1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

03 St4s Won't Start. Any Advice?

Discussion in 'Sport Touring' started by indiecourier, May 14, 2017.

  1. My ST4s is refusing to start.

    Last ridden Friday before last, going absolutely perfectly.

    Tried to start it last Monday ..... turned over fine but wouldn't fire at all. Put battery on charge.

    Tried again on the Tuesday, no go and the battery died eventually. Ordered new battery.

    Battery arrived on Thursday, removed fairing and fitted battery (Motobatt with a few hours on charge before use). Lots of rotation, no firing. Pulled plugs out .... front pretty wet, rear dry.

    Charged battery again and fitted new plugs on Friday ..... stll no go. Rang Richard Llewelin who advised changing fuel filter.

    Yesterday fitted new fuel filter. No change. Tried red key. No change.

    So ..... any ideas, anyone?
     
  2. Could be scores of things; Try

    Main connector on LH side of bike and check fuses
    Check Earth close to crack breather
    Check ECU earth
    Swap round relays
     
  3. Any Power Commander fitted?
     
  4. No. But I've just sent you a PM.
     
  5. Do you know if you're getting a spark at all? Do you have any way of checking for fault codes?
     
  6. For what they cost, always worth trying the ignition relay.
     
  7. Don't just check that fuses are intact. Remove and reinsert each one several times to remove any light oxidation that may have formed. Also check each fuse is flat and not twisted. A twisted fuse will not make proper contact due to the severely reduced contact area.
    Above all don't do loads of things at once and then try starting the engine or you'll never know which worked if it does start.
     
    #7 Old rider, May 14, 2017
    Last edited: May 14, 2017
  8. Side stand switch could be dodgy . It was on mine .
     
  9. I've looked at the workshop manual and am still clueless about which relay is which.

    Could you describe the location for the ignition and fuel relays please?
     
  10. There are 4 relays on the ST4s. 2 below the top fuse box under the LH side of the top fairing. One is for the headlight and the other is the mail relay. You will know if the main relay has failed because hardly anything will work including the lights, instruments, dash lights, starter, fuel pump and sparks. Since your starter turns you can most likely rule out the main relay.
    There are a further 2 relays under seat. You will find them if you lift the plastic tool tray. One of these is for the fan and the other is for the fuel pump, coils and injectors.
    Firstly, does the fuel pump run for a few seconds at ignition on?
    If not swap the 2 relays round under the seat and try again. If it now runs the bike will probably start and the fuel pump relay is faulty (now in the fan position).
    If the pump runs at switch on and the bike won't start. You need to establish if it is sparking then we'll take it from there.
     
    • Useful Useful x 1
  11. As Derek pointed out, under the seat. Injection relay has brown & brown/white cables running to it usually.
     
    • Like Like x 1
  12. Thanks guys.

    On mine there are 3 relays to nearside of headlamp and one under the seat. The one under the seat is identical to 2 of the front ones andcertainly feeds the fuel pump ..... pump ceases working when I remove it.

    So I know the relay under the seat works and have now tried swapping this relay with the 2 similar ones at the front, all of which make the fuel pump work, ergo all are OK.

    I have tried a spare plug in the front plug cap earthed against the motor .... find it a bit awkward holding plug(cap) and pushing starter buttom but there are sparks although a bit intermitent due to my cackhandedness.

    Just had one gut wrenching thought ...... would it still spin over if a belt had snapped?
     
  13. The other "relay" under the fairing is in fact the flasher unit. The engine would still spin with a broken belt. It might bend the valves on the cylinder with the broken belt but should still start on the other cylinder. I doubt very much if a belt has broken but since there are both fuel and sparks then the engine should start. Are you doing anything with the fast idle (choke) lever? Best to start with it off and slowly move it forward as the engine cranks until it fires.
    A new pair of plugs might also help.
     
  14. Belts rarely snap.
    They can shred if badly installed or if slack enough, jump a tooth or two, putting the valve timing out, so valves contact piston, thus snapping the belt
     
  15. Having said that, someone on here recently had lots of trouble starting his bike, then when he came to replace his belts, he found they were incredibly slack, so slack it affected the valve timing,
    With the new, properly tensioned belts, it started beautifully.
     
  16. Are you switching the ignition off then back on again each time you press the starter. I'm sure the immobiser cuts in after 10 seconds or so when you turn the key.
     
  17. This - I got caught out by this when I first got mine. Even if you have the immobiliser bypassed and unplugged, if the ignition is on for more than 10 seconds the bike won't start.

    As it worked on the Friday, but then didn't on the Monday, it should be something fairly straightforward. As you say it has a spark, if it also has compression and fuel it should run.

    There are lots of things that it could be - are you able to scan it for codes to remove some of the guesswork?

    I have had an issue with a coil connector being intermittent that stopped it starting before now.
     
    #17 Turbogeek, May 15, 2017
    Last edited: May 15, 2017
  18. The spark, as tested by a fairly incompetent me with a spare plug held against the crankcase, does actually appear to be fairly random.

    So, after a very enriching chat on t'phone with Derek, I'm now fantasising that the crank sensor has gone tits up.

    So plan for today is to pop the belt covers off just to make sure that the belts are still in one piece and double chect the earth from the ECU (need to remove battery to remove the lead from the mounting bolt and do a continuity check).

    Then persuade a friend to come and witness the spark check ........ it'd be great if it was the crank sensor but probably far too sinple.

    And yes, I am aware of the need to press the start buttom pretty smartly.

    By the way ..... does everyone's bike keep turning the starter until the bike starts even if you take your finger off the button?
     
  19. I have an '03 registered ST4s (I guess it's technically a 2002 bike) and it doesn't have the auto-start or "Servo-Start" function. The only time mine continued to turn after I released the button, the starter solenoid had welded itself together!
     
  20. Ah! This one has always done this since I've had it, about 5k miles,

    It did need a new solenoid when I first had it but that was, obviously, about 5k ago.

    Oh well ... just another thing to worry about, eh?
     
Do Not Sell My Personal Information