Fun and Games with an old K1100LT

[beemuker]

tested the side stand switch at the plug with meter. It is working. Pulling in the clutch also had no effect.

[Past-my-Prime]

I may choose to delete this post if it's sufficiently idiotic. . . but doesn't the fuel pump only run very briefly unless a) the starter switch is pressed or b) the engine is running? I am far from an electronical genius or any kind of genius for that matter.

[beemuker]

Call the previous owner there is a side stand switch and the last time it ran last year he says it was working and it Hass to be up to start it must be in a different location then my other bikes I don’t see a wire running up or the connector where it was on my other bikes.
Check for voltage with the side stand up and ignition key on my first turn the key it shows about 11 or 12 V and then quickly goes down to zero that wire coming from the fuel sender was pretty rough and cracked in places especially down near the sender , I may have to pull the fuel sender out and try to rewire it but it’s cracked mostly down near the bottom and I’m not the greatest at soldering I don’t think I can get a splice on it

the wires from the sender to pump are cracked so before I try to rewire I tested continuity between the ground coming from the 4 pin to the ground on fuel pump and the power from 4 pin to pump. both have continuity. Also getting power to pin 30 on relay and previously had also switched relays around. To eliminate the possibility of a bad fuel pump I removed it and bench tested. I'm striking out here so I'll go back to my other challenge and try to figure out why after rebuilding the water pump on my "96 Evinrude 90 it still is not peeing water. Lack of peeing can be a real pain. 

[beemuker]

I may choose to delete this post if it's sufficiently idiotic. . . but doesn't the fuel pump only run very briefly unless a) the starter switch is pressed or b) the engine is running? I am far from an electronical genius or any kind of genius for that matter.

Yes, but it's not even running briefly, and not starting.

[rbm]

I may choose to delete this post if it's sufficiently idiotic. . . but doesn't the fuel pump only run very briefly unless a) the starter switch is pressed or b) the engine is running? I am far from an electronical genius or any kind of genius for that matter.

On 2V K-bikes with LE-Jetronic EFI, the fuel pump ran when the start switch was pushed, not before.  On 4V K-bikes with Motronic EFI, the fuel pump runs for a short time when the bike is turned on before pressing the start switch.,

[beemuker]

On 2V K-bikes with LE-Jetronic EFI, the fuel pump ran when the start switch was pushed, not before.  On 4V K-bikes with Motronic EFI, the fuel pump runs for a short time when the bike is turned on before pressing the start switch.,

any suggestion on where I go from here? Something is keeping the fuel pump from working, but damn  if I know what.

[rbm]

any suggestion on where I go from here? Something is keeping the fuel pump from working, but damn  if I know what.

Have you verified the operation of the pump independently of the rest of the bike's wiring? Disconnect the tank from the harness and apply 12V to the pins on the tank connector corresponding to the pump - Green/White and Brown. 
- Does the pump operate?  If yes, good.  If not, check wiring.

after switching on ignition, I get no voltage at female green/white on connector.

You'll want to check the sources of power for the components of interest for getting the fuel pump to operate.  Those components are Motronic unit, Motronic relay, Fuel Pump relay.  From my documentation for a 1994 K1100LT, fuses of interest are:
Fuse 6 = Battery (Unswitched) = Fuel Pump Relay(30)
Fuse 5 = Battery (Unswitched) = Motronic(15), Motronic Relay(30)
Since these are unswitched circuits, power should be present on those pins with our without the ignition key being switched on. 
- Are you reading battery voltage on the Fuel Pump Relay pin 30 (Red/Green) wire (relative to ground)?  If yes, good,  If not, check wiring for broken wires or loose connections.
- Are you reading battery voltage on the Motronic pins (Red/Yellow) at the Motronic and the Motronic relay?   If yes, good,  If not, check wiring for broken wires or loose connections.
Now that you've verified that power is being provided and that your pump is capable of running, you need to check whether it is getting switched on correctly.  Power at pin 30 of the fuel pump relay will supply the power to the tank connector.  If you don't read voltage at the fuel tank connector harness side when you switch on the ignition, start tracing  power to the fuel pump relay coil.  It starts at the ignition switch, travels through the side stand switch, through the fuel pump relay coil and finally to the Motronic switched ground lead.
- Are you reading battery voltage on Pin 15 of the ignition switch (Green) when the key is turned on?  If yes, good,  If not, check the ignition switch.
- Are you reading battery voltage at pin 85 (green/yellow) of the fuel pump relay with the side stand up?  Does voltage drop to zero when the side stand is down? Do you get the exact same behaviour at the Motronic relay pin 86 (Green/Yellow) when you raise and lower the side stand.  If yes, good.  If not, check the side stand switch and the associated wiring.
The last piece in this puzzle is the Motronic switched ground (Blue/Brown).  The Motronic controls the ground to the fuel pump and turns it on or off depending on other sensors on the bike.   
- for test purposes only to isolate the Motronic, you can temporarily ground the Blue/Brown wire on the fuel pump relay.  That way it does not depend on the signal from the Motronic.  Be prepared.  When you turn on the ignition and the side stand is up, the fuel pump should start working if all the other tests above passed. If it does, it means the Motronic is not switching the ground for some reason.  You'll have to continue troubleshooting that problem.  If the pump fails to run even with this temporary ground in place, then the fuel pump relay is bad. Get a new one..
- 

[beemuker]

thanks Robert, some of this I've already done, I'll get to the rest tomorrow.

[The Mighty Gryphon]

I don't know a lot about big outboards, but the rubber impeller water pumps on inboards lose a lot of output when the sides of the impeller wears away the metal of the cover.  Good output depends on the water not flowing back over the sides of the impeller vanes.  If the fit is loose enough the pump won't even prime.

I don't know how many hours you have on yours, but I would suspect a 25 year old engine on a Florida boat would have a lot of hours and wear in the pump chamber.

[beemuker]

I don't know a lot about big outboards, but the rubber impeller water pumps on inboards lose a lot of output when the sides of the impeller wears away the metal of the cover.  Good output depends on the water not flowing back over the sides of the impeller vanes.  If the fit is loose enough the pump won't even prime.

I don't know how many hours you have on yours, but I would suspect a 25 year old engine on a Florida boat would have a lot of hours and wear in the pump chamber.

I rebuilt the pump using new housing and impeller. I've got a shop manual and followed it . I've had trouble lining everything up , until my brother suggested using a ratchet strap to slowly raise the lower unit, enabling you to line it up. duh still no pee ???

[Laitch]

duh still no pee ???

Maybe the impeller shaft key got away from you. 

[beemuker]

back to the bike
verified the operation of the pump independently of the rest of the bike's wiring following RBM suggestion. the wiring probably should be replaced but doesn't appear to be the problem.
When checking voltage at green/white from harness side  with kickstand up, voltage momentarily goes to 11, then quickly down to 0? some feedback loop seems to be shutting the voltage down?
 verified power at pin 30 on  pump relay
pulled and checked all fuses.

[The Mighty Gryphon]

What you describe is normal operation of the fuel pump in Motronic systems.

When the key is turned on, the fuel pump is activated for 2 seconds to prime the rail and injectors.  When the engine starts and the engine speed is sensed by the Hall Effect Sensors to be above 700rpm the fuel pump is switched on by the ECU. 

I believe you have an aftermarket fuel pump now.  I think I have the same one in my '88 K100RS.  For some reason, it does not prime the injectors as quickly as the OEM Bosch pump.  On my bike, I need to cycle it a couple times to get enough fuel pressure in the rail to fire a cold engine when I press the start button.

Have you disconnected the fuel supply hose at the rail and put it into a bottle to see if indeed fuel is being pumped when the ignition is turned on?  I would suggest a 2 liter soda bottle to contain the splash.

I could be wrong, but my experience is that the sidestand switch disables the spark.  I have flooded my engine on a couple occasions trying to start the engine with the sidestand down.

[beemuker]

What you describe is normal operation of the fuel pump in Motronic systems.

When the key is turned on, the fuel pump is activated for 2 seconds to prime the rail and injectors.  When the engine starts and the engine speed is sensed by the Hall Effect Sensors to be above 700rpm the fuel pump is switched on by the ECU. 

I believe you have an aftermarket fuel pump now.  I think I have the same one in my '88 K100RS.  For some reason, it does not prime the injectors as quickly as the OEM Bosch pump.  On my bike, I need to cycle it a couple times to get enough fuel pressure in the rail to fire a cold engine when I press the start button.

Have you disconnected the fuel supply hose at the rail and put it into a bottle to see if indeed fuel is being pumped when the ignition is turned on?  I would suggest a 2 liter soda bottle to contain the splash.

I could be wrong, but my experience is that the sidestand switch disables the spark.  I have flooded my engine on a couple occasions trying to start the engine with the sidestand down.

the fuel pump is not being activated. With the tank opened, I do not hear the pump when ignition is switched on, sidestand up. When I say momentary voltage at tank connector, I mean a flash, not 2 seconds. I am familiar with the sound a brick makes when switching the ignition on, especially with a near empty tank. Currently have the tank off to better perform tests RBM suggested on relays.

[beemuker]

results of RBM's tests:
reading battery voltage on fuel pump relay pin 30
reading 12v at Motrtronic  relay pin 30
I am not reading voltage at pin 85 of fuel pump relay with side stand up [or down]
I do not get voltage at motronic relay pin 86 with side stand either up or down. Grounded blue/brn on fuel pump relay, tank is off, but no voltage at tank connector green.
I do get 12v at red/yel at motronic relay.
I don't know how to read voltage at Motronic .?

I don't know where pin 15 of ignition switch is. Is it on a relay, or in the actual switch?


thanks for all the help. 
gotta go do family stuff now, will try to get back to it tm.

[rbm]

Pin 15 on the ignition switch is just a designation on the schematic diagram that is produced by BMW.  You should look for the green wire on the connector that the ignition switch plugs into on the harness.  Stick your voltmeter probe into the connector where the Green wire is.  If you are reading 12V on that wire with the ignition on, and no voltage on the Green/Yellow wire at the Motronic relay or the fuel pump relay irrespective of the side stand position, then you have a problem with the side stand switch or its wiring.  That's where you have to concentrate your investigation.

[beemuker]

Pin 15 on the ignition switch is just a designation on the schematic diagram that is produced by BMW.  You should look for the green wire on the connector that the ignition switch plugs into on the harness.  Stick your voltmeter probe into the connector where the Green wire is.  If you are reading 12V on that wire with the ignition on, and no voltage on the Green/Yellow wire at the Motronic relay or the fuel pump relay irrespective of the side stand position, then you have a problem with the side stand switch or its wiring.  That's where you have to concentrate your investigation.

I'm getting battery voltage at green wire [ignition switch]with ignition on or off.
I get battery voltage at motronic relay. grn/yel
I don't have a green/yellow at fuel pump relay.Pin 85 is a blue/brown. and had no voltage.
i do have voltage at pump relay 30

[rbm]

Might be a difference between 93 and 94. I do t have a schematic handy for 93.  Makes me handicapped to give accurate advise.

[beemuker]

I'm getting battery voltage at green wire [ignition switch]with ignition on or off.
I get battery voltage at motronic relay. grn/yel
I don't have a green/yellow at fuel pump relay.Pin 85 is a blue/brown. and had no voltage.
i do have voltage at pump relay 30

The Clymer K-series manual came today and it has some pretty clear [but b/w] wiring diagrams. Maybe they will help.

[beemuker]

Might be a difference between 93 and 94. I do t have a schematic handy for 93.  Makes me handicapped to give accurate advise.

My title says 1993 K100Lt
ran the vin= K1100LT, 526,536, production month 8/1992
and thanks for your help

[beemuker]

My relay box has a few sketchy items, probably related to the aux lighting, front and back, which work. But maybe not and possibly the source of my non operating fuel pump. The black plug and white plug are disconnected from their mates and do not seem to go together. There is also a blue tap.

[beemuker]

Might be a difference between 93 and 94. I do t have a schematic handy for 93.  Makes me handicapped to give accurate advise.

Yes, they are different.  The same diagram as in my manual is in the electrical diagrams section of motobrick. I don't know how to paste the link though.

[Scott_]

The Black and white plugs have no mates out of the factory. They are for add-on alarm and other "special systems".

[beemuker]

The Black and white plugs have no mates out of the factory. They are for add-on alarm and other "special systems".

thanks

[beemuker]

"Now that you've verified that power is being provided and that your pump is capable of running, you need to check whether it is getting switched on correctly.  Power at pin 30 of the fuel pump relay will supply the power to the tank connector.  If you don't read voltage at the fuel tank connector harness side when you switch on the ignition, start tracing  power to the fuel pump relay coil.  It starts at the ignition switch, travels through the side stand switch, through the fuel pump relay coil and finally to the Motronic switched ground lead."

I've reread all the suggestions but I'm at a loss where to go from here. now that I have a clear wiring diagram I'll try to figure out why power to pump is not getting switched on. Ihope it's not a problem with the moto's "brain" , just my brain.