I have a 2006 ST3S which has recently started to peter out, usually at lights for maximum inconvenience! It seems to happen after a longish ride on open roads, when having to stop at lights. Holding the throttle open makes no difference. The coolant temperature is fine and there are never any errors logged. It has just had a new fuel filter and the tank cleaned. If left for a few minutes it is ok again for a while before cutting out again (usually at the next set of lights )…. The tank is rusty inside and there has been water in the tank before. I have been using E10 fuel, but have just tried E5 on this tank. The only other thing of note is that the issue seems to occur after around 180-190 miles on a full tank. However, there is plenty of fuel left and the bike hasn’t gone onto reserve at this stage. If left to go cold, it starts and runs perfectly the next day as if nothing had happened (without having filled the tank). I have checked the breathers and tank cap and gone through all electrical connections with IPA, no corrosion on the connectors. The bike has recently had a new fuel pressure regulator and the throttle response is great (normally)…. Any ideas gratefully received!
that's a difficult one, and nothing you haven't tried comes to mind yet. When you did filter did you change hoses also? I know you said you've checked breathers but quick test for me to confirm is just to open filler cap slightly straight after it peters out and then try starting immediately.
Thanks, yes hoses inside tank replaced. Have tried even re-starting with the cap open when it is doing this and still won’t start. Have wondered if it is the fuel pump diaphragm? Not even sure if it has a diaphragm?? I’m reasonably sure it isn’t electrical or electronic, as the ECU seems pretty comprehensive in terms of the number of sensors and the fact it doesn’t show the engine management light when this happens….
so it looks as though starvation related to tank breathing can be ruled out then. Are the symptoms identical both before and after changing filter and hoses? Does the fuel pump tone sound the same both when you start up as normal and when you are experiencing the problems starting?
It’s a weird one - it first happened in September last year when we went to the north coast of Spain. Around 3.5 hours on the motorway, no issues, then in the town we were staying in, after a few sets of lights it refused to start and had to be pushed to the hotel! The next day it was fine, as if nothing had happened! This was before changing the filter and pipes in March this year (filter had been changed months earlier twice due to the crap in the tank). The problem didn’t happen again until this March immediately after the filter and pipe change. Again it was fine for 180 miles, then played up at lights . Since then it has started to happen fairly regularly, but not always. It happened last Saturday, then after a couple of hours ‘rest’ and without filling up etc it was fine for the rest of the journey…..Makes anything other than open roads a bit unpredictable…. Occasionally it will cut out between gear shifts when hot, but restarts…. When it peters out it won’t restart immediately but will if left for several minutes, then it does the same thing again. Any possibility of immobiliser issues??
Re:- "Any possibility of immobiliser issues??" I don't have long enough recorded memory experience or enough "electrical competence" in this area to help with above, but I think you would get other electrical symptoms accompanying this if it were the case. Have you crudely tried a slave plug to check for spark straight after it peters out/won't restart? I think I would check for lack of fuel and if confirmed then replace all feed and return lines to injectors if necessary.
I had my hands on an ST3s a while back which had similar problems to you, sometimes the bike was fine, other times it would just stop, leave it for a while and it would run again. Diagnostics indicated a memorised fault in the fuel pump relay, ie there had been a problem but the problem wasn't present at the time the diagnostics were plugged in. The relay was the original one. It looked OK and worked when power was applied to it off the bike, however, I suspect it was intermittently failing internally. A new relay was fitted and the problem disappeared.
