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Discussion Starter · #1 ·
Well after only 1500 kms on my new st3 she is giving trouble. In neutral she revs quick and hard no problems. Put it in gear and take off it breaks down underbload.
Replaced plugs
Replaced fuel filter and fuel pump
Checked electrical plugs
Checked belts and timing
Still doing it.... any other suggestions as Im now out of ideas.
All comments appreciated

Cheers
 

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Does sound like spark, could be a coil or plug leads. Possible it is corrosion in the lead at plug or coil ends. Taking plug lead off and crank over it should be able to through a spark over 1/2" long. Plug leads should be less than 13k ohms, around 6-7k is good.
 

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Please make a signature file with your bike in it. Give the year and precise model (ST3 vs ST3s vs ST3s ABS), so that we don't have to always ask.

Even though you replaced the FI pump and filter, did you replace the whetted lines? They factory lines are notorious for failing. Mainly on older machines, but not unheard of on the ST3 machines. When my 1998 ST2 "failed", it would idle, and rev slightly above idle, but no normal throttle.

One way to diagnose is with your ears. Open the lid. place key into ignition and turn the key on. When the pump cycles for 2 seconds, you can hear/see bubbling or gurgling. If you see/hear a WHOOSH and a lot of activity in there, your line is bad. You need to do it in a quiet place, because I could not tell any difference outside, until I got home into my garage.

BTW, I was able to limp my bike home about 40 miles with a 1" slit in one of the lines...

Also, if you dig in there again, be SURE to buy FI line rated for submersion. Not cheap. Maybe $30 or $40 a foot from our local auto parts stores.
 
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Just to clarify does it move under its own power or die before moving?
Have you tried to clutch out in gear on the center stand with the rear wheel off the ground?

Verify there is not some drag in the drivetrain.
Plugs out can you turn the motor over in gear with the rear wheel off the ground?

Just make sure it is not a clutch/gearbox or drive issue. Since it works fine in Neutral there may be something else causing the issue.
 

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Discussion Starter · #6 ·
Thanks for your comments, all fuel lines tested and good.
As far as drive lines go it all seems fine. I can ride the bike if i dont “wrap” it on......

Its starting to get frustrating!!

Appreciate anymore idea
Cheers
 

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You do mention it is new, did it ever run right for you?

Did you do a compression /leakdown test ever?
you checked lines did you test fuel pressure?
Have you checked the airfilter for obstructions?

I can ride the bike if i dont “wrap” it on......
Sorry but I am not clear on what you mean.
If you slowly roll the throttle open and do not go past say 1/4 throttle will it accelerate through the gears?
If you can get to 1/2 throttle is it normal?
If you get to full throttle is it normal?

Before you try these tests make sure the motor spins easily with plugs out and by hand, as we do not want to do more damage if something bad happened.
Check for fuel,spark and compression then expand the hunt for something out of spec as in the timing or strength of the compression,spark or fuel. Rule out the bad things first and work into the harder to find but other important settings. Does it have a power commander or anything non-oem?
 

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I have had twin spark motors before where a single faulty plug or lead caused a misfire. Some motors like the Nissan ca series the second plug cuts in at higher rpm so the miss will occur either at idle or only above a certain rev.
In the case of the Ducati, I believe the twin spark is to reliably ignite leaner mixtures and of course to promote more complete combustion.
 

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I have had twin spark motors before where a single faulty plug or lead caused a misfire. Some motors like the Nissan ca series the second plug cuts in at higher rpm so the miss will occur either at idle or only above a certain rev.
So how would it be affected if the two on one side were reversed?
 

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Should also note, the amount of spark energy needed to ignite the mixture varies with combustion pressure which is largely determined by throttle. In other words it takes more spark to ignite if your twisting it on.
 

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Also note that you could have a lean misfire, this is when the mixture goes so lean that the ignition system can't ignite the fuel despite working normally. Lean mixtures are hard to ignite and the mixture is often not the same throughout the cylinder with some areas being richer or leaner. Manufacturers try to place plugs where the mixture is likely to be richest.
 

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Discussion Starter · #13 ·
Wow, thanks for all the comments!
I will try and cover a few questions.... I am in Perth WA, the bike has 20,000kms on it and mechanicaly it has been checked and fine.
Fuel pressure ok
We are currently locking at coils.
It runs sweet without liad and revs instantly to the moon.
Put it under load and thats when the trouble starts.
Slowly rev the engine through excleration and again all good. As soon as you ask for gas it crumbles.
I am considering blocked injector? How can you test them?
Is it fair to say ecu is ok?
Regards
 

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I asked your locality because we have a pretty good bloke here at Byron Bay over east. It's called Desmo Headquarters.
Sorry I don't know a lot about these bikes but it sounds like the spark is breaking down under load, hence you checking the coils, but isn't there an ignition module before the coils that could be failing? Not sure. I had an ignition module fail on a car that did similar stuff.

You've checked all connectors such as to the TDC sensor but how did you check them? Take them apart, clean and coat with a dab of vaselline? Wire brush them or squirt with electrical cleaner? No doubt someone will be here soon to explain the correct method. But sometimes there's invisible corrosion on those contacts that has to be polished off somehow for full functionality.
Also no doubt you've checked the battery and the amount of charge going into it. After these things I would probably take it to the shop unless I could find expert advice such as I hope will follow this layman's first attempts.
All the best, I'll be watching and learning with you.
 

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We are currently locking at coils.
Something to check for sure But the stock coils are good enough I have only changed a handful out of need in over 20 years now so unlikely.

Fuel pressure ok
That's too bad as it fits the symptoms of a failed/failing fuel line or plugged fuel filter. Not all lost though as this may point in a direction to go.

It runs sweet without liad and revs instantly to the moon.
Going to assume you mean load not liad though I always run sweet too after getting laid. :grin2:
I assume this only applies to running in Neutral.

Put it under load and thats when the trouble starts.
Slowly rev the engine through excleration and again all good. As soon as you ask for gas it crumbles.
So the question is it a problem with not enough fuel at higher throttle settings? I just mapped a bike on the dyno that would not pull past 3000rpms when held at 10% throttle in third gear. This was due to the bike being too lean and when I added fuel to the map at that rpm and throttle angle it suddenly would pull past 3000 to the next lean spot. This is why it would be best to do a more air /less air test on it to see if you can tell if you are simply running too lean. Then you can figure out the next 2 questions of why and what to do about it.

I never heard what condition the airbox is in.
fully stock with no extra holes and snorkles?
no snorkles?
cut or drilled extra holes?
no airbox - pod filters?

Fuel pressure being fine means no leaks or obstructions so it is a matter of the bike having something like a tps sensor failure giving bad information to the computer. A incorrectly set TPS , a bad ecu. I would check the crank angle sensor though the fact it runs good with no load points away from this it still should be checked. Injectors can be cleaned BUT it is VERY rare to have a bad one in my experience so though possible it is unlikely. Most will not function at low throttle any better than full throttle when bad so possible but unlikely.

I would do a more air/ less air test and see if you get some direction.
Close up the airbox so there is only one snorkle hole open and see if it is better or worse, not fixed just better or worse.
Then try the same test with NO airbox lid, zip-tie the air filter in place so NOTHING can get past the air filter and blow up your motor.

Being a ST3 you have an ecu that is fragile if you run power down a ground line, if the ground has been damaged in the ecu then the bike will run in limp home mode and be very rich. This could cause the problem but a experienced ducati mechanic should hear the difference even at idle. If you jump the diag. port ground wire to ground and it suddenly runs right your ecu ground has been blown. Often this will foul plugs so look and see if the plugs are dark before heading down this path. Also know if you do the test wrong you risk damaging the ecu so pay attention. There is little room for error with these ecu's, they are reliable overall but if wiring has been tampered with it is possible to fry one.

If in Doubt get the bike somewhere that air/fuel can be tested and it will point you in the direction of what it wrong. Yes this will cost you some money but probably no more than throwing parts at it that it does not need.
 

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I had a simliar issue with my multistrada last year. I experenced the same symptoms and the culprit was water in the gas tank. The water came from an ill-fitting aftermarket gas cap.
 

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I have experienced water in fuel a number of times on different bikes, usually it causes bad running everywhere not just under load
I would check the ignition system first to eliminate, it's easy after all. Plug leads are tested with multimeter set to ohms disconnected at both ends. Spark plugs can be easily tested and coil is load tested by seeing how big a gap it will jump.
If ignition checks, probably worth checking TPS, once again easy to test with multimeter, procedure is in manual I think. Just measure resistance while slowly a accelerate looking for nice smooth change.
 

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Discussion Starter · #18 ·
Well, a few hours of pain and none the wiser!
Things done
New fuel pump
New air filter
New tps
Reset tps to 2.3 degrees on diag
All electrical plugs double checked
New plugs
New coils
Ht leads checked and ok
Cleaned fuel tank out
Cleaned injectors
Mechanicaly all good
Put a earth wire from dig cable to earth


I really appreciate all your comments and advice as I am now at a loss

Maybe a fried ecu?

Does anyone have one for me to try as thats all thats left im thinking

Thank you guys
 

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Surely there's a pro Duke shop there that can diagnose it for you mate. Really you've gone past the point of throwing stuff at it without knowing wot the F is going on? For the price you will pay it will save you in the end. Dare I say this should have been your first call?

I know how it goes when you get desperate. I did it with a Volvo once and ended up selling it for scrap because I refused to get proper help. And I've seen a few on this forum go down the same path.

The bike is probably quite good but without the magic ingredient you won't be the one to enjoy it. Someone else will clean up on your frustration. So Please find a good shop and let them play with it. That's if there is such a shop over there.
That's the question you need to be asking right now IMHO.
 
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