1995 k1100:is there a short in my fuel pump?

[1984bmwk100]

I am new here. I did search discussions on fuel pump issues, but I have found conflicting descriptions on the site, hence posting a new thread on a common topic.

My 1995 k1100 is not starting after hibernating for about 18 months. No fuel pump sound when I put the key 0n ignition with the kill switch on on position.

First, some folks here have said that he pump starts only when the button is pressed. However, my 84 k100, 93 k1100 (and even a 2000 k12) makes that sound without starting the engine, so I would like to know which flying bricks do not make the sound just with the ignition on.

Assuming the behavior was not normal, I checked the fuel pump connector coming from the relay box side. I am checking the green and brown wires. With just the ignition on, I do not get voltage and I get more than 10 v when I press the start button. This will make sense if some bikes did have this behavior as normal. (It does make diagnosing difficult since it is hard to hear a pump with the engine being cranked)

I thought of checking the pump by directly connecting the pump to 12 v. As soon as I touched the green wire to the positive, I got a spark. I am guessing there must be a short. I am not sure if the pump is bad or the connector or wiring is messed up. I am also confused how the bike developed this issue just by sitting.

Any recommendations on next steps?

Also, all circuit diagrams say the wire is green\white, but my bike has solid green wire. Also, manual shows only two wires coming from the pump. What are the other two wires for?

Thanks!

[Laitch]

I am also confused how the bike developed this issue just by sitting.

Being idle for long periods of time—18 months is a long time—is likely the most common reason for Brick starting or running issues and has been discussed here often. Electrical connections—including those within the ignition switch and kill switch—corrode. Batteries discharge. Fuel becomes stale from water infiltration and separation. Fuel lines start disintegrating. Vacuum fitting and rubber components crack open. Injectors fail to operate, and so on.

Please describe the storage conditions of both the Brick and its battery. Tell us your history with it.

[Scott_]

The '95 will have the motronic engine controller.
With this controller, if safety switches are closed, the fuel pump should prime(or at least the fuel pump relay will energize) when the key is turned to the ON position.
The aforementioned safety switches are: kill switch in the on position, side stand in the up position(older bikes didn't have this switch).
It is not uncommon for the side stand switch to fail as it is on the bottom of the bike and semi exposed to elements.

Re the 4 wires to the fuel tank connector. 1 for fuel pump power, 1 for ground, 1 for fuel level gauge, 1 for low fuel indicator lamp.
Brown is always ground(connected to negative post on battery/frame) for BMW.

If you get a spark indicating current flow when connecting the  pump wires to a 12v power source, it's possible your pump is seized. I've read that some have removed a seized pump and soaked it in some techron, or other injector type cleaner to free it up. Sometimes it worked, sometimes not.
You can source a non BMW pump for replacement if needed. There are other threads that discuss this.

[1984bmwk100]

Thanks, the bike was stored in a semi covered area with a good cover and battery removed. I have another K1100 (1993)  that was stored similarly and the fuel pump whirrs OK. The battery I am using for testing is a newer Odyssey PC680 that is good (full capacity and full charge, checked with a battery load tester).

So I did the 12 V direct connection to the fuel pump again this morningg. Looks like you are right about the freezing of the pump. I hear a click and nothing happens. So I will have to take it out. I do have an older K100 tank which most likely has a good pump. Did K100 and K1100 use the same fuel pumps? Otherwise I will go ahead and order one.

I also looked under the kick stand I do not see any connectors, switch or wire. Did 1995 K1100 have the kick stand safety switch?

[1984bmwk100]

I did some more diagnosis and after reading the forum it looks like the problem is two-fold. I am now able to get the fuel pump running when connected to 12V (I took it out and cleaned the contacts). However, no whirring sound when I switch the ignition and kill switch to on position. (like it should as  you have confirmed that).  I think the problem might be kick stand related, but I do not see any wires from the kickstand.

[volador]

If moto is stock there's a side stand switch down there some where



Bypassing the switch http://www.motobrick.com/index.php/topic,574.msg1507.html#msg1507

You can use contact ring part number 61121459998 or whatever means necessary to bypass the switch.
The OE bypass connector


The side stand switch connector

[The Mighty Gryphon]

Are you absolutely sure the problem isn't the four pin tank connector???

[1984bmwk100]

That is a good point. I was checking by poking the wire since it is difficult to check inside the connector without shorting. I guess I will just change both sides of the connector.

[1984bmwk100]

Update: The problem was indeed the 4 pin connector, probably corroded from inside. I bought one from amazon and it solved the starting issue. Thanks !

[Laitch]

Update: The problem was indeed the 4 pin connector, probably corroded from inside.

Thanks for the update. It's encouraging when reading to the end of a thread to find a resolution for the problem.