Recently purchased a k100 Rs which had been a none runner for the last few years.

Traced the problem to the fuel pump not receiving power from the relay.

added and additional wire from the rear of the relay direct to the pump and the bike runs and all is great. so I decided to renew the wire and rewrap the loom.

Only to discover that the wire in question runs to the back of the clocks and not direct to the relay as indicated in my wiring diagram.

What signal does the instrument panel send to the fuel pump to initiate start?

Its no good rewiring the fuel pump to the back of the relay when the signal sent by the clocks is the problem.

Does anyone have a wiring diagram that may help?

Could it be anything to do with the abs ?  Thanks in advance.

On a 4V K100RS the fuel pump relay is triggered by a ground signal to the blue/brown wire from the Motronic. 

(Assuming the side stand is up and that switch is working. 12V+ to the fuel pump relay on the green/red wire.)

Another possible cause of the fuel pump not getting power is a flaky connector for the fuel level sender.

the feed to the relay looks good its the output which looks like its at fault.

andyldean wrote:Is there a way to bypass this fuel level sender?

You can run wires directly to the fuel pump through the gas cap. I had a guy come by my house once who had done that.  Crude but it did work.

(The smaller terminal on the fuel pump is 12V+, the larger terminal is ground.)

If the FLS connector is the issue:

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/fls.connector/fls.connector.htm

no its not the tank connector its definetly at the instruments.
Does anyone have a pinout diagram for the fuel tank connector?

the wire that feeds the pump from the connector under the tank is yellow and white.
this runs to the back of the instrument panel to the pin which looks like its labeled gear position indicator. also yellow and white.
cant see why none of this is illustrated on the wiring diagram.
It makes it hard to work around.

FLS connector:
---------------------
Brown - ground
Green/white - fuel pump 12V+
White - to low fuel lamp in instrument cluster
Yellow - to fuel gauge

andyldean wrote:the wire that feeds the pump from the connector under the tank is yellow and white.
this runs to the back of the instrument panel to the pin which looks like its labeled gear position indicator. also yellow and white.
cant see why none of this is illustrated on the wiring diagram.
It makes it hard to work around.

The fuel pump has nothing to do with the instrument cluster.

The only wire from the FLS to the cluster is a white wire for the low fuel lamp.

There are three wires for the GPI in the cluster:
yellow/white
yellow/black
yellow/blue
Those all come from the gear position switch on the back of the transmission.

very strange because the output from the relay has no continuity o any pin on the fuel tank connector

Solved.  The previous owner when trying to get it running must have mixed the two connectors around.
The tank connector was plugged into the gpi.
You made me think with the wire colours and I have just checked.

I thought it was odd when I took the tank off my rt and the connector pins disn't fit neatly.
Thanks again.

The green/white wire from the 87 pin on the fuel pump relay goes to the FLS connector in order to power the fuel pump.