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748SP 1996
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Discussion Starter #1
Hello all!

New to this forum and new to Ducati aswell. I bought mine 748SP a month ago.
I got some really weird problems with my bike and I hope you can help me to find a solution to this so let me start from the beginning.

Everything started with the bike acting bad when driving it, at around 3500-4000 rpm it acts like it was bouncing of the rev limiter for about 2-3 sec even if I was att full throttle
and then it would just pick up and take off like a mad man. This was even worse after the last wash a couple of days ago and then it developed a "sneeze" sometimes when idling and drop in rpm. I don't wash my bike with a pressure washer, just a garden hose but I thought it was probably water getting in somewhere where it shouldn't so I decided to try to find the fault the next day.

Checked spark plugs and leads, checked the famous yellow wires and one of them was a bit melted but not bad at all. I charged the battery to full and hooked it in.
Turn the key and the fuel pump didn't prime at all... Annoyed by this new problem I hooked in 12V directly to the fuel pump and it was running like it should. Checked the 2 relays under the seat and hooked them both up to 12v to test them and they both worked. Checked the leads and couln't find any problems. After some thinking and reading on this forum
where there were mentions of bad eproms. So I casually just tapped the eprom chip and turn the key and the pump primed. Happy that I found the problem I immediately order a new 066 eprom. Since I got the 060 eprom aswell I changed to the original cans and that eprom and it primed as well after that. Bike started like it should and I went in to get my gear. Just as I got back the bike stalled and I heard the fuel pump still running. Tried to start it again but once again the pump didn't prime. Decided to measure pin 23 on the ecu which should power the relay for the fuel pump if I got it right. With ignition on I got 7,5V and more strange when the pump decided to prime I sometimes got 10-11V and even 1V! The engine always run between 30 sec to 1 min and then just stalled. I'm afraid that my ECU is bad but I'm hoping you might have another answer to this?
 

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748SP 1996
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Discussion Starter #2
My non start condition cured itself after a couple days and I have not had any problems with that at all. Tracked it down to probably water somewhere where it shouldn't be becuse I washed the bike thoroughly the day before.

But my problem with the bike acting weird around 3500-4000 rpm still persist. If I floor the throttle in like 3rd gear it acts like it's on the rev limiter but if I back of the throttle a fair bit it manages to come past 4000 rpm and then just starts pulling as usually until I come to 7000 rpm then it pulls really slowly again and after 8000 it picks up again and goes like mad.

Checked connectors to ignition pickup sensor and measured it and it was in spec. I solved my charging issue also so it's not that either. Connected a diagnostic tool but no fault codes were present, tested all that can be tested with the diagnostic tool and everything passed. Played little with the CO-trimmer but no luck there either. When I rev it in neutral it works like a charm. Kinda thinking it might be the EPROM or maybe even the computer in the end?

Does anyone else had this problem or knows what might be the problem? Thinking of sending the computer away and let someone check it out but would really appreciate if anyone else have some inputs regarding my problem.
 

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Do a LOAD TEST on the battery before wasting more time. Bad battery with an ECU can cause bike to go nuts . Happened to me twice last year, different symptoms, same issue. Old Battery that checked 12v + until a load , then crazy shit starts happening. Also clean all your grounds to bare metal. My S4RS ECU was grounded to plastic at the factory. I ran a jumper wire from there to the main battery ground.
You have issues after getting things wet. I would examine the wire closely and repair anything the least bit dicey. Plug and unplug connectors and spray them with wd40 or whatever.
 
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Discussion Starter #4
Do a LOAD TEST on the battery before wasting more time. Bad battery with an ECU can cause bike to go nuts . Happened to me twice last year, different symptoms, same issue. Old Battery that checked 12v + until a load , then crazy shit starts happening. Also clean all your grounds to bare metal. My S4RS ECU was grounded to plastic at the factory. I ran a jumper wire from there to the main battery ground.
You have issues after getting things wet. I would examine the wire closely and repair anything the least bit dicey. Plug and unplug connectors and spray them with wd40 or whatever.
Interesting. I'll do a load test and check all my grounds. I have already checked my connectors and cleaned them all, no one was dodgy from the looks of it.

Poured in some injector cleaner and just came back from a big ride but that didn't make any difference. My problem seems to be electrical.
 

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The symptoms you describe are well known and discussed here on this very forum. Search 996 3500 rpm hesitation. You can substitute “stumble” for hesitation in your search.

Also, read this:

Much of the pertinent information is contained on page 3 though there is some discussion beginning toward the end of page 1.

I tend to agree with the position it is caused by an ignition curve error, as I have a UM191 eprom chip installed and my 996 still has the same stumble/hesitation/burble as described in the speedzilla thread.

The only thing making me scratch my head is, the description there describes what I’m experiencing exactly. Except mine occurs at or around 5K.

I’ve got some diagnostic cables on the way so I can plug in and see what is going on with TPS voltage, and fuel/ignition maps.

If you can’t see that stuff, it’s just a guessing game as to the source of the problem.
 
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the 996 3,500 rpm stumble on acceleration is nothing to do with any other stumble or misfire or whatever else you want to call it. it was a wacky dynamic issue all its own.
 

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Discussion Starter #7
This is not that famous 3500 rpm hesitation. Suspecting that it was something fuel related becuse when I back of the throttle the bike starts to pick up and I can get past which indicates it's running lean. I connected my fuel gauge and sure enough I only got 20 psi fuel pressure.

Next thing is to check the fuel assembly. I suspect either a bad hose or maybe the fuel regulator is stuck open?
 

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the 996 3,500 rpm stumble on acceleration is nothing to do with any other stumble or misfire or whatever else you want to call it. it was a wacky dynamic issue all its own.
Would you care to elaborate any or has this subject been done to death else where? Seriously. I quite curious to read your take on this.
 

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i probably should rewrite and condense these 3 into something more concise and with less speculation or attempted humour, as some just interpret things i write nothing like i meant.

if you don't have a 996, and haven't experienced a hard, roll on misfire at 3,500rpm (and only 3,500rpm) then you really won't understand the issue.

 

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I thank you for sharing that.
The 996 Strada 3,500 RPM misfire is a very unique and wacky thing. On a bike that does it, it is a totally repeatable phenomenon. You cruise along at 3,500 RPM and whack the throttle open. The bike goes duh – duh - duh – duh - duh – duh - duh and then takes off. It’s very specific – they don’t do it at 3,000 RPM or 4,000 RPM or any other RPM.
What I am experiencing is exactly this. Only at 5K rpm or there abouts. It is, exactly as you state; very specific.

I have the UM191 eprom. Essentially the OEM exhaust with Termi slip ons. 2000 996. AFAIK, it has the stock Strada cams and has not been set to your recommended 108 degrees.

It was set up this way when I bought the bike. With the same gearing too. 15/39. At 5K I’m at highway speed 75ish MPH in 6th.

Initially, it feels as though I’ve throttled off, though I’m at a steady throttle. When I roll on the throttle I get the duh-duh da duh duh duh and then bang. Off to the races. It does this in any gear, at around 5K rpm.

In lower gears when it happens the rear will begin to pump in time with the stutter.

Above or below that specific rpm it’s beautiful. Pulls hard enough to set your eyeballs back in your head. If I crank open the throttle from a stop, it’s fine. Trying to accelerate from cruise....nightmare.

I’m no expert. I know one end of a spanner from the other. I’ve ordered some cables so I can connect and see what he’ll is going on. Maybe then I can figure something out. Thank you for your time and the info you posted. If I come up with an answer, solution or whatever, I’ll post here. Emham, I apologize for the thread jack.
 

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Again, thank you. I did not know that. I've considered other eproms just to see if the one I have has a fault.

A forum member here is selling a FBF eprom and I've previously thought that might be stab in the dark solution. If the one I have can't be accessed via a diagnostic program then a new eprom it will have to be.

I've got no illusions though. I really just want to see what is going on with TPS voltage, fuel and ignition map information.

Mainly because this 996 has run rich since the day I brought it home (you did address that in the articles you wrote) but it really is problematic.

To the point it is fuel fouling the plugs. Might be the cause of the stutter/stumble/hesitation or whatever we want to call it. I don't know, and won't until I can see what is going on at that throttle position. I hate guessing.
 

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Discussion Starter #13
I thank you for sharing that.

What I am experiencing is exactly this. Only at 5K rpm or there abouts. It is, exactly as you state; very specific.

I have the UM191 eprom. Essentially the OEM exhaust with Termi slip ons. 2000 996. AFAIK, it has the stock Strada cams and has not been set to your recommended 108 degrees.

It was set up this way when I bought the bike. With the same gearing too. 15/39. At 5K I’m at highway speed 75ish MPH in 6th.

Initially, it feels as though I’ve throttled off, though I’m at a steady throttle. When I roll on the throttle I get the duh-duh da duh duh duh and then bang. Off to the races. It does this in any gear, at around 5K rpm.

In lower gears when it happens the rear will begin to pump in time with the stutter.

Above or below that specific rpm it’s beautiful. Pulls hard enough to set your eyeballs back in your head. If I crank open the throttle from a stop, it’s fine. Trying to accelerate from cruise....nightmare.

I’m no expert. I know one end of a spanner from the other. I’ve ordered some cables so I can connect and see what he’ll is going on. Maybe then I can figure something out. Thank you for your time and the info you posted. If I come up with an answer, solution or whatever, I’ll post here. Emham, I apologize for the thread jack.
No worries, we seem to almost share the same problem only that on my bike it occurs on 4K rpm and exaclty the same thing as you described. My bike hits another "wall" at 7K RPM and over on higher gears like 5th and 6th where it pulls painfully slow and almost stops accelerating which got me to measure my fuel pressure. Does your bike maybe act the same?
 

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No. The issue I have is right around 5K. It starts a bit before, maybe 300 rpm and lasts to around 5300-5500 rpm.

It pulls clean and strong otherwise, at or from any other RPM. It launches clean through that spot so long as I’m well into the throttle when I get there.

If I’m at highway cruise or accelerating from cruise I get the duh dud da duh duh duh until the revs pick up past the 5K range. After that, pull to redline is strong.

This is why I suspect it is TPS related. May not be just that, but I think that it plays a part.

Otherwise I see no real reason for the issue to be stuffed in that narrow space on the tach.

I suspect the eprom I have could have a fault of some sort that combined with some glitch from the TPS at that throttle position exacerbates it.

Also, I’ll need a different eprom as @belter already established that the UM191 isn’t going to “talk” to any diagnostic software.

Your higher RPM issue is confusing to me. Might be fuel pressure or volume related. Also could be air flow related.
I don’t know though as I don’t have your bike in front of me to eyeball and test.

I’ve not ridden a 748 in a long time. I rode a pretty well sorted S probably 15 years ago. It felt similar in many ways to my 996 but without the stumble and the outright power at lower RPMs.

Cables are supposed to be here soon so once I learn my way around the software suite I’ll get to troubleshooting.
 

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Discussion Starter #15
I understand. To me it sounds like you are on the right track finding the cause of your problem. Will be interesting if you find something with the diagnostic software.

I'm pretty positive that my problem is becuse of the low fuel pressure since it's half of what it should be, just need to find some time to check why it's that low. Interesting to hear your experience with a 748S since this is my first Ducati and I've had this problem since I bought the bike 3 months ago so can't campare to anything.
 

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Discussion Starter #16
Finally had some time today to remove the tank and check out the fuel assembly. Found the problem straight away, a split line from fuel pump to filter. Parts ordered and looking forward to try the bike out after that. Thank you all for the help!

990103
 

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I had a similar issue on my 748. Took it to many shops and none could figure it out. Then one day I just started taking the bike apart to find the issue. I found that most of the connections on the main wire harness were corroded. I got stuck in the rain a few years back and everything got soaked. Once I cleaned up the corrosion and put electric grease on the fittings the bike ran perfect every time.
 
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