Hi,

I have multiple problems due to dirty petrol and damaged fuel pump basket filter. The gauze was torn in several places. Initially this lead to the pump locking up due to some dirt in the pump. Having got it working I still could not start and noticed that I had a return of fuel to the tank when I initially applied power and the pump never got to the cut-off pressure as it should.

I think this must be due to some dirt also getting stuck in the pressure release valve.

I have an ultrasonic bath but if a bit of dirt is stuck in the valve with the pressure of the spring on it, I doubt this will just fall out.

Anyone know a trick I can try to flush the obstruction?

Many thanks.

My understanding is that the pump doesn't have a cut out pressure switch, it runs all the time.  The pressure at the injectors is controlled by the pressure regulator and the flow returning to the tank is perfectly normal. 

If everything is working properly, the pressure should be approximately 2.5 bar.

While attempting to resurrect an R1150GS which had been crashed then left out in the rain for three years (fuel turned to furniture polish) I deliberately connected the fuel pump (removed from tank) backwards and with short voltage bursts, accompanied by squirts of carburetor cleaner, burped out the obstructions. That pump still hums in the machine. It was 2013.

thanks two-wheels.   I did flash the pump as you said, but it required a bit of mechanical poking too.  It seems fine now.

@.75 :  when I turn the key the pump normally runs for about 1 or 2s before stopping.  I assumed that was a pressure sensor, but thinking about it, it may be a timer. If I flip the starter button , but not long enough to fire up the motor, it similarly just runs a sec or two.

Whatever the reason, this is not what is currently happening. If I turn the key without hitting the starter the pump is running continuously , with return flow to the tank. This is not normal operation.


This arvo, I pulled out the FPR and, blowing into it, there was a leak. I put it on the compressor and it made a sound like an air horn. I figured that would shake out whatever was there, It did.  Blow test was now air-tight.

Back on the bike , still constant running but the impression by ear ( pump slows as pressure builds up ) that the pressure was getting higher.

Can anyone confirm the control mechanism at key-on?  Is the fuel control unit supposed to cut the pump after a second or two , or is there a pressure sensor?

TIA.

Beamer wrote:Back on the bike , still constant running but the impression by ear ( pump slows as pressure builds up ) that the pressure was getting higher.
 

If you have removed then reinstalled the tank, check that you have the delivery and return lines connected to their correct ports.

Please put your moto's year of manufacture and its model number in the bikes* box in your Profile. It will then appear below each of your posts.  That lets readers know what model is under discussion. Models can have differing system characteristics according to year of manufacture and model type.

The pump will run for 1.5 seconds after the start button is released but will keep running if the hall sensors tell the ICU that the engine is running.

It sounds like your bike has a Jetronic ECU.  The fuel pump is powered by a fuel pump relay that is energized by the ECU.  When starting, the ECU sends a pump signal to the fuel pump relay when the start button is pressed.  If the engine doesn't start, the signal lasts as long as the button is pressed plus 1 second. 

If the bike starts, the Hall Effect crank rotation sensors send pulses to the ECU that tell it that the engine is running.  The ECU then keeps the fuel pump relay energized to supply fuel for as long as the pulses keep coming in.

If your fuel pump keeps running when the engine isn't, the first place to look is the fuel pump relay to see if the contacts are stuck in the closed position or if it is always being energized by the ECU. 

Pull the relay and check the resistance across the normally open contacts.  There should be an open circuit across them.  Then with the ignition turned on, check to see if there is 12V across the sockets in the relay mount for the relay's coil connections .  That will tell you if the relay is being energized by the ECU when it should be off.

Thanks .75,  I think you may be right about checking the relay. I have new ones ordered but I replaced it with a s/h one and did not check it thoroughly enough. Silly.

I'm assuming the initial turn-on energisation should be the same as blipping the start button, so that does suggest the relay is welded on. 

laitch wrote:If you have removed then reinstalled the tank, check that you have the delivery and return lines connected to their correct ports.

Very good suggestion. I hope I'm not that senile yet !

BTW this is the K75C, with Jetronic . Sorry for failing to specify what I was referring to.

The K100/K75 wont start the fuel pump when the key is turned on only when you touch the start button.

OK, thanks Rick, my bad recollection. It's pretty clear the relay is jammed then. I may have time to swap it later. I'll get a pressure gauge on the fuel line too.

thanks for the heads up.

If you swapped relays, you may have installed one with normally CLOSED instead of normally OPEN contacts.  That could cause what you are experiencing.

Beamer wrote:

laitch wrote:If you have removed then reinstalled the tank, check that you have the delivery and return lines connected to their correct ports.

Very good suggestion. I hope I'm not that senile yet !

It doesn't take any degree of senility to do that. It takes distraction, and that can happen regardless of age. You wouldn't be the first to have done it.

Point-Seven-five wrote:If you swapped relays, you may have installed one with normally CLOSED instead of normally OPEN contacts.  That could cause what you are experiencing.

Another good point there ,  .75 , I did not even consider that. I'm being very slack. That would explain why it is failing to start too, since every time the Hall picks up it would cut the fuel pump.

I think you hit the nail on the head there. Many thanks.

Let's hope that's what it is.  Easy fix.