Hi,
K1100LT-96 model

Bike stopped along the road and there are some mystery to be solved.
Obvious sign is:
fuel pump keeps on going when igniton is turned on.
Temp light on disply does not light up.
All relays checked out to be good.
Fuel pressure aporox 35 psi and keeps up pressure after ignition is turned of.

By closer study it seems like the ECU is restarting or is glitching quite rapidly.
So the Q is whether this is harness related or the ECU unit itself has gone bonkers.


Any experience or checks to made out there.
Ideally I would mont the ECU to a test device, but i do not know if such a test bench is avaialable.

JanP

Possible contact issue, pull the ecu connector and clean it. Check for corrosion on the pins. Reseat it and see if that is it.

My bricks a k100, so not familiar with 1100's, but I'd guess the temperature light doesn't come on unless the engine is overheated. Are you sure the fuel relay is good? Let's spose the earth wire from the fuel relay to the motronic has worn insulation and grounding to the frame. I think that would match your fuel pump symptom.

Fuel relay, swap with horn relay and see what happens.

But also check what Daveyon said, there are routing issues with some of those wires.

Hi guys,
Thanks for the input.
1. Relays has been checked and horn & fuel relay has swapped position. In an earlier post regarding fuel pump Rick or Inge stated that the Motronic controls the relay by earthing the coil circuit.
I used a pair of lock wires into the 85 and 86 position(coil circuit). I hooked up the wiring on the 85 & 86 pins on the relay. Seems like you need some electrical load to do this test. Anyway, with key in off position , there is zero reading on the multimeter. With the ignition in on position I read battery voltage. 12,4 VDC if I remember correctly. This should only last for 1,5-2,0 seconds before the motronic shut down the fuel pump by removing earth reference on coil circuit. It stays permanently on as long as the ignition is on.
Normally, the fuel pump should not start before hall sensor for cyl 2&3 start pulsing.
How this relates to the temp lights on or off I do not know(yet), But This light is probably controlled by the Motronic. Temp gauge is most likely pure analog.

I will look at the wiring diagram to clarify some things while I will look for another brick in the neighborhood. If I find one, I will test with another ECU just to see what happens. I found a used one in France on ebay yesterday for 134€. Hopefully I will come to Norway in a week or two.

JanP

JanP wrote:Temp light on disply does not light up.

The temp light bulb only lights when the engine is overheating. The fans operates to keep the engine temperature under control; the bulb won't light when the fan is running unless there is not enough coolant in the radiator or the water pump isn't working correctly. Of course, the bulb itself should not be defective.

daveyson wrote:My bricks a k100, so not familiar with 1100's, but I'd guess the temperature light doesn't come on unless the engine is overheated. Are you sure the fuel relay is good? Let's spose the earth wire from the fuel relay to the motronic has worn insulation and grounding to the frame. I think that would match your fuel pump symptom.

I will investigate, but when testing #85 coil circuit on the relay it did not have connection to ground unless the ignition was turned on. 
#85 is connected to pin#1 on the Motronic accordingly to the diagrahm I have.

Laitch wrote:

JanP wrote:Temp light on disply does not light up.

The temp light bulb only lights when the engine is overheating. The fans operates to keep the engine temperature under control; the bulb won't light when the fan is running unless there is not enough coolant in the radiator or the water pump isn't working correctly. Of course, the bulb itself should not be defective.

Thanks.
The mystery here is my assumption(I know assumptions make an ASS of you U and ME) that this light should light up when ignition is turned on and then go to sleep as the engine starts. If critical temp is reached then it will illuminate.
On the diagrahm B9560 is the Coolant temp sensor(instrument) wired to pin 7 & 14 on the Motronic. I can not see that this is the control of the lamp. This should be clarified.
JanP

K75cster wrote:Possible contact issue, pull the ecu connector and clean it. Check for corrosion on the pins. Reseat it and see if that is it.

We have used CRC contact cleaner and toothbrush.
Of course this is a culprit if some of the the leads is corroded or teh springs on the female end is sloppy.
S mentioned I have bought another ECU from France in order to do a swap and see what happens.

Your first thread says the fuel pump keeps going when the ignition is turned on.

But it starts up when you turn on the ignition to pressurise the fuel system. Thats for a few seconds and no more. Then it should stop so you dont hear it as the system is now pressurised.

If you are still hearing it running loudly I would be looking at the hoses and filter inside the fuel tank and at the pump itself.

JanP wrote:The mystery here is my assumption(I know assumptions make an ASS of you U and ME) that this light should light up when ignition is turned on and then go to sleep as the engine starts

You are half-right about the effect of assumptions, in this case. 

The engine isn't overheated during a cold start so why should the temperature bulb light? The temperature light doesn't have a self-check circuit. I suppose such a circuit would be reassuring for some riders, but where would the adventure be then?  ABS and four-pot front brakes have already removed a lot of it. Regardless, because opportunity is being taken to post pithy old sayings today like the one concerning assumptions, I'll submit one—You can lead a horse to water but you can't make it drink. 

92KK 84WW Olaf wrote:Your first thread says the fuel pump keeps going when the ignition is turned on.

But it starts up when you turn on the ignition to pressurise the fuel system. Thats for a few seconds and no more. Then it should stop so you dont hear it as the system is now pressurised.

If you are still hearing it running loudly I would be looking at the hoses and filter inside the fuel tank and at the pump itself.

Olaf,
The tank was newbuilt in february 2022 du to most likely storing over time with e85. All hoses, fuel pump , filter, sender brand new.
When using a pressure instrument on a T-Connection and setting the ignition on for a couple of seconds and turn off again, Fuel pressure remains on approx 35 psi.
If keeping the ignition on, the fuel pump keeps running. As mentioned above I have checked the signal from the motronic to the coil circuit on the fuel relay and this is making earth reference(#85) as long the ignition is on.
If I have understood thsi correclly from previous post on the forum , the K1100 Motronic 2.2 , post 1993, should control the signal reference on this pin. Pin 1 on Motronic 2.2 to Pin #85 on fuel relay.
So either I find a K1100 in the area to do a test or I will wait for the spare ECU arriveing up from France. Ebay tells me it is been posted today:-)

Finally received and installed the used Motronic 2.2 ordered from France.
As soon the the ignition was turned on and the fuel pump stopped after approx 2 sec, I got a feeling of success.
Warning light for temp steady on and crank the starter. Engine started without hesitation and did repeat it a couple of times before I took it out and let it run until temp got so high it started the fan.

Testrun will be done tomorrow, but temporary conclusion is that the Motronic can fail.

Takeaways so far are:
1. If fuel pump runs continously with only ignition on-> Motronic might be fishy.
2. If temp light does not light up when ignition is turned on-> may be Motronic or TPS adjustment.

JanP

Here are 94+ K1100LT wiring diagrams with English labels:

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/kwiring/K1100LT.94on/1994.K1100LT.Wiring.SLP.V2.0.pdf

Thanks for the diagram.
This ease the reading with the extra labeling.

The bike have done test ride for 130 km with a combo of city driving to medium Scandinavian touring 100-110 km/h.
Engine sounds nice and all lamps and instruments is OK.

Jan
we are happy to read that you were successful
enjoy your K