Also, if it hasn't been mentioned... put a smear of clean grease on the (preferably new) o-ring and on the inside lip of the fuel plate hole. Prevents twisting, leaks, curses, etc. You may also find the plate bolts no longer reach their respective holes when you go to install. Grab three M6 x 20 bolts (longer than oem) and you'll find you can evenly and smoothly pull the fuel plate back into the tank. Replace when you have a half inch or so left with the original bolts and screw them down flush.
It had been riding ok yes - but then I saw the jet going across inside the tank and panicked! So have I removed the pump for no good effing reason??
probably ok! re: removal, I don't think you have wasted your time, you must be "warm" and although i've never seen the squirting air separator, if you have fuel squirting at such a rate that it can leave the tank through the filler, i'd say something is wrong. Sometimes an oversize fuel hose gets used which can cause a pressure leak. It's worth checking all hose fixings as they should be "snug" - see how easy it is to swivel hose on filter/fuel junctions.
I will give it a good look at tomorrow - nothing obvious so far and all joints were pretty tight - not turning! Can 916 owners go start their bikes, open the petrol cap and see if they can see anything squirting about inside!! Take a pic and let me know pls!! Cheers all!
Yes, the return fuel from the injectors can come out of that nozzle, I’ve seen it before. See post #4 above Yes you can reuse the green viton o-ring if you are really careful Going forwards, when/if you order a new o-ring get 2or 3, it’ll cost you no more in postage and you’ll always have a spare to hand
Take a look at this FB group post, there’s a video of what you describe. https://www.facebook.com/groups/46064396229/permalink/10157532441896230/ It’s an ST4 but the fuel circuit is identical to yours.
right, needs i've never seen fuel returning at that rate on a Ducati at idle, it would be good to get someone else to comment but generalising here, this can be due to a partially blocked or malfunctioning injector among other things.
Yes that's what mine was doing although with much more force! ie when I opened the filler cap I got showered - the jet was going in same direction as that video but harder and causing the fuel to spray out! Thanks for that - good evening wasted removing shit that wasn't broken
Christ - even that FB video in the comments no one is sure!! Not normal, yes normal! Think I'll just put it back together tomorrow and go for a ride - if it breaks down - we know there's a problem!
I would also go with the theory that is a dodgy injector thats causing more of the fuel to be returned to the tank rather than squirted into the cylinder. Might be worth pulling plugs to see if one is running leaner than the other, could indicate which maybe not flowing as well as it should.
I suspect it was that obvious in that short vid Chris as the tank was almost completely empty. In your case, did you have fuel in the tank? A lot more than in that vid at any rate? You may have got showered from the return fuel squirting into the tank of fuel and causing splashback . I feel for you for your wasted efforts , hence I was trying to flag it may not be a split fuel pipe early on. None of us really make a close inspection of what’s going on in the fuel tank whilst the engine is running but there’s a circuit for the fuel that goes fuel tank, pump, filter, injectors, fuel tank. The pump runs on key on up for a few seconds then stops. This is to pressurise the circuit and to squirt a minuscule amount of fuel into the throttles to prime them. As soon as the engine starts running the pump then runs continuously in order to maintain a constant pressure at the injector valve, around 3bar iirc. The excess fuel, and there will be more at tickover than at 10k rpm is dumped back into the fuel tank to be sucked back up by the pump again. If you have a split pipe inside the tank between pump and filter or filter and outlet pipe then the pressure will not be where it should be and whilst the bike might start it will struggle to rev to its fullest extent due to the low pressure at the injectors. If you have a split pipe outside the tank you’ll know about it straight away. Its unlikely you have a fault within the degasser unit itself (the off white plastic part). I believe what you witnessed and what’s shown in the vid I linked to is the degassed, excess fuel being squirted back into the tank. If it were my bike, I’d take it out for a spin, use the full rpm range and see if there’s any obvious fuelling issues. If not, then worry no more about it
"None of us really make a close inspection of what’s going on in the fuel tank whilst the engine is running but there’s a circuit for the fuel that goes fuel tank, pump, filter, injectors, fuel tank." Best speak for yourself on the first Paul, some of us had to do it for a living the circuit you describe has been around since at least 1972 from my own experience and probably earlier in other people's. As said, not sure that that is correct (fuel spraying at such a rate) but will be interested to learn if it is, on some models, but have looked in many tanks with less than half empty tank over the years, for sure, and i've not seen this, at this rate. Never had an ST4.
This could be standard Paul, with some combination, mostly evident with engine ticking over, I am rusty here, but in general, larger injectors, different mapping and of course twin injectors per cylinder would all have a bearing on this wouldn't they? and this is apart from things going wrong.
