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View Full Version : mysterious (and possibly fixed) fuel starvation problem


the_adam
24-04-2012, 08:19 AM
I'm asking about a problem that appears to have fixed itself here, just because I don't really trust it not to go wrong again :chuckle:

Background to it is that the bike had been running badly on the second half of my commute every day (so after about 20-30 mins, once things were completely warmed up or possibly just because this is where the traffic always is!). It would occasionally stutter when riding at lower revs, just lose power briefly but then carry on running as before. I think it would also do this at higher speeds, but it was much less noticeable. At the same time I'd often get either a hissing noise from the left side of the airbox (sounded similar to a quick release of air from a tyre), or occasionally a mechanical clicking noise from the right. I also found the exhaust was pooping a lot more with engine braking and getting the occasional random backfire, I haven't made any changes but assumed that the fueling was somehow slightly out and just wanted setting up properly

One day last week the bike refused to leave a petrol station. Starter motor was turning over but the bike wasn't starting up. My first thought was to check the fuses (I don't know why, but it's nice and easy to check :)) Having removed the ignition one and reseated it the bike started up fine. So all happy and I got home, just assuming that it had just been a loose fuse and everything was fine. I had an incredibly near miss with a car later that afternoon which really made me forget about it

Then on sunday the same thing happened, except my fuse trick didn't work this time :D It seemed to be a fuel starvation problem, it would run fine with easystart sprayed into the cylinders but then cut out again immediately afterwards. Fortunately I happened to be at the house of someone with a van and after we failed to get it working Ducati John kindly agreed to find time for it yesterday. He found nothing wrong at all, although by the time we got it to him the bike was mysteriously running again - I was only having trouble when the bike was fully warmed up so decided it was worth getting it checked over anyway. Whatever he did while checking it seems to have cleared the problem for now, it managed a long test ride yesterday without any trouble and it's been fine on the way to work this morning (will see how it is through traffic tonight...).

I'm just curious what could have been/be causing it...seems to me that something that shouldn't be there was expanding as the engine warmed up and partially blocking the flow of fuel, which was also enough to stop it firing when starting from warm. Just hoping that whatever it is has been permanently dislodged now :)

the_adam
24-04-2012, 08:22 AM
the exhaust was pooping a lot more

I really need to proof-read things before posting them... :chuckle: Should read "popping"!

Sirc
24-04-2012, 08:46 AM
I shouldn't worry - we all make mistakes let's faece it

Xenocide
27-04-2012, 10:53 AM
Check fuel lines for cracks/holes/etc. Is it the standard filler cap? Check that for sludge etc, if it seals completely it'll create a vacuum not allowing any more fuel out.

the_adam
27-04-2012, 11:25 AM
Yep, that all seemed fine, we were messing about with it for over an hour before we gave up and put it in the van :chuckle: It's been doing its usual 90 miles a day since then with no problems at all (other than the speedo bracket snapping :eyepopping:) so I'm relatively happy with it now

Xenocide
27-04-2012, 11:30 AM
*shrug*

I love your signature :)

the_adam
27-04-2012, 12:08 PM
I was planning to come up with a few of these and rotate them...haven't managed to think of any better ones yet though :D

the_adam
01-05-2012, 08:53 AM
Afraid it's playing up again, same running problems when it warms up (although it hasn't refused to start just yet :)). Still runs reasonably well until it's been on the motorway for half an hour

Think I've found the source of the "occasional low rev hissing noise" - I've only gone as far as opening the airbox up but it seems to be exhaust gas coming out of the inlet that goes down to the injectors (didnt think to check which cylinder but it was the inlet at the front left). Only happens at the right rpm and just for one stroke, which loses power for the duration of the (short) hissing noise then carries on as normal for at least a couple of seconds before the next one, similar symptoms to when I'm riding it. Whatever it is I don't think the fuel starvation problem would be doing this, but it can't be good...any thoughts? :eyepopping: My thought was possibly leaking gasket but I guess potentially something much more expensive if the cylinder has warped or anything.

It's got me questioning whether I should risk the trip down on saturday, it's not fun to ride and with 2 breakdowns in as many weeks I don't really want to end up stuck at a random service station...at least going to work on the m62 I know people with vans that can help if anything goes wrong. Saturday's also the only day I could really get it looked at...but i want to come :hissy: Going to have to think about this :scratch:

Nottsbiker
01-05-2012, 11:49 AM
Go to your nearest Ducati dealership and get a new bike out on a test ride, then pop down on that ;)

Xenocide
01-05-2012, 11:49 AM
Could you check spark next time i happens? Carry a spare plug about incase it's the coils breaking down?

I hate intermittent problems!! Good luck regardless!

Saint aka ML
01-05-2012, 11:53 AM
That exhaust smoke is it like more white then anything?

the_adam
01-05-2012, 12:42 PM
I do like the bike "borrowing" idea... Trouble is if I did that I'd almost certainly turn up on a streetfighter, and then be sat on the naughty step all day :chuckle:

Guess I could try the plugs, with the initial problem being fuel-related he probably wouldn't have checked them... trouble is it's not really what you'd call intermittant, once I've been on the motorway for long enough (presumably to make whatever is causing it hot enough) I can make it happen whenever I want, simply by slowing down to somewhere around 3000-3500 rpm, depending on the slope. I'd imagine if it was spark related it would happen regardless of how I'm riding, or even be worse when I'm going faster?

There's no smoke as such coming out from the top of the cylinder, just a release of some kind of gas... everything looks normal at the exhaust end too.

The geography teacher that doesn't like it is telling me I need to buy his fireblade again :hissy:

Saint aka ML
01-05-2012, 12:53 PM
I am asking about colour as if it was like thick smoke kind off white in look it would be confirming misfire via airbox. It does look like it. If that is the case then in short one of your cylinders is not always igniting the petrol correctly. It could be because injectors are malfunctioning. It would be heat and rev related. It heats up and wires going to injectors start having higher resistance or not always connecting as rubber housing has stretched. It is happening at low revs as I think there are two injectors per head on 695 low running and top end.

It could also be spark not strong enough so it fires but is not strong enough to properly ignite mixture. If you can make it hiss at will then when it starts, swap sparkplugs and see if hissing moves.

utopia
01-05-2012, 05:24 PM
I've been pondering, but haven't got very far.
I guess the hissing noise can only come from pressure somewhere, and the two sources are 1)cylinders or 2) fuel system.
I know next to nothing about injection systems, but there is a full explaination in a sticky thread "monster tech. fuel system by capo" which may be of interest, and is the main reason for this post.
As for cylinders....loose plug, head gasket leak (broken stud ?), valve leak (damaged valve/seat or clearances out of adjustment), exhaust clamp leak (my 350 yam hissed thus)......???

Failing that, you have a nest of snakes in the airbox and, being cold-blooded, they don't start hissing until they've warmed up a bit ?
Ferret...???