don't have constant power to the fuel pump. The pump is only powered when the engine is rotating. This is accomplished by a train of items.  At the front of the engine there are "hall effect" sensors that pickup on the rotation of the crank shaft, they then send this signal to the 2 different computers, 1 for fuel injection, the other for spark. The injection computer activates a relay which supplies power to the injectors and the fuel pump. The injection computer also controls the 'ground' lead of the injectors so they turn on/off at the correct time.
This sequence will keep the engine running once started. The fuel injection pump relay is also activated when the starter button is pushed to act as a primer.

At the fuel tank connector you should have a green/white stripe and a brown wire. Browns are normally ground with BMW bikes. The green/white strip will be your pump power supplied from the fuel pump relay.
It is not uncommon for the tank pass-thru connectors to fail and not pass power to the pump.

That's kind of the basics. There are more individuals on here that are way more knowledgeable on this older Jetronic systems than I and hopefully they will chime in.


1985 K-100's are slightly a slightly different breed, in that they have a number of parts that are unique to only them.

[Laitch]

The 4-pin connector is widely called "the four-pin (4-pin) connector here. Key 4-pin connector site:motobrick.com into a Google search window and you’ll get back plenty of reading material.

You haven’t welded the starter. You’ve welded the starter relay contacts. It’s likely they can be separated just by knocking the relay with a screwdriver handle a couple of times; otherwise, you’ll need to open the relay, separate them and polish them. They will weld together again if you have a weak or discharged battery. You must keep the battery fully-charged when you’re doing this kind of work.

If you intend to restore this Brick into a monument to your creativity and hard-won knowledge, you should probably learn how the feckin' thing works. There are resources all over this site to help you. In the Service Bulletin-Brochures section, member volador took time out of his busy schedule of globetrotting and killing fish so he could upload the LE Jetronic Training Manual. Before you continue, I suggest you download it at its link in the list and look into it. It is essential to acquiring understanding of this pioneering motorcycle engine management system. There is also a BMW K75 K100 2V workshop manual in the Service Manuals section.

Your Brick was manufactured in September of 1984 according to realoem's VIN checker. Get familiar with a Brick parts fiche like the one at Max BMW or realoem. it will help verify parts by part number that will work in your Brick.

[The Mighty Gryphon]

I don't know of anyone who replaced that fuel tank connector with the same part.  There have been several approaches including 4 pin waterproof automotive connectors and my personal favorite the SAE trailer light connector.

https://www.ebay.com/itm/264911874990?

https://www.ebay.com/itm/376097810405?

[cgarza1985-K100]

Ha yeah, I've seen that trailer connector. I guess I just don't understand how the male connector works. I've drained my tank and will take it apart, but going to read up on what Laitch provided since I need the distraction today while I wait for some bad news.

Hmmm dang. those Service manuals aren't linking for me. They never open a page. They just open a new tab and fail. I'll try on my personal laptop, but seeing as I'm a web developer by trade I doubt that is actually the problem.

EDIT: yep those are deadlinks for those service manuals by johnny, but I was at least able to find the jetronic pdf

[daveson]

Look inside the relay box. Usually you will find an unused white plug there. This is the plug you want, but push the male plug into it first, to be sure, to be sure. There is a tongue and groove type of arrangement you need to line up first, before you can push it in.

[Laitch]

All document linkage problems are solved.    Let's get back to the action.

[daveson]

I've searched everywhere to figure out the name of this stupid 4 pin fuel connector and the shit bag mechanic who had this bike before I purchased it.

I don't know the name of the mechanic, but I've heard of him being called a shit bag. I'll guess he's not a mechanic, just your average, plane Jane, garden variety, shit bag.

If you go into a shop like radio shack, with the male plug and ask for something like a four pin CB radio microphone female plug, I think you will get a plug that fits. Let's say $5, then just leave the original one in. This white plug in the relay box, I think was typically used in the police versions for their extra equipment, like flashing lights and CB type radio.

[cgarza1985-K100]

Thank you all for the help. Made my way through a lot of the material Laitch recommended. I have a better understanding of the electrical system pertaining to the starting of the bike. Right now I'm trying to research the chassis wiring harness as I see that this mesh of wires is completely wrong from the OEM standpoint. Are there any materials that y'all know of for rewiring that part to the ECU. Something that gives the tools required and how to get started. I'd like to avoid soldering, but can manage it and learn if necessary. Trying really hard to figure out a way to save this harness and make some headway to getting the bike to start while I'm on bereavement leave. Been wondering if I should just buy a bunch of different gauges for the wiring from euro moto electrics, but I don't want to over buy.

https://www.euromotoelectrics.com/product-p/coloredwirespool.htm

[Scott_]

So seeing your picture of all the green/red wires that is a factory joint... there should be (1) 2.5mm, (2) .5mm, and (4) .75mm wires connected together.
The 2.5 is the power feed from the FI relay.
1 of the .5 goes to terminal 9 of the jetronic ecu.
1 of the .5 goes to terminal 15(common) of the throttle position switch.
The remaining .75 wires go to the fuel injectors for the +12 power source.

I'd say the insulation needs re-applied but the wires are supposed to be all connected together.

[cgarza1985-K100]

So they are supposed to look like that from factory? I can't fond a sinfle pic or diagram thaf has it looking like this. I'm also having a grounding issue.where can i get replacement wire that isbup to spec?

[daveson]

[quote Right now I'm trying to research the chassis wiring harness as I see that this mesh of wires is completely wrong from the OEM standpoint.
[/quote]

If you're referring to the fact that the fuel injection control unit has more pins than the plug has enabled, that's normal. It also shows that you have an altitude plug.

You want to tidy it up a bit, for example insulate the exposed wires.

What is the grounding issue?

[cgarza1985-K100]

Thank you. I woke up to chdck these so i am a little groggy but going to do more research this am as well. 

EDIT: I still can't find out why/how they are wired together in such a way to be glued together like that. It doesn't make any sense to me.

[Scott_]

I would hope that they are soldered, but if you are worried about it cut them loose and make your own connection to tie them all together, and then insulate the connection so it doesn't short to the frame.

[daveson]

EDIT: I still can't find out why/how they are wired together in such a way to be glued together like that. It doesn't make any sense to me.

Maybe they were clamped with heat, maybe some other way. I save myself a lot of time now, by sometimes asking myself, do I really need to know the answer to this?

[cgarza1985-K100]

Haha that is good. I don't know enough just yet to ask myself that question. Every opportunity is a learning opportunity until I get stuck and frustrated. Then I try to just step away. I decided to put the bike back to how it was priginally set and wrapped those wire ends in electrical tape. Since its likely they aren't my problem. I reseated all of the grounds and now I newd to test some components indivisually...as soon as I figure out how to do that and debug further.

[daveson]

Your idea of going one step at a time is good. You want to find out which lights come on when you turn the key to on.

Probably one option is to leave the tank disconnected and see if you have spark while cranking. If you have spark, the next thing to check would be fuel.

[cgarza1985-K100]

Gonna have to reset since something chsnged the last time I started, but yeah tank is staying off now. I had spark before and injectors were good, but now i need to start all over and recheck everything. Just need to find the energy to do it. Feeling pretty defeated today.

[daveson]

Think of it as a learning curve rather than a battle, then a setback isn't a loss. Then as long as you're trying, you're winning.

[cgarza1985-K100]

Oh, I'm a programmer for my day job. I am used to feeling stupid. This one is more physical on progress though.

[Laitch]

This diagram could be helpful.

Also the document from which it came also contains a detailed BMW schematic of the system. The document is titled Testing for K Models and it's in the same section where you found the LE Jetronic Manual.

[daveson]

Am I right in thinking that it doesn't crank anymore?

Which lights come on when you turn the key on?

[cgarza1985-K100]

I believe its not cranking. Ive had it disconnected this week. The dash lights come on so I think i still have to clean the brushes that Laitch told me about. Since i think what happened is my battery drained a bit at the time I was showing a drift buddy of mine the problem.

[Laitch]

I believe its not cranking. Ive had it disconnected this week. The dash lights come on so I think i still have to clean the brushes that Laitch told me about.

It wasn't "brushes" I mentioned in Post #3; it was starter contacts. Having seen the condition of the wiring, it might be a good strategy before further testing to start by cleaning all the main ground wire terminals and their attachment point on the frame backbone, the battery ground terminal on the transmission, the battery terminals themselves and all electrical connectors while you have the fuel tank removed. Faulty ground connections can be at the root of many operation failures. Deoxit D5 is an excellent cleaner and protector. Clean the plugs and pins of both the fuel injection control unit and the ignition control unit also, if that hasn't been done already.

In its un-tampered state, the fuel injection control unit plug you're displaying in Post #9 usually is thickly wrapped right up to the plug. The plug takes a hellacious left-hand bend at the frame and then joins with the control unit. We've had a few members who've had shorts in wires at that bend so that's a place to check for continuity.