Originally Posted by choptankman
I am new to the forum but a BMW owner for 20 years (R60/6, RT100Rt, K100RS, R100RS,K75S and now a K1). I recently purchased the 1990 K1 as a project. It did not run and the transmission was toast. I bought a new fuel pump and got it running. Not great but not bad either. I have since replaced the trans, driveshaft and rear drive. Everything works on the bench. I hooked up the fuel tank and turned on the ignition. The fuel pump does not activate. This was unexpected since it ran before I replaced the drivetrain. I have checked the power to the fuel pump harness and I have voltage to the brown and white leads on the power supply side of the connection to the fuel pump. I have power to the fuel guage. When I connect the fuel pump direct to a separate power supply, the pump will run. When I connect a power supply to the brown and green leads on the fuel pump side of the harness, the pump runs. But it will not run under normal conditions. It could be the fuel pump relay, but I have no reason to believe that it has gone bad. Has anybody had similar experiences with fuel pumps? If so can I get some input on how I acn troubleshoot this problem? Thank You all for any thoughts you may have.
Tom Keating Church Creek, Md.
You may wonder where Church Creek, Md. is. It is 100 miles and 50 years from Washington, DC
Hi have you traced your problem.
Like you I am trying to get a K1 running. It belonged to a young man of 80 who sadly passed away in his prime. Only clocking up 5 800 Km (the bike). It looks new but inside of the tank was a hornets nest of disintegrated rubber seals. Pump was faulty as I believe the "flingers" had chocked up with gum. There was no sign of wear on opening the Al casing but it was impossible to turn. I have managed to find a similar pump off a BMW car and have fitted an input screen. Now the similarity in questions:
All the wires but for the earth in the tank have corroded off.
Of the four wires to the tank plug the brown is earth and the yellow is from the fuel gauge.
There is about 11.5V on the white wire, battery at 12.5V but it drops when connecting the pump i.e. "On Load" and strangely the fuel gauge drops to empty.
I cannot trace the white wire. The ownerís wife tells me that he took something out for repair but does not know what it was. Also as meticulous as he obviously was, the Manual is nowhere to be found. Is it worth ordering one?
From your correspondence it seems that it might be the pump relay that is missing. Perhaps confirming the supposition, the very clean relay compartment has one unconnected white 4w plug and a couple of empty spaces.
Can anyone help with advice, electrical diagram and placement of any component that might interrupt the pump supply? Did I say that the pump runs freely when connected to any 12V supply? I can send photos if it would be of any help.
Sunny South Africa