[AschwinVDM]

Normally the bike activates its fuel pump for about 2 seconds when you put the key switch to "ON",
so when you press the ignition button fuel pressure has already been build up.
My bike no longer does this.
It only starts the pump together with the ignition button en keeps running fine as long as the engine is running.
There are no active fault codes (using a gs-911 diagnose tool to read)
The pump also runs fine when activated manually (using test mode from the same gs-911)
It's been like this for the last 10000 km's and doesn't change.
The bike runs well, but it just takes 1 to 2 useless (extra) cranks to start it because it still needs to build up fuel pressure.

Anyone who has an idea why?

 

[ero__]

Fuel Pump Controller Board

Yeah. That's it. I've made fuel pump controller from zero with original equivalent parts of course. I live in Istanbul/Turkiye and I can send it (only board) for €50 + postage if anyone interested in. :)

www.f800riders.org

 

[AschwinVDM]

Yeah but why does the pomp still work when the bike is running?
Shouldn't a broken controller cause trouble all the time?

 

[ero__]

Some short circuit may do this, or someone (old owner) make a connection directly.

 

[ThiagoSilva287]

Normally the bike activates its fuel pump for about 2 seconds when you put the key switch to "ON",
so when you press the ignition button fuel pressure has already been build up.
My bike no longer does this.
It only starts the pump together with the ignition button en keeps running fine as long as the engine is running.
There are no active fault codes (using a gs-911 diagnose tool to read)
The pump also runs fine when activated manually (using test mode from the same gs-911)
It's been like this for the last 10000 km's and doesn't change.
The bike runs well, but it just takes 1 to 2 useless (extra) cranks to start it because it still needs to build up fuel pressure.

Anyone who has an idea why?

There can be several reasons like clogged fuel system, old fuel, bad battery, inactive motor or stuck valves so on. To avoid such issues motorcycle need proper analyses and look after.

 

[Pat H]

I would expect the fuel pump to operate in such a way that it doesn't run if the engine isn't running to prevent a fire in a crash. However as you say it needs to prime when first powered up. so the pump regulator will have 2 functions. One to supply a variable power supply (so the fuel line pressure is stable) to the pump while the engines running. And then a second function that allows the pump to run on intial power up for those few seconds. Seems that second regulator board function has failed.
Just replace the fuel pump regulator.

 

[bmwroadsterca]

I would expect the fuel pump to operate in such a way that it doesn't run if the engine isn't running to prevent a fire in a crash. However as you say it needs to prime when first powered up. so the pump regulator will have 2 functions. One to supply a variable power supply (so the fuel line pressure is stable) to the pump while the engines running. And then a second function that allows the pump to run on intial power up for those few seconds. Seems that second regulator board function has failed.
Just replace the fuel pump regulator.

The pump controller has no way of knowing the fuel pressure. The controller just translates the low power PWM logic level signal from the BMSK to a PWM signal capable of driving the pump. There is a fuel pressure sensor in the fuel rail. The BMSK uses the sensor's input to decide if pressure needs to be regulated up or down. Whether the pump runs or not is decided by the BMSK.

 

[Pat H]

I didn't go into the detail of how the pump regulator gets its info to control pressure but control the fuel pressure it does.
So either the BMSK should be sending a PWM signal at power on to drive the pump for those first few seconds and is failing to do so (unlikely as it clearly does what it should when running) or the BMSK does nothing on ignition on and doesn't start sending PWM signals till the engine runs. In which case its still a seperate function in the pump regulator to do those first few seconds of pumping. I'd still go first to the pump regulator.