BMW K bikes (Bricks)


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Rochen

Rochen
active member
active member
Hello everyone,
Let me give you a bit of context. Last Saturday, I went on a ride with my 1986 K100 8v motorcycle, and after about 15miles, the bike broke down on me. The symptoms were similar to fuel starvation, as if you were running out of gas.

Over the past few days, I've been testing and checking things, and here's how it went:
  • First, I checked if the spark plugs were producing a spark. I also tested each spark plug with each spark plug wire, and all possible combinations produced a spark. So, I've ruled out spark plugs, wires, and coils.

  • Second, I checked the injectors. It seemed like there was fuel coming out, but very little. I removed and cleaned both the injectors and the injector rail.

  • I also checked the air filter just in case, it was a bit dirty but nothing serious.

  • Finally, I removed the fuel pump, connected it directly to the battery terminals, and it was pumping fuel well, both with and without the fuel filter.



Upon removing everything, I noticed that there was this filter, is this the correct one?


Problem - no power to the fuel pump GUdXqZN

Then, while making sure the fuel pump was working properly, I connected it back, but there was no sign of movement. I tested it with a multimeter, and there's no current reaching it! No wonder isn't working. Do you know what could be the issue? Fuel level sender? Check the wiring?

On another note, while searching for information on the forum, I found that you can bridge fuse 6 of the pump with the positive terminal of the battery, and there should be movement. However, there's complete silence.


And one last question, I've taken a video inside the tank. It seems like there's some debris but not too bad. However, I couldn't identify the fuel level sender. Instead, I saw 2 wires that go directly from somewhere to the pump.


Thank you very much, everyone. I've attached the video.

Fuel pump function

Interior fuel tank



PS: I also checked the fuse for the pump and it's ok

    

Suzi Q

Suzi Q
Life time member
Life time member
Check all the hoses inside the tank for splits.
Check the electrical connector to the fuel tank - under the front left hand side - I think yours might be the 4 pin circular type which are prone to poor connection. If that is the case then BMW thoughtfully provided a 'spare' 4 pin plug in the relay box (which is actually an accessory connector) you can cut this off and use it to replace the original.


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

Dai

Dai
Life time member
Life time member
Yes; the connector is the most obvious problem. The connector has female pins inside it, so you can try using a very thin screwdriver to get between the outside of the pin and the wall of the connector, then twist carefully to close the gap in the pin.


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

Rochen

Rochen
active member
active member
You are the best, you are both right. It was the round connector under the tank.

I have been touching it to verify and it has already fallen, I have seen that it is very loose and I will carefully try to close the pins more so that it makes more force.

Thank you all very much since I had missed checking that connector. Finally it has gone "okay" so I have been able to review and clean several things on the bike that always comes in handy

Regards!

    

92KK 84WW Olaf

avatar
Life time member
Life time member
Rochen wrote:You are the best, you are both right. It was the round connector under the tank.

I have been touching it to verify and it has already fallen, I have seen that it is very loose and I will carefully try to close the pins more so that it makes more force.

Thank you all very much since I had missed checking that connector. Finally it has gone "okay" so I have been able to review and clean several things on the bike that always comes in handy

Regards!

Some time back I bought a few of those plugs from Tills.de as I have 3 running early Ks with those plugs on them. Worth buying a few sets.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 48,061 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 61,190 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

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