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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: gag1025 on January 15, 2018, 04:04:59 PM

Title: My 1992 K75 Will Not Start
Post by: gag1025 on January 15, 2018, 04:04:59 PM

My question is how do you (without taking it out of the tank and hooking it up to a battery) check the fuel pump to make sure it is operating properly. My 1992 K75 turns over, has good fire but will not start. I replaced the battery a month ago, cranked it up and let it idle for a few minutes before I shut it off. Last week the weather was warm so I decided to go for a ride but it would not crank. It turn over great but will not fire up. I checked the plugs and fuel pump fuse. All are OK.

Title: Re: My 1992 K75 Will Not Start
Post by: jakgieger on January 15, 2018, 06:18:04 PM

I can hear mine running...but have the tank lid flap removed and can visually see the pump as well.  I would think that you could arc the pump at the four pin connector.

Title: Re: My 1992 K75 Will Not Start
Post by: Martin on January 15, 2018, 06:25:47 PM

You could try pulling apart the 4 pin connector. Check power at the green wire brown is the earth, while hitting the start button. This 4 pin connector is a known problem of the fuel pump failing to operate. I have just replaced mine after no problems after twenty years then all of a sudden it started to play up. DeoxIT can sometimes fix it, otherwise replace with a quality waterproof one. If you have power on the output side of the 4 pin connector you can try applying + power to green and - to the brown wire gong into the pump.
Regards Martin.

Title: Re: My 1992 K75 Will Not Start
Post by: alexg on January 15, 2018, 08:55:55 PM

I would start by making sure the battery is fully charged. Also, take a plug out and see if there is fuel on the plug. If you did not let the engine run to temperature, it could be that leaky injectors flooded the engine. It does still happen in cars that have 1/4 of the age as these bikes.

Title: Re: My 1992 K75 Will Not Start
Post by: Laitch on January 15, 2018, 11:52:59 PM

With the ignition on, press the starter button. When you release it you should hear the pump running for a few seconds. Remove the six-screw fuel cap assembly. When you push the starter button you should see agitation of the fuel coming from the return line. That will tell you the pump is working but not how well it's working. Measuring its pressure to and from the fuel pressure regulator with a gauge that has an appropriate scale on its dial will indicate how well it is working.

While the tank cap assembly is removed, how clean is the fuel tank and what is the condition of the rubber vibration damper that holds the pump within its mount—gooey or firm?