On the never ending search for the solution to the misfire on my K100 LT. I replaced  the fuel pump and all the tank internals, and fitted a new 4 pin plug to the out of tank cable.
although the misfire continues the fuel pump was operating as it should. But then.........

As the Hall sensors are an issue over time. I replaced them with some aftermarket Halls. My problem is:- the bike is running with the same missfire, but now the fuel pump runs continuosly. Even if I turn off the ignition and take out the key. Fuel pump is still running, WTF I said to myself. The only way to stop the fuel pump was to disconnect the four pin plug.

Could this be a relay problem ?? Any electrical geniuses out there to point me in the right direction. ??

Cheers 
Steve

I would be replacing the relay, you don't need a special one just a matching Bosch one.
Before that try removing the relay instead of unplugging the tank connection then replacing it to see if it is the relay.
I doubt that replacing the hall sensors would be directly connected with the pump running on but co-incidental.
As for the miss what have you done to diagnose the miss (I haven't been following the forum closely lately as I have had other BMWs in my life which are problematic and giving me a right royal dose of the shits) my dad always said "son if its got tits or wheels it will give you trouble"

stevenh wrote: Even if I turn off the ignition and take out the key. Fuel pump is still running, WTF I said to myself. The only way to stop the fuel pump was to disconnect the four pin plug.
Steve

Operating the kill switch wouldn't stop it?

RicK G wrote: my dad always said "son if its got tits or wheels it will give you trouble"

More trouble; tits on wheels

Sounds like a sticky relay, but power off on the bike means power off to the pump too.
Must be more to keep it going.
The only thing that suppose to keep power is the clock.

Bit of a bugger to diagnose from a distance, but indeed try with the kill switch and update us.

Arlina wrote:

RicK G wrote: my dad always said "son if its got tits or wheels it will give you trouble"

More trouble; tits on wheels

Sounds like a sticky relay, but power off on the bike means power off to the pump too.
Must be more to keep it going.
The only thing that suppose to keep power is the clock.

Bit of a bugger to diagnose from a distance, but indeed try with the kill switch and update us.

Had this on mine. With a weak or old battery, the starter relay contacts weld together and the starter runs all the time. The headlamp / load shedding relay is earthed through the starter and so, if you have this problem, switch on the headlights and see if they come on. If they don't, welded contacts are your problem. Open the relay and fix it.

stevenh wrote:On the never ending search for the solution to the misfire on my K100 LT. I replaced  the fuel pump and all the tank internals, and fitted a new 4 pin plug to the out of tank cable.
although the misfire continues the fuel pump was operating as it should. But then.........

As the Hall sensors are an issue over time. I replaced them with some aftermarket Halls. My problem is:- the bike is running with the same missfire, but now the fuel pump runs continuosly. Even if I turn off the ignition and take out the key. Fuel pump is still running, WTF I said to myself. The only way to stop the fuel pump was to disconnect the four pin plug.

Could this be a relay problem ?? Any electrical geniuses out there to point me in the right direction. ??

Cheers 
Steve

Had this, on ALL my BMs ( and VW cars ). It's probably the Bosch metal spark plug caps. What I've had is a crack or dirt in the caps' insulators shorting the spark to earth. On all my engines I've put on non-metal caps. No more problems. On my K, I have Bougicord leads with straight caps and 90° coil connections. I've swapped the 2 dual output coils so that the 2 + 3 coil is in front because then standard Bougicord leads fit, but I can't remember the lengths. The bikes' been like this > 10 years. There's another advantage : the leads then come right up close to the BMW cover plate between the cams and you don't have to reach deep down pull the caps off the plugs.

Where did you get a new 4 pin plug for the tank ? I also need this.

The more I read the OP's performance complaint, the more I believe the ignition switch is at fault so I'm going to quit reading it.

Arlina wrote:

RicK G wrote: my dad always said "son if its got tits or wheels it will give you trouble"

More trouble; tits on wheels

Double trouble.

Laitch wrote:The more I read the OP's performance complaint, the more I believe the ignition switch is at fault so I'm going to quit reading it.

+1 A good clean will often do the trick.

Laitch wrote:

stevenh wrote: Even if I turn off the ignition and take out the key. Fuel pump is still running, WTF I said to myself. The only way to stop the fuel pump was to disconnect the four pin plug.
Steve

Operating the kill switch wouldn't stop it?

Nope !

RicK G wrote:I would be replacing the relay, you don't need a special one just a matching Bosch one.
Before that try removing the relay instead of unplugging the tank connection then replacing it to see if it is the relay.
I doubt that replacing the hall sensors would be directly connected with the pump running on but co-incidental.
As for the miss what have you done to diagnose the miss (I haven't been following the forum closely lately as I have had other BMWs in my life which are problematic and giving me a right royal dose of the shits) my dad always said "son if its got tits or wheels it will give you trouble"

" Tits or Wheels " Yeah that would be something my old dad would say. Wouldn't be far wrong either.

Phil Moser wrote:

stevenh wrote:On the never ending search for the solution to the misfire on my K100 LT. I replaced  the fuel pump and all the tank internals, and fitted a new 4 pin plug to the out of tank cable.
although the misfire continues the fuel pump was operating as it should. But then.........

As the Hall sensors are an issue over time. I replaced them with some aftermarket Halls. My problem is:- the bike is running with the same missfire, but now the fuel pump runs continuosly. Even if I turn off the ignition and take out the key. Fuel pump is still running, WTF I said to myself. The only way to stop the fuel pump was to disconnect the four pin plug.

Could this be a relay problem ?? Any electrical geniuses out there to point me in the right direction. ??

Cheers 
Steve

Had this, on ALL my BMs ( and VW cars ). It's probably the Bosch metal spark plug caps. What I've had is a crack or dirt in the caps' insulators shorting the spark to earth. On all my engines I've put on non-metal caps. No more problems. On my K, I have Bougicord leads with straight caps and 90° coil connections. I've swapped the 2 dual output coils so that the 2 + 3 coil is in front because then standard Bougicord leads fit, but I can't remember the lengths. The bikes' been like this > 10 years. There's another advantage : the leads then come right up close to the BMW cover plate between the cams and you don't have to reach deep down pull the caps off the plugs.

Where did you get a new 4 pin plug for the tank ? I also need this.

Funny you should mention the caps and leads.  I have just got back from the local Auto shop with a set of leads just as you describe. No shit, ten minutes ago

Well the fuel pump turning off problem has fixed itself. All good now....... Yeah right

I did pull out the relay and clean up the contacts a couple of weeks ago. Serves me right eh.

I'm going to fit a new one. When I can find one that is. Things happen a little slower than normal here in NZ

Just had a thought. I am replacing the ign leads and caps. the coils check out ok. I have traced the fault to no 4 cyl.

Anyone know a way to test the trigger/pulse wire to the coils. Does the this wire come direct from  the CDI

And.... do cyls 1-4 and 2-3 fire together in pairs.

stevenh wrote: do cyls 1-4 and 2-3 fire together in pairs.

 Yes they do fire together, by pairs.

As concerns the injectors, they open all 4 together, i.e. several times per engine 4 strokes cycle.