Hello all,
I have an 85 K100rt I've been working on. Got it to the stage where I was ready to start it. The motor was turning but the fuel pump doesn't seem to be working. I got the motor to run off starting fluid. The tank had been sitting a few years with untreated gas so that may have something to do with it. I was just wondering if there was something that I was missing regarding the fuel pump.

Thanks,
Passion85

Passion85
You should hear a whirling or whizzing. If not have a peak inside tank and see if you have any black particles or goo laying in bottom of tank as mine had. On mine the rubber vibration damper that the pump sits in had disintegrated. I had both hard small rubber particles and basically goo or tar like material. This material got into the pump and seized the pump. If you don't see such material and the tank is clean then you are very lucky.
Unhook battery and drain or siphon fuel out. Remove tank fuel cover (4 Philips). Use flashlight and view the pump where you will see a white or yellowish plastic gasket that the pump fits in. On each side are squeeze tabs that you squeeze and can lift the pump and gasket out. Before you do this use 7mm socket and undo the full hose to top of pump. Now lift the pump out with wire intake and take out of tank. ....wires should come out easily unless they are hook around something...don't force. At this point you can reconnect battery and test voltage across the fuel pump wires when turning over bike to ensure you have power to pump. If you have approx. 12v and pump doesn't spin then pump is dead. If it turns stop immediately as the pump uses the gas as a coolant and you don't want to run dry when out of tank. If dead then remove the 2 electrical wires from pump. You will note that pumps has two different size connection posts to prevent mixup. Take battery lead off again.
You will note that I do all this testing outside of tank for safety reasons.
If pump is dead remove the bolts on the plastic gasket and pull out the pump and replace reversing install. Check the vibration gasket to make sure it is intake and not falling apart or showing issues. Check your fuel lines inside as well and also replace the fuel filter noting the arrow direction when reinstalling.
As I said before mine has black goo and particles and it took many frustrating hours of cleaning out tank with kerosene.
If pump is good you need to move on to checking spark and also the injectors. Injectors could be plugged. If they are then get them ultrasonically cleaned and new filter and o rings. This can be done at any diesel engine or industrial engine or fuel injection overhaul shop. I had mine done for $125 for the four.
Check service manual on this forum or web.

Good luck.

Thank you Bluenose.
Very descriptive! I managed to get the fuel pump out, unfortunately the rubber damper had completely disintegrated on the bottom and like you said turned into this terrible tar like substance that is incredibly hard to remove. The pump itself was shot, as was the the screen at the bottom of the pump. Looks like I have a little bit more to work on this project. Thank you again for the great information! Does anyone know what kind of fuel pump I need to replace it?

Do a search for 'fuel pump' on the forum.
There have been many threads on cheaper alternatives for the original Bosch pump.
A new rubber damper will cost you, though.
Don't forget to replace the fuel filter before you go out again. It will be clogged up, too.

Hi:
I had good luck ordering a new pump from ebay from UK at
http://www.ebay.ca/itm/271166989847?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649.
However it was not marked Bosch but exactly same and could therefore be a damn good knockoff. Works well so far.
Bobs BMW and various places have replacement and alternates as previously mentioned. Depends on how much you want to spend. I ordered the vibration damper gasket with cover shroud from local BMW dealer which turned out about the same price as internet. However they only had the cover shroud (filter screen) with nipple which had to be cut and modified to fit. My machine took the earlier shroud.
Various ways to go on the pump as you will learn from the forum.
While you are at it, or perhaps before you order new, take the pump apart (use plier to pull back crimps at top and pull apart). (before you do this look at bottom inlets and see if you can see the yellow and black crap which is first indication you are seized) Your pump is probably just seized with goo and electrically ok. Carefully photo everything and note order of bottom pump section when taking apart and don't drop washers or screws. Soak parts in cleaner and pick off shellac and tar. Sand with very fine paper if you have too but just enough to get stuff off and put all back together. Drop into can of gas and hook up 12 volt....it might work as mine did! I had to coat the top with epoxy to seal the unit back up. You can also test PSI with manometer if you have one. My pump now serves as backup. You will also find procedure on line.
I can send you photos but there are better ones on forum and internet. Let me know.

Good luck.

Passion84
Here is the link to Crazy Frogs cracking open the fuel pump. I sure wish I had stumbled upon this prior to my go wild method! Excellent descriptions and photos as usual from the guy across the harbour.

https://www.k100-forum.com/t1068-opening-the-fuel-pump#5662
You will not go wrong with this method.

Bluenose

Hey guys sorry it took so long for me to respond. Unfortunately Bluenose I went for the wild and crazy method and accidentally cracked the aluminum casing on the fuel pump. I think the pump was already bad anyway where the brushes contacted the copper on the inside it had worn unevenly. So I went to work trying to find some replacement parts. I was able to find a fuel pump on eBay that had the same psi and output for only about $40. Next I found a replacement damper and a sleeve for the new pump to fit snugly. I have a question about this new pump, where the leads hook up to the old pump they were held in place with a nut, this one only has leads where the leads could be shoved through. I was wondering if there would be a good way to secure the wires to the new pump. I think I attached some pictures but I wasn't a hundred percent sure how to go about it. Any help would be much appreciated.

Thanks,
Passion85
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Just make sure the connectors are tight when you push them on and you should not have any problrms. I have them on the pump on the K1100 and would not expect to have any problrms.

That pump should work fine, just use any electrical crimper to change the connectors over to the spade type.
Don't forget the filter basket.

My replacement pump had a connection block to match up to the connection block on a car. I pulled it off and soldered the wires to the small male connectors with push connectors on the other end of the wire to connect to the bike wiring. I couldn't get a proper fit otherwise. I think standard connections should work fine on yours.

GMcQ

Regarding the fuel pump replacement I was online with a new fellow last night and he has had great success using a Ford Bronco II pump. Says its a drop in replacement. I don't have any experience with that one but maybe the next one on the fuel pump quest can advise.

club_c wrote:Regarding the fuel pump replacement I was online with a new fellow last night and he has had great success using a Ford Bronco II pump. Says its a drop in replacement. I don't have any experience with that one but maybe the next one on the fuel pump quest can advise.

Quite likely right as it is the same era as the mustang pump from the 5lt V8.

Hey guys! I got the pump to work by wiring it hot to the battery. The output was more than enough to keep up. I've heard that the bronco fuel pump could work as well. I found this one online for pretty cheap (I think this one was originally made for a 99' Ford Taurus) and it had the same output and the foam spacer was pretty cheap. I was able to solder a wire ring terminal to the terminals on the pump. Now my fuel level sensor has lost continuity and I don't trust my wiring skill enough to replace the diodes inside of the sensor, thankfully idjman has a sensor he is willing to sell me! Thanks for all the help guys!!!

Thanks,
Passion 85

Oh and the pump came with a 6 micron pre-filter which I think might be better than that dang basket that was already in the bike, it seemed pretty iffy.

Thanks,
Passion85