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95 1100 LT just quit while going down the road

69zeff65

Active member
1995 K 1100Lt with less than 30,000 on the clock quit while I pulled up to a traffic light. I've tracked it down to fuel pump not running but the fuel pump is fine. Checked the wiring from the sending unit connector to the fuel pump and its good. Checked the kick stand switch and its harness and it is good. I've played musical relays with no luck either. do I need to start shopping around for a Motronic ECU so I can get out and enjoy ridding or am I missing something obvious. Its pretty much an unmolested and clean bike but it has sat most of its life.
 
I suspect the Hall Effect Sensor (HES) has failed.

Do you have spark?

Does the fuel pump come on once when the key is turned on?
 
It has spark

Paul

The fuel pump does not run at all. Before I pulled the tank off and released the fuel pressure it would fire but quit like it was out of gas. I've checked and I get no voltage at the fuel pump and I just checked the feed to the fuel pump off the bottom of the fuel pump relay and I get no voltage when the key is turned on. The power lead to that relay has 13+ volts.
 
First place I looked

#6 I believe, musical fuses and relays was part of my roadside fun. I get 13 + volts to the supply side of the fuel pump relay and that's where it ends.
 
Wait ... no voltage on the power side (or whatever you call it; not the coil side) of the fuel pump relay? Shouldn't that go straight to battery? (Through a fuse, I suppose.) That would be a bad relay, or wiring fault, no?

If you're certain there's no power happening there, then that's it. Otherwise, I'd say have a look at the connector between the tank sending unit and bike wiring harness.
 
This may or may not apply;

On 2valve Ks, the fuel pump does not come on with the key. You must push the starter button to get power to the pump. This will only last for a couple of seconds unless it senses that the engine has started (signal from the Hall Effect sensor).

I do not remember if 4valve (late K100RSs and K1100s) operate the same way.



:dance:dance:dance
 
Its not the same as a 2 valve

The four valve (my LT) is different than the two valve. When you turn the key on with the side stand up, in neutral and the idiot switch(right side kill switch)set to run the fuel pump should cycle for 1-2 seconds. It starts back up after the motor is cranked over to start the bike.

James in Ca. I have a pretty good working knowledge of relays and how they operate, unfortunately I don't know the proper terminology and I have a rather significant color vision defect so its a challenge for me to give a precise description other than to say the power supply to the fuel pump and Motronic relay is 13+volts, the switching circuit for the relay is not getting any switching voltage so the relay is not operating as it should.

The wiring harness from the relay to the fuel pump has been checked with an ohm meter and it is good, I have it out of the bike and in my hands and have manipulated the harness both before and after the sending unit so I don't think its the wiring.

I am going to dig in a little and check some ground straps and a couple other things.

Can anyone out there tell me if the FI ECU has anything to do with the initial 1-2 second fuel pump run up when the key is switched on. I would like to eliminate or isolate this as the problem so I can either look for one or not worry about it
 
Similar to the K 75S only different

Update on my ongoing adventure with the K 1100LT. I purchased and installed a new Hell Effect Sensor, properly I might add and nothing has changed. Good spark but no fuel pump or power from the F/P relay to the pump. I'm getting a little deep into this very clean low mileage K bike but at some point it might be parts for sale. Any more ideas???
 
Similar problem in the past

Sounds like the same problem I had in the past. Can't remember if it was a K1100 or a K100 but I removed the right battery cover and toward the bottom of the tank the fuel pump plugs into the wiring harness. Although it was still plugged together it lost connection. Simple plug replacement and problem solved. Good Luck!
 
I checked continuity

I have been busy with the ohm meter checking this and checking that. I will double Oh wait quadruple check the wiring between the F/P relay and the in tank F/P connection just to make sure I have had enough frustration with this fine but silent machine.

I hope I have missed something very obvious and can send all my helpers a six of their favorite beverage out of sheer embarrassment!!!
 
"Veerdy Interesting"

First thing I will do is clear the bench, then I will recheck the wiring harness and fuel tank sender. I will try getting in and cleaning(my God its tight)the Motronic connections and last but not least put the finishing touches on my "parting out a 1995 K 1100LT" 100% complete with some nice new parts and was running great until a Gremlin took over and won the game.

Great info and I will make it a point to try everything mentioned in the post.
 
Also go over to advriider.com and make contact with user named duck. He has a habit of picking up complete or semi complete K bikes others have given up on and getting them ridable. He might just have a few clever ideas. Overall I am willing to bet a quarter that this is actually something simple. The challenge is finding it without muddying the waters with other issues.

NCS
 
The Gremlin took a short break today

I know there is a smiling Gremlin somewhere nearby. I cleaned connections along with the tiny tiny Motronic terminals and started testing from scratch.

I removed and relocated the F/P, sender and related harness to my not so cleared work bench.

I got a spare 12 volt battery, volt ohm meter, some extra jumper wires and a good dose of relax and take my time.

I jumped right in and tried the old power up the fuel pump through the harness and sender trick resulted in the fuel pump coming to life with a sweet little buzz. Interesting! I wiggled wires, bent and folded them up and the fuel pump would still go strong at each attempt.

So I moved to the bike.

I checked continuity and function of the side stand switch at the right side connector, it checked out good.

I double checked to make sure all my relays were in place and the Motronic F/I plug was snug, just for laughs I bridged the side stand connector(for the 3rd time) and I checked for any voltage readings (key off) at fuel pump power supply pin socket on the frame wiring harness, found nothing. I switched the key on and got a 2 second 13 volt reading, hit the starter button, the motor cranked and the I got a constant 13 volt reading at the pin socket. PROGRESS!!! Something worked but I just don't know what because all the previous checks showed no voltage at that pin socket and no voltage reading coming from the F/P relay.

I plugged the fuel sender connector into the main harness with the fuel pump still attached and turned the key. Nothing! I ran seperate ground wire to the body of the the sending unit and tried the key again. Fuel pump ran for 2 seconds, shut off and then restarted when I cranked the bike over. Progress again!

I removed my side stand switch bridge wire and reconnected the switch to the system. I tried the key and the the fuel pump ran 2 seconds and shut off, cranked the bike and the pump ran as it should.

WOW, I fixed it but I don't know how!

I left everything as it was, shut the light off in the garage and came in for lunch. I returned to the bike after lunch just to check again to make sure it wasn't a dream. The Gremlin had returned! All I did was turn the garage lights on and walk over and turn the key on and got no fuel pump action. Bridged the side stand switch again and still no fuel pump. So I went to work.

Its getting closer to being a parts bike than it could ever imagine!
 
another thought

Have you checked the kill switch for possible dirty contacts? The switch contacts can get dirty over time just sitting in the run position and can cause the now it works and now it doesn't work. The switch is not sealed so dirt and grime can get on the contacts. Clean using contact cleaner. If you take the switch apart remember their are small parts inside that are spring loaded to the fly apart position! I believe the the side stand switch and the kill switch are in series. I faced a slimmer problem (95 K1100RS) and a dirty kill switch was part of the problem.

With the key on watch the fuel gauge as you flip the kill switch on and off, the gauge will drop to zero when the kill switch is off and come back to life with the switch in run, if the gauge doesn't come alive with the key on and the kill switch on, theirs you problem (or at least one of them). :thumb

Cheers,
Merle
 
I ran seperate ground wire to the body of the the sending unit and tried the key again. Fuel pump ran for 2 seconds, shut off and then restarted when I cranked the bike over. Progress again!

On one of the bikes that I worked on that had a similar problem, the ground was bad where it went THROUGH the plate. Ground from inside wires were good to the plate, but the wire that was firmly attached to the plate on the outside was not making conductivity to the plate. Cutting the wire and putting a ring terminal to one of the mounting screws fixed it. You problem might be on the ground side.:dunno



:dance:dance:dance
 
I think I have one of the Gremlins cornered

I put my volt/ohm meter away today and did a little smoke, spark and weird behavior testing before heading off to my job as a nuclear weapons disarming tech. Only kidding about the job. The gas tank is off the bike and the fuel sender, harness, pump and all the wiring is removed but still a unit and sitting on an old pair of jeans where the seat(and my butt)should be for the purpose of testing, trial & error. 98lee you hit on something there because I did the same extra ground thing to the fuel tank early on after I saw a little arcing under the tank when I first got the bike, I just didn't want to blow up its as simple as that.

Here is what I did today and what I found. I connected everything as it should be and I bypassed the side stand switch with a jumper wire. I set the fuel level float at about a half tank , turned on the key and no fuel gauge or pump response. I shook the sending unit(4 pin)connector and the gauge needle went nutz but still no pump. Upon closer and much more aggressive testing of the connection I found it might be best to replace the 4 pin OEM connector with something a little more suitable and durable for its application. I checked with the dealer for an OEM replacement and the response I got told me I should upgrade that connector just a little as BMW no longer supplies that connector. I will be upgrading the side stand switch connector also because amazingly enough I could get the Motronic and fuel pump relays to click away with just a twist of the wire behind that connector.

I must remember from now on continuity does not mean a good connection, just a connection at that time.

Still got the K-bike parts for sale add saved I just hope I don't need it.
 
That DOES sound like a ground problem as the four wires going to the tank are: Fuel Pump +, Fuel Gauge ground lead, Low fuel Light ground lead, and Chassis Ground. The gauge and light lead go through the sending unit (float) and then find ground through the common Chassis Ground. The most likely to affect both pump and gauge at the same time would be that common Chassis ground.

I'm not sure (as I don't have a K11 schematic in front of me) if that common Chassis Ground lead goes through you sidestand switch (that would be a logical way to route it). I'll check the schematic in the morning.


:dance:dance:dance
 
The common chassis ground wire goes straight from the fuel sender plate through the brown wire in the 4 pin connector to frame ground. It does not go through the side stand switch. It is used by both the fuel pump and the fuel level sender.

The most common failure point is where the tab on the end of the brown wire is soldered to the outside of the sender plate or where the tab on the end of the black fuel pump ground wire is soldered to the inside of the plate.

For testing purposes, run a good ground wire from the ground side of the fuel pump (black wire side) directly to the negative side of the battery or a very good chassis ground (possibly the left side of the tranny near the shifter where the battery ground lead connects) and remove the black wire from the pump. The pump should consistently work, but the fuel gauge should still be flakey.

If so, then run another good ground from a bolt going through one of the sender plate holes to the same battery ground. That should make the fuel gauge work consistently. If so, remove separate ground from pump and reinstall black wire. If both pump and gauge still work, the problem is the brown wire on the outside of the sender plate between the plate and the frame ground. Most likely it is the solder joint between the end tab and the plate. If so, cut the wire at the tab and put a ring terminal on the end and loop it over one of the plates mounting studs. Thoroughly clean the area where it makes contact to the plate. That is a more reliable fix than trying to resolder the connection .



:dance:dance:dance
 
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