Cold starting issues

[Simon-GS]

As the mornings are getting a bit colder I have experienced a small problem with my 2008 GSA.
After I have been riding a minute or two, when i pull the clutch in at the end of my road sometimes the motor just dies, once it does its a bit tricky to start.

It only seems to happen if the temperature is below 5C. I have plugged in my GS911 and it shows no faults. I have checked the TB balance and it looks almost perfect. I didn't check valves clearances but I assume if the TB balance is Ok then valves cant be too far off.

Any ideas what might cause this? I feel like it needs to idle a little higher when cold but there is no adjustment for idle speed. Maybe I just need to start the engine before moving out of the garage so it warms up a little before riding off?

Thanks.

 

[Mistacat]

Plug the GS911 back in , Look at real time values and check that the inlet air temperature sensor is reading the right sort of value.
If OK you might start checking secondary coils by unplugging the LT side on each one.

 

[Pukmeister]

Seeing as you have a GS911, check the output of your throttle position sensor at 0-100% in real times values and also try resetting your idle stepper motors using the calibration facility.

 

[Bendy toy]

Mine did this when I removed the fuel strip.
The strip reading empty runs the fuel pump at full power. No strip runs the pump at normal power. My pump is weak so normal power at the pump couldn't fully empty the fuel tank.
We'll see if the new pump solves the stalling and tank emptying.
I don't have a 911 so can't check fuel pressure.

 

[Mistacat]

The GS911 will not give you a fuel pressure reading.
I may well be wrong but I was under the impression the the fuel pressure regulator is purely mechanical.
Also where are you obtaining your fuel pump running data from as the GS911 and a direct feed to the BMSK only show pump on or off.
I realize that this is the feed to the pump controller, are you getting your pump control voltages post controller and what are they and under what conditions.
Apologies if this has drifted off post, Just interested.

 

[Bendy toy]

I have no idea what my actual fuel pump pressure should be but I do know it's low because there is not enough return flow to drive the venturi pump which moves fuel across the tank. (up to 2 gallons of fuel can get trapped on the RHS)

There is a very long thread on sdvrider that discusses fuel pump issues. Along with my own experience I worked out -

• The fuel pump controller sets a mark space ratio for pump operation this minimises pump load while providing adequate pressure at the injectors. There might be a feed-back loop to adjust the pump to demand but I suspect not.
• When the fuel tank is low (probably below 25%) the fuel pump is run at a closer mark space ratio. This makes sure the tank right hand side is emptied.
• A weak fuel pump will leave fuel in the tank RHS because it has too little return flow to drive the venturi.
• A weak pump might cope with the tank emptying if it's run at full power.
• People who fitted new pumps solved the tank emptying issue.

I have fitted a new sliding float type fuel gauge with separate head unit. It uses the standard 10 to 180 Ohm scale. I removed the old fuel strip and immediately ran into issue with the tank not fully emptying. I had previously had a rough tickover and some hunting despite the throttles being correctly balanced but only spotted a possible connection in hindsight.

The colder weather has caused more stalls a minute or two after starting. It always restarts but annoying. The tickover is consistently lumpy.

My fuel strip failed at least 18 months ago. Ever since, the tank has read empty so the fuel pump has been running flat out all of the time. removing the fuel strip put the pump back to normal mark space ratio which cant deliver enough flow to empty the tank. Ive not proved the point with a controller bypass but I don't believe the tank emptying issue and lack of fuel strip were coincidence.

I have not yet used the bike but starting with the new pump it ran and ticked over much more smoothly than I'm used to. I'm using it today so we'll see how it goes.

I believe it might be possible to use a sliding float gauge to drive the bike's own fuel control system. Also on advrider there is a spoof circuit (using a 2K resistor) that causes the gauge to show tank full all of the time. At some point I will set up a test with variable resistors to see if I can create any indicated fuel level.

 

[Simon-GS]

Thanks for all your replies so far.

My fuel strip was failed when i bought the bike, no idea how long it was showing empty for. I flashed it and it works now. Maybe the pump running at full capacity has damaged it somehow, which now shows my issue? Maybe I should disconnect the fuel strip and see if it improves my cold running? My idle isn't rough, its just the cutting out which is annoying, even today with temperature about 11C I felt that it was very close to stalling until it warmed up a little.

I plugged in my 911 this morning and air temps seems reasonable, re-calibrated idle stepper motors, forgot to check throttle position. Will do that tonight. Didn't look at coils, maybe I will play with those tonight too.

 

[Bendy toy]

My bike has >60K on the clock, but I believe the OEM fuel pump life was shortened by running it always at full power. When the strip failed I had no idea how the system works.

The bike started just the same this morning but didn't stall. However the weather is warmer today. On the plus side my fuel tank was low so I could do the job, but the gauge reading went up after a few minutes running, so its likely the venturi is now working. I have a spare fuel can so will run it dry and check the miles. More than 300 will mean it's properly emptied the tank.

Cutting out more often could be a primary coil. The old back type are not very reliable and when one fails the other will be along very soon after. Mine (actually smelled burnt) were replaced with stainless sheathed type. I still have the OEM black secondary coils.