K1 fuel pump malfunction - K-Bikes.com - Excellence in Motion
 
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post #1 of 10 (permalink) Old Sep 4th, 2007, 4:49 pm Thread Starter
 
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K1 fuel pump malfunction

Hello;
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
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post #2 of 10 (permalink) Old Sep 5th, 2007, 10:53 am
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You've gone so far as to check no voltage across the pump so the next step backwards is to the pump relay and its control.

On a KRS the pump is part of the 'Kill Switch' which takes power off the relay coil. Don't know if you have one of those.



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post #3 of 10 (permalink) Old Aug 2nd, 2008, 9:06 am
 
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Jeff (Fuel Pump)

Quote:
Originally Posted by choptankman
Hello;
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.

Jeff Murley
Sunny South Africa
[email protected]

Last edited by Jmurley; Aug 2nd, 2008 at 9:23 am.
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post #4 of 10 (permalink) Old Aug 3rd, 2008, 8:19 am
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If the pump works on a battery and doesn't installed in the bike then I'd check fuses and the pump relay after obvious things like kill switch etc. You probably ought to get yourself a BMW or Clymer shop manual. These bikes are very complicated for quick fix solutions over the internet.

Here's a diagram of my K1200RS, yours may be similar. You should be able to trace the wire from the pump connector back to a relay using an ohmeter.



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post #5 of 10 (permalink) Old Jun 18th, 2009, 11:11 am
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So what did you find out...
I am having very similar problem on 2003 K1200GT...
I thought it was the fuel pump..
But, once in knee deep, pump in hand, power straight from battery pump works.
The plug doesn't seem to get 12 volts...

Could it be a simple battery dieing?

It turns bike over.. actually I started the bike took off for a hundred feet/yards and it died...
I think it might have tried to cycle thru braking system and determine not enough juice, turn off bike...

Please anyone, help...

Thanks,

Gbr
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post #6 of 10 (permalink) Old Jun 18th, 2009, 6:33 pm
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You haven't a cat in hells chance of sorting these kind of problems on such an electronically complex motorcyle without a wiring diagram and the knowledge and skills to fault find using it.

There could be many things wrong. The fuel fump relay is linked into the ECU. The pump is primed to pressure via the ECU when you first turn on the key and gets power once the motor is running. That's to make sure the pump stops pressure when the motor stops (safety feature). There's also interlinking to the engine cutoff too,



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post #7 of 10 (permalink) Old Aug 31st, 2014, 1:36 pm
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K1 fuel pump

I also am restoring a 1992 K1 that sat in storage for three years. I also have the same problem. The fuel system was all full of bad gas, the pump vibration sleeve had completely disintegrated , the fuel gauge did not indicate an level. The tank was full of bad smelling old fuel. I completely stripped the tank and components, a trip to Bobs BMW and $500i in parts and I was reassembling the fuel system. I tested the old pump and it works fine. I also noted the same issue, before disassembly it he pump did not run when you turned on the key. I trouble shot the issue and it looked to be the fuel pump relay or the logic that controls the relay. (ECU) master relay or ECU itself.

The Clymer manual is only a partial helper. It has the schematic for the K1, but the description for the 16 valve engine fuel ECU operation is sadly lacking. Above the fuel relay, it's of little help at all, it even tells you to go to the dealer is you suspect any type of ECU control problem. It does state that an ignition fault will prevent the fuel pump from running. But that's it, so much for Clymer. There are 4 relays inside the black box under the tank with 249 stamped on them, they are identical. One of the relays is for the fuel pump. You can swap them around if one is faulty you will see the fault move to a different function. However it is probably not faulty. Here is how the circuit works. The fuse with the R/G wire provides the +12 vac to the fuel pump relay coil, the circuit then goes through the side stand switch, then to the Motronic Relay. Here the circuit is made when the Motronic relay contact is closed which provides the ground path for the fuel pump relay to run the pump. So check the side stand switch first or jumper Across the switch to see if it is the problem. My problem is either the motronics relay or the ECU has locked out the fuel pump by controlling the motronics relay. Most likely we have a fault in the ECU that locks out the motronics relay. Other things are operated by the Motronics relay. The Motronics switch is interlocked with the combined switch (kill switch) and the clutch switch. The relay is also connected to the ECU (Motronics Control Unit). I believe the Motronics relay is energized or deenergised by the ECU, that circuit is completed through the clutch switch and kill switch to ground, completing the circuit for the Motronics relay, allowing the pump relay to energize, to run the fuel pump. I have not completed my trouble shooting on all the circuits yet but I think this is how it works.

Call me so we can compare notes.
3023450519

Middletown Mike
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post #8 of 10 (permalink) Old Sep 1st, 2014, 4:04 am
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You seem to have worked it out. I answered a similar question on the KRS Forum.

If you want to eliminate the ECU and interlocks from the equation it should be possible to unplug the ECU, find the output control pin in the harness connector and connect that to +12 volt (or it may go low so try 0 volt). If the relay and pump operates then you know the pump relay and pump wiring is o.k and you should be looking for a fault in the interlock switches - stand, clutch and gear shifter switch.



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post #9 of 10 (permalink) Old Jun 22nd, 2015, 11:39 am
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Fuel Pump

Yea, I had the same exact issue last winter when I restored a K1 that had been sitting for 3 years (with old gas in tank). Here is the problem: Its the connector on the tank side of the harness. The wiring inside the connector termination pulls out. I had replaced the fuel sender unit which provides the harness for the combined sender unit and the pump. I solved this problem by separating the two circuits onto separate connectors (Automotive water proof connectors). You can find them on EBay for a couple of bucks. Be aware that the sender units corrode quickly inside the tank from the new Ethanol based fuels These parts are made of Steel and cannot handle the moisture in these fuels. This could also be your problem since it is the wiring connector in the tank for the pump. I replaced mine first before I found the connector problem.

Middletown Mike & Blue Beemer
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post #10 of 10 (permalink) Old Jun 22nd, 2015, 11:46 am
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Fuel Pump

If you have a doubt about the fuel pump relay, you can swap it for the other relay in the box. There is a duplicate relay for some other service that's the same in the box. Most likely its not the relay or the ECU. Stay away from the ECU if you don't know what you are doing. Do not connect a meter to it or you are going to add to your shop bill!

Have the fuel injectors serviced before you run the system, replace all mounting O-rings. Replace fuel filter in the tank.

As far as the fuel pump goes, there are two issues you need to understand. One is the rubber sleeve on the mounting bracket. This rubber rots when exposed to ethanol fuel. Yes it disintegrates into the tank and plugs up the works. Yes the fuel pump screen is no longer MFG or supplied by BMW and yes you do need a good screen on that pump, or else. Fortunately you can get a like type of screen from Bobs BMW in Maryland. He has found a replacement unit that works with the pump.

You should replace all other rubber stuff inside the tank and outside the tank. You should test the fuel pressure regulator once you get the pump running. Install a pressure gauge on a "T" with the supply fuel line and verify 35 psi min is being regulated. Keep the gauge on the lines when you start the bike and make sure it gives you 35 psi, (it will bounce around a little because the injectors all fire at the same time), that's normal. Flush the system for a few seconds into a bucket (not the gas tank) to get rid of any old stuff in the lines.

Once you fix all this crap, if you really want to help in the way the bike runs, replace the fuel injectors with ones with the 4 hole pattern. You will increase your mileage and improve your low end and starting ability of the engine. 1980s injectors are not as good as modern injectors. Its a big difference.

Good Luck
Middletown Mike
& Blue Beemer

Last edited by Medobson1; Jun 22nd, 2015 at 12:01 pm.
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