My son and I acquired a 1989 BMW K100RS.  It was sitting for 10 years in heated garage with 3/4 tank of gas.  Bike is two-tone blue and white with ABS and cleaned up to very nice condition.  55,000 miles.  (price: $400)

We have new fuel pump, sending unit, plugs, filter, hoses, etc.

Here is the problem.   (we have been trying to figure this out all day)

1.  When everything is hooked up it keeps blowing fuse $6 for fuel pump relay.
2.  We Disconnect plug for tank under tank and it does not blow fuse.  
3.  Disconnect leads on fuel pump and connect tank plug and it DOES NOT blow fuse.
4.  Pull pump out and submerged in a bucket of gas and wire directly to battery with tank connection plugged in and it starts right up and sounds great.
5.  Hook up leads to pump and turn on key and it blows the fuse.

The fuel pump is new.  The sending unit is new - but purchased from private party. (it looks new)

Am I right to assume it is the wiring within the molded plug that connects to the tank that is part of the sending unit?  We put a meter on it and have no power but have 10.5 amps coming out of the plug that connects to the tank.

What next?  It was 80 degrees today and I sure wanted to try this thing.  

Thanks in advance,

Bigdawg
Wisconsin Rapids WI

Sounds to me that the sender unit is shorting to ground.

Disconnect the fuel pump and the connector outside the tank.
Measure the resistance between the green/white and brown wire, it should be open.

Looks like the sending unit has a short.  Paid private party $100 dollars for it.  Supposed to be brand new.  

Anybody know where I can buy one and have some confidence.

Thanks,

Bigdawg
Wisconsin

If the one you have is in good shape it should be possible to find the reason to
the short and repair it.

Look in the how to section, Robmack have a excellent thread about troubleshooting
and adjusting the sender unit.

A brand new FLS from a dealer is $124. $100 is way too high a price to pay to a third party. (Even if it works.)

Part no is 62161459565

I had to order another sending unit.  Hope that is the problem but I'm really not sure.  We had power to the plug under tank all day yesterday but now we do not.  Yes, I checked the fuse.

I found the article for troubleshooting the FI system but the flowchart does not have my original problem.  As soon as we turned on the key it would blow fuse 6 for fuel pump.  This happen immediately without engaging the starter.  

At this point, i'm going to install the new fuel sensor and start from scratch.  I will attempt to follow the TS flowchart, however right now it does not make it passed the first test, power from ignition switch to pin#86 on FI relay.  

I still think I have a strange "short" in the system but I am at a loss as to how to find it.

thanks again,

BigDawg
Wisconsin

I have rebuild several old tractors, this is a new challenge.

BigDawg7110 wrote:I will attempt to follow the TS flowchart, however right now it does not make it passed the first test, power from ignition switch to pin#86 on FI relay.  

Power to terminal 86 on the FI relay comes from the kill switch, is it in correct position?
If not the instruments also would stay dark, and a lot of this and that don't function.

Kill switch is correct position.  Lights, gauges, appear normal.

We had it running with fuel pump hooked directly to the battery.  Sounded smooth.  Can't wait to ride it.

When hooked up with new fuel sender, no power past the plug under the seat.  Power was to the plug, about 10.4 volts. but I could not detect anything after removing the sending unit and using a meter on the soldered connections that would be in the tank.  

But after 8 hours of tryinig to figure this out, I have lost power at the fuse #6.  Should power be there all the time like the other fuses?  or just when starter engages?  I would think this needs to be hot all the time.


I think I need to start over, from the beginning, go slow, use this board, and systematically narrow it down.  Thanks for the help

BigDawg
Wisconsin

At fuse #6 you would only have power when you push the starter button or,
engine is running............unless we speak about a 4V model...but then it's a -90.

Thanks.  Any idea why it would blow fuse 6 as soon as I turn on the key.  Maybe a short between fuse 6 and ignition switch.  

Is it Ignition switch ==> relay ==> fuse  or Ignition switch ==>  Fuse ==> relay ?

Thanks much,

BigDawg
Wisconsin

On a 2V, battery/relay/fuse/pump.

What do you mean "On a 2V"  Is that a model?  I have a 1989 BMW K100RS-ABS,

Thanks,

BD

It's possible that you have two different problems.
1. The shorted sender unit.
2. The FI relay is shorted to ground at the negative side of the coil,
    this is the signal wire and grounded through the ignition ECU when
    the pumpshould be running.

   Remove the relay and check if you have connection to ground at terminal 85,
   you should have open circuit.

I will check tonight and get back to you.

Thanks much for the help.  Maybe I will get to ride this thing before the snow arrives.    

BD
Wisconsin

Another less likely possibility is a internal short in the relay between 86 & 87.

It is the original FI relay?  And not a universal standard relay..........

The relay is blue in color.  Has "Hella" in top left corner.  "12V" in top right.

In the middle it says "4RA" and just below is "003 510-60".

Bottom has "Made in Germany".

I checked for power on #86 on relay.  Key on, neg probe on neg to battery.  positive probe on #86.  Kill switch in run position.  No power.  Have power on #30.  Also have power to the fuse when engaging the starter.

More info
-----------

Tonight my son wired around the "bad" fuel sensor.  He drilled a small hole through the plastic housing that goes into the tank.  Ran a positive and negative wire to the fuel pump and connected to the fuse side of accessory.  

We turned on the key and the pump ran.  The bike started right up.  We attached things put the seat on and I went for a ride.  Very impressive.  Lots of low end torque.  I finally got a chance to ride it.   We warmed it up good and it ran perfect.  Very quiet, no misses.   I was thinking we would sell it but after riding it, I'm not so sure.

We decided to wait for the new fuel sensor to do it right so we took the tank back off.

This was a fun project to do with my son and the person that sold us the bad part has agreed to return the money.

Things are good.  Thanks for all you input.

When the new part is working - I will confirm the fix.

Doug
Wisconsin Rapids WI

BigDawg7110 wrote: The relay is blue in color.  Has "Hella" in top left corner.  "12V" in top right.

In the middle it says "4RA" and just below is "003 510-60".

Bottom has "Made in Germany".

That is the relay for the pressure modulators on the ABS system.

At right front in the relay housing you have four smaller relays,
the left front of this four relays is the FI relay.

It isn't normal that the relay closing its contacts as soon as you turn on the ignition.

BigDawg7110 wrote: We turned on the key and the pump ran.  The bike started right up.  We attached things put the seat on and I went for a ride.  Very impressive.  Lots of low end torque.  I finally got a chance to ride it.

Noice..... 

There is a plate over the spark plugs what does it say on there, this could be a 16 v engine there were some with 89 on them but they came out as 1990 models. This would make a difference.

After I was in doubt about if it was a 8/16V model, I did read the first post again.
The blue/white SE model was only made in -88 and -89 as a 8V model, but it is a lot of wannabies around.

I will post some pictures tonight.  I'm pretty sure it is a 89 ABS.  It is definitely blue and white.

As far as the relay, I was going by the picture in this post.  http://www.i-bmw.com/showthread.php?t=37313 

Guess I need to really watch closely.  This is the picture from the post.  It is a K75.  I will post a picture of mine.

Rode the bike again tonight.  Very nice.  My son is now out cleaning it up and putting things back in place.  We just need to install the new fuel sensor when it comes.

I will post some pics when I have time.  Looks like I have to upload to a website first and then reference the URL.

thanks again,

BD 
Wisconsin

I think a K is good for father son relationships. Mine 'woudnt be seen dead on one of those' yet the first time he sat up on it said 'I could get to like this' in a tone that set alarm bells ringing. Enjoy the K together.

BigDawg7110 wrote:Rode the bike again tonight.  Very nice.  My son is now out cleaning it up and putting things back in place.  We just need to install the new fuel sensor when it comes.

I will post some pics when I have time.  Looks like I have to upload to a website first and then reference the URL.

thanks again,

BD 
Wisconsin

Here is how
https://www.k100-forum.com/t998-posting-pictures-and-movies

BigDawg7110 wrote: Rode the bike again tonight.  Very nice.  My son is now out cleaning it up and putting things back in place.  

  

BigDawg7110 wrote: I will post some pics when I have time.

Looking forward to see pictures of the bike and/or relay Box, as I'm still a bit
in doubt about which model you really have.

If no success with the pictures, post the last seven digits of the VIN.

These are a few pictures from the weekend.  We are putting the bike back together tonight so I will post some more pictures when the bike is all back together.  There are a few dings but overall very good.  Unfortunately the previous owner tipped it over in the driveway and broke the lens on the right turn signal.  Also has a scratch there.  

The link below should work.  It should be a directory of some image files.  If it doesn't work, let me know.  (BMW must be in CAPS)

www.camplulu.com/BMW

www.camplulu.com/BMW


Thanks again for the help,

BD
Wisconsin

That is the model I did have in mind from the start and shure is a 2 valve.
But it's the closing FI relay as soon you turn on the ignition that is a bit confusing.

It's possible that the late 2V models have the start up sequence changed to be
similar to the later Motronic euqipped models........which is more logical.

All things mounted, and bike running as I understand it?..............does the
fuel pump run for ~1,5 sec every time you turn on the ignition?
If so......could you make a picture of the top of the L-jetronic unit which is
under the seat.....of the label with the Bosch number on.

Yes,  Everything is running.  Went for a ride last night after mounting the bags and rest of the fairing.

We have the fuel pump wired to the accessory until we receive the new part.

I will remove the seat and take some more detailed pictures tonight.

Thanks,

BD
Wisconsin