New day, new problem.  When I turn on the key and hit the start button on my 1985 k100 RS, the fuel pump doesn't get primed so the bike won't start.  I can make it work by running a wire from the + terminal on the battery to the left hand pin side of the 6th fuse.  It will then start and run for a few seconds.  I have checked voltage to the right pin side of the 6th fuse and it is getting voltage when I hit the start button, however, it's a quick jolt of power and my meter is only reading up to about 9-10 volts.  It's hard to say if it's my volt meter that is reacting to slowly or whether or not there isn't actually enough voltage arriving to start the pump.  I've put my finger on the fuel injection relay and it's definitely activating when I hit the start button.

Is it reasonable to think that perhaps the relay has dirty contact and isn't transmitting enough juice to start the pump?

Any other ideas??

Your help and thoughts are appreciated.  Thanks in advance for responding.

PS.  new pump was installed only two years ago.

Yours is a 2v engine and the pump does NOT prime, it does NOT run when you turn on the ignition. No power at the pump is correct.

It WILL run or should run when you press the start button. You now will have power to the pump.  It will stop when you release the start button. If it stays running as long as the start button is pressed [hold it down for a few seconds] you have a good pump circuit.

For the engine to stay running it gets a second signal from the Hall Effect Sensor HES to keep the engine running. If this is an issue check the big plugs, into the Fuel injection Control Unit FICU under the seat and also the Ignition Control Unit ICU at the headstock.

I know this already and do state that I "hit the start button".  Nothing to do with the hall effect sensor either as I changed it two years ago when I changed the fuel pump.

jumpinjimmy wrote:I know this already and do state that I "hit the start button".  Nothing to do with the hall effect sensor either as I changed it two years ago when I changed the fuel pump.

12V is needed. The meter should record it. If you haven't replaced the fuse, do that but clean its receiving sockets with emery cloth and contact cleaner before installing it. The battery should be in the 13V range to be in optimal condition.

Battery is 4 years old and probably should be replaced but I recently did put a charge on it and it turns over very well but still won't start on its own.

jumpinjimmy wrote:Battery is 4 years old . . .

Check its voltage and do the fuse thing. We're at the last and best of riding season for these two months here.

will do, but I believe the problem is deeper.

jumpinjimmy wrote:will do, but I believe the problem is deeper.

I don't let belief get in my way. Action is the thing.

I'll let you know the result

jumpinjimmy wrote:I'll let you know the result

10-4

no luck on cleaning the fuse and fuse contacts but thanks for the advice just the same.  I did, however, find the problem by removing the FI relay and taking off the plastic cover and cleaning the contacts.  It immediately fired up the fuel pump when I hit the start button and the bike started right away.

Thanks all, problem solved.