[RI749]

Could be a lot of things. Where does your friend live?

 

[bubbazenetty]

Have him check the TPS setting.

 

[blade625CT]

Hey guys this is my old bike. Let's help this guy out.

This cutting out problem is new to the bike [bike never did it while I had it]

I set the TPS, and hit 150mv dead nuts [of course it could be off 2-3 few mv due to accuracy of the meter] So I wouldn't think that's it. But that is far better than the 14mv it was off when I checked it originally...and it ran then.

I had, however, set my idle AFR to about 13.7:1 [using a lambda meter w/bosch sensor...and the CO trimmer in the ECU] the last time I was out riding/tinkering with it. I set it to that on the advice of another racer, and it really made a nice difference. BUT, I set it while the bike was good and hot and never had the opportunity to start it again from cold until the day Todd picked it up [and it was a bit difficult to start] it was also a damp raining day when they came to get it...and I had never started the bike in the rain either....

Do you guys think electrical? or fueling?

The only time the bike ever failed to start and run for me was when a dry break [quick disconnect] failed at the track. It failed in an unusual way, in that it quit passing fuel...so I had low fuel pressure and the injectors wouldn't fire.

I finally, after much testing, discovered the problem and replaced the QD. So unless that happened again [doubtful] that shouldn't be it.

It has a fresh fuel filter, so that shouldn't be it either.

 

[SeanFromTX]

Rainman was lookin' out for me and told me about this thread. Sounds like the same problem I'm having and aint figured out yet. With that said, I'll describe the symptoms I'm having so we can collaberate on a resolution. I have a 1999 748 with ~16K miles. The only engine mods I have that could contribute to the diagnosis are; Termi slip-ons, JHP air filter and a FIM chip. I have CF intakes so the inline air filters no longer exist.

1) I'll take the bike out for a ride. The symptoms do NOT happen immediately.

2) It seems to take at least 20-30 minutes before it occurs(this is a guestimate).

3) When I approach a stop sign/light and pull the clutch in, the motor goes to idle, but dies within a few seconds. During those few seconds it's very erratic. I can blip the throttle to keep it running until I need to go, but it's a pain in the @$$. If I wanted a TZ250, I would have bought one.

4) I've also experienced another unwanted behavior that I believe is related to the stalling while stopping problem.

5) While riding down the highway, my 748 will start to surge/stumble around 5-5500 rpm. When this occurs, I can pull the clutch all the way in and the bike will stall. I let the clutch out which immediately "bump" starts the engine. When it occurs I can get on the gas and ride around 6-6500 rpm and the bike will recover from the condition. It can get pretty annoying.

- Because the issue was intermittent, I went with replacing the fuel filter first. I also replaced the spark plugs and cleaned the air filter. I went ahead and replaced the high pressure hoses as preventative maintenance because I had given a guy an 85 mile ride because his had split. My fuel sending unit broke around the collar so I had to replace that because the fuel would leak. I had both the 6 and 12K services performed by my local Ducati shop and it's always ran fine when I've picked it up.

I hope the extra information aids some of you knowledgeable folks in determining what the problem is. I haven't posted up because I have an absolutely bullet proof ZRX1200R that never let's me down. I really cannot afford to hand it over to the shop for stuff like this. I do bite the bullet at the maintenance intervals as I believe I'm getting some value out of that.

Thanks Mr. Bill !!!

My fingers are crossed,

 

[blairjw]

Thanks both Seans'

From what I have found problems associated with the TPS manifest themselfs as stalling at traffic lights.

Found some other threads about a white connector behind the battery that seems to have some issues.

We will check it out this weekend...


Blair

 

[blade625CT]

just want to keep this up top where someone might think of a possible cause/solution.

Blair, let me know how you and Todd make out this weekend, and whether you need a fuel pressure testing rig [i'll lend you mine]

It will allow you to check pressure, and run the bike with the tank off on a side stand. It hooks directly into the QD's between the tank and the TB's

Btw..i'm pretty sure i dielectric greased the connector you are refering to...but can't remember for sure.

 

[level7]

If you have a sidestand bypass, jiggle that bad boy while in neutral and the engine running.

Early on, I had very rare stalling problem coming up to lights, maybe once or twice. I couldn't tie it to anything but now I know it was probably the side stand bypass someone put on my bike before I bougth it.

It recently got worse, no rhyme or reason, stall/cutout. Then normal operation. Seemed it was fuel related but wasn't. Luckily, my installation of my bar risers brought it to light. All it took was a slight (and I mean slight) tug on the sidestand bypass and voila! stalling/sputtering/dying.

Anywhere someone installed those crimp jumpers or T-taps, double check those. They WILL go bad after a few years especially with the heat these motors put out. This recently happened to my Jeep. I had a alarm put in when I first bought it. Five years later, I had lighting issues. It was the T-taps, some of them worked themselves loose.

 

[Matt748]

Just bought a 98 748/853, runs like a clock, but now I'm having problems starting it. It either starts or it doesn't, no stalling yet but I only have about an hour and a half on it on 3 or 4 different occasions.
Now I'm familiar with car mechanicals but I know absolutely nothing about bikes, do you guys have any ideas? I took the tank off and wired the fuel pump to a battery and it runs (pump), drained the gas...doesn't look like there's any water...what gives? To be honest I've experienced bad gas before...twice...and this is way too hit or miss IMO.

I searched the archives and heard level7 talking about a side-stand bypass? What is that and how do I know if I have one to check??

Now with the tank off and everything it doesn't seem to have spark, any ideas??

Sorry to bring only ignorance to the table here, thanks for the time, appreciate ANY advice.


Matt

 

[blade625CT]

No side stand bypass on '98 bikes. So forget about that.

How are you checking for spark?

 

[Fariborz]

Just bought a 98 748/853, runs like a clock, but now I'm having problems starting it. It either starts or it doesn't, no stalling yet but I only have about an hour and a half on it on 3 or 4 different occasions.
Now I'm familiar with car mechanicals but I know absolutely nothing about bikes, do you guys have any ideas? I took the tank off and wired the fuel pump to a battery and it runs (pump), drained the gas...doesn't look like there's any water...what gives? To be honest I've experienced bad gas before...twice...and this is way too hit or miss IMO.

I searched the archives and heard level7 talking about a side-stand bypass? What is that and how do I know if I have one to check??

Now with the tank off and everything it doesn't seem to have spark, any ideas??

Sorry to bring only ignorance to the table here, thanks for the time, appreciate ANY advice.


Matt

Matt,

More than likely your ignition relay,emergency ON/OFF relay or EFI relay has gone bad or is intermittent.

Typically speaking a voltage difference between pin 85 and 86 on a relay will cause the relay to open or close (depending on the type of the relay). That means that when the relay is energized there will be contact between pin 87 and 30. If your relay has a pin 87a, when the relay is not energized pin 30 will be connected to pin 87a.

A good relay should have very little resistance between pin 30 and 87 when energized. If your relay has a quenching diode inside to prevent a voltage spike when voltage differential is removed from pins 86 and 85 the polarity of the wires to pins 86 and 85 is important. The striped end of the diode should be connected to the positive terminal. On the housing of most relays there is a drawing showing where the ends of diode are connected to. The diode is designated by a rectangle with a vertical line on one of its vertices parallel to the opposite side. Positive voltage should be applied to the terminal that is connected to that end of the diode with the vertical line (cathode). If the polarity is reversed, then the diode will be shorted and damaged. If your relay ONLY has a resistor then you can connect pins 85 and 86 to a differential 12 volt without having to worry about polarity.

To check a relay, removed it from its housing. On the bench, connect pins 86 and 85 correctly to the battery (check polarity in case there is a diode in your relay) then measure the resistance with a voltmeter between pin 30 and 87. As you connect and disconnect the battery connection to terminals 85 or 86 watch the resistance between pins 30 and 87. You should be getting a REPEATABLE resistance of approximately 0.1 ohms. If you are getting above 1 ohms or the resistance fluctuates, you have a bad relay.

If you need more info on relays, go to the following web site and on the menu on the right go down to item 36 that is relay. Click on the relay link and you can then read all that you need to know about how a relay works.

http://www.bcae1.com/

I had a similar problem to yours but to make the matters worse it was intermittent. It took me a while to figure out what was going on, because my problem was not repeatable. In my case the coil/fuel pump relay had a resistance of about 70-80 ohms (occasionally). In some cases, I could hear the fuel pump energize but the coils were not firing. When I was hitting the starter, the engine was turning and turning but with no spark. For the heck of it I opened the relay and looked at the contacts. I had arcing between the contacts. Just picture in your mind trying to align two cones with the sharp tips against each other. Some times only the points were contacting each other and some times the sides of the cones. I sanded down the contacts and the resistance went down to around 0.1 ohms. For the peace of mind I replaced the relay anyway. While you are at it, I think it will be a good idea to check all of your relays this way you know for SURE they are fine. You can then eliminate them from your list of suspects.

If you have a bad relay, I do recommend you replace all of your relays. They are of the same age and have similar number of hours of usage. I had a second relay go bad within two months after the first relay went bad.

Also note that in some cases a bad battery or dirty/corroded battery terminals can manifest themselves with similar symptoms.

-Fariborz

 

[Matt748]

Wow, that is some amazing information...I am really impressed. I should be able to get on that tomorrow, that sounds like exactly what's going on!

I got the fuel pump and spark back tonight, but didn't put the bike back together. I was dead on my feat and had to finish my homework. BTW I was checking the spark with a spare plug holding it against the head. I didn't hear the pump priming inside the tank, but it's doing it now when the key comes on...it wasn't before, and on cranking it seems I got both the spark and the priming pump back at the same time (pump just hooked up to the bike outside the tank).
It seemed like all this could have corresponded to me fiddling with the kill switch but honestly that could be complete coincidence I have no way of telling after one night.

Anyway, thanks a TON guys I really appreciate it. You'll hear from me when I have something to tell.


Matt

 

[Fariborz]

I didn't hear the pump priming inside the tank, but it's doing it now when the key comes on...it wasn't before, and on cranking it seems I got both the spark and the priming pump back at the same time (pump just hooked up to the bike outside the tank).
It seemed like all this could have corresponded to me fiddling with the kill switch but honestly that could be complete coincidence I have no way of telling after one night.

Matt

Matt,

The contacts in your ighition switch might ALSO be dirty. I recommend you use an electrical contact cleaner to clean the contacts in your ignition switch. But I am 90% sure, you have intermittent relay problem.

-Fariborz

 

[blade625CT]

Matt,

More than likely your ignition relay,emergency ON/OFF relay or EFI relay has gone bad or is intermittent.

Typically speaking a voltage difference between pin 85 and 86 on a relay will cause the relay to open or close (depending on the type of the relay). That means that when the relay is energized there will be contact between pin 87 and 30. If your relay has a pin 87a, when the relay is not energized pin 30 will be connected to pin 87a.

A good relay should have very little resistance between pin 30 and 87 when energized. If your relay has a quenching diode inside to prevent a voltage spike when voltage differential is removed from pins 86 and 85 the polarity of the wires to pins 86 and 85 is important. The striped end of the diode should be connected to the positive terminal. On the housing of most relays there is a drawing showing where the ends of diode are connected to. The diode is designated by a rectangle with a vertical line on one of its vertices parallel to the opposite side. Positive voltage should be applied to the terminal that is connected to that end of the diode with the vertical line (cathode). If the polarity is reversed, then the diode will be shorted and damaged. If your relay ONLY has a resistor then you can connect pins 85 and 86 to a differential 12 volt without having to worry about polarity.

To check a relay, removed it from its housing. On the bench, connect pins 86 and 85 correctly to the battery (check polarity in case there is a diode in your relay) then measure the resistance with a voltmeter between pin 30 and 87. As you connect and disconnect the battery connection to terminals 85 or 86 watch the resistance between pins 30 and 87. You should be getting a REPEATABLE resistance of approximately 0.1 ohms. If you are getting above 1 ohms or the resistance fluctuates, you have a bad relay.

If you need more info on relays, go to the following web site and on the menu on the right go down to item 36 that is relay. Click on the relay link and you can then read all that you need to know about how a relay works.

http://www.bcae1.com/

I had a similar problem to yours but to make the matters worse it was intermittent. It took me a while to figure out what was going on, because my problem was not repeatable. In my case the coil/fuel pump relay had a resistance of about 70-80 ohms (occasionally). In some cases, I could hear the fuel pump energize but the coils were not firing. When I was hitting the starter, the engine was turning and turning but with no spark. For the heck of it I opened the relay and looked at the contacts. I had arcing between the contacts. Just picture in your mind trying to align two cones with the sharp tips against each other. Some times only the points were contacting each other and some times the sides of the cones. I sanded down the contacts and the resistance went down to around 0.1 ohms. For the peace of mind I replaced the relay anyway. While you are at it, I think it will be a good idea to check all of your relays this way you know for SURE they are fine. You can then eliminate them from your list of suspects.

If you have a bad relay, I do recommend you replace all of your relays. They are of the same age and have similar number of hours of usage. I had a second relay go bad within two months after the first relay went bad.

Also note that in some cases a bad battery or dirty/corroded battery terminals can manifest themselves with similar symptoms.

-Fariborz

An admin. should take this post and put it permanently into the "hall of wisdom"

This is some good info to keep around.

nice post Fairborz!

 

[Matt748]

Well I can't thank you guys enough..

Checked all the relays (3) according to what's described above and they all checked out. I'd like to explain a little in detail because I know there will be some guys on here, like me, that are a little intimidated when someone starts talking about tab 30 and tab 87, etc. All you have to do is take the relay box off and the tabs are labeled for you, couldn't be more clear. From there you just crimp a connecter onto the end of a speaker wire and put it over the prescribed tabs, hook it up to a spare car battery on a bench, and check your continuity (terminology?) across; couldn't be easier. If you want to see it in a book I happened to find it flipping through the hardcover Hanes manual described on page 9.17, under headings 22 and 23.

Well I'm not sure what fixed it. To be honest we (my dad and I) had the fuel pump priming and spark back, inexplicably, before we did this test so there may be a gremlin yet in the machine but for now the bike is running flawlessly and we know where to look. I also cleaned up the battery terminals just because everyone hears weird stories and I don't want to start any. My advice for anyone experiencing this would be listen for the fuel pump priming and follow the same line of inquiry.

Hope someone gets something out of all this, I know I did a lot of learning today and feel a lot more comfortable around and on the bike having had my hands into it. Weird how that works.

Thanks Again


Matt :abduct:

 

[Fariborz]

... Well I'm not sure what fixed it...
Matt :abduct:

Matt,

Don't you hate that! It is like you want to trust your bike but deep down you don't know if you can! When I was having intermittent relay problem, the bike would die suddenly while I was riding. Nine out of ten, it would start up again but that one time it would not. I knew it was an electrical problem (most mechanical problems do not get resolved automagically). I suspected it was a relay issue but when I wanted to test it, the bike would not misbehave. Until finally one day the situation reversed itself and nine out of ten times, the bike would not start. It was then when I was able to find the problem. I first started by swapping relays to find the bad relay and after that I started doing whole bunch of tests on good relays and the bad one to be able to find out how to diagnose a bad relay.

BTW, when I started testing my bad relay, few times the resistance was fine and then I was reading some high resistance (intermittent). Next time when you are testing your relays, connect and disconnect the power source 10 to 20 times to see if you get a repeatable resistance.

My recommendation to you is to carry one spare relay and few spare fuses on the bike while you ride. If for some reason the problem happens far from home, you have some spares to work with.

I am glad you are up and running. Keep the rubbers on the road.

BTW, in my previous post regarding the Quenching Diode the schematic designation of a diode is a TRIANGLE with a line drawn parallel to one of its sides from the opposite vertices and NOT a rectangle as I wrote in the post.

-Fariborz

 

[SeanFromTX]

I had my local Ducati dealer hook-up the Mathesis device to my 748 and there were lots of stored codes with some of them being downright depressing to read. Like the ones indicating that the "ECU was bad" or "wiring was at fault". Not what I want to hear for possible problems on my Italian mistress. The Tech told me that this crap was a little tricky to troubleshoot plus he was having a hard time "clearing" the codes to continue on. He managed to get them cleared and retested. If I recall, one of the codes indicated a faulty fuel pump relay as well as the TPS out of spec.

Replacing the relay would cost no more than $13, but I thought a relay failure would manifest itself as either off or on even if it was intermittent. The TPS read 1.2-degrees and 286mv. Keep in mind that this was just plugging in the Mathesis tester with the bike not running and the throttle in the closed position. Rolling the throttle on showed a pretty linear delta in readings with no major spikes. With that said, I read the following from LT Snyder's "Ducati Desmoquattro Maintenance and Modification Guide":

Once the baseline of 150 is acheived, tighten down the TPS screws and readjust the throttle stop screws until 520-560mv is displayed (420-460 millivolts on 1.6 computer). What this does is calibrate the throttle position sensor to read 3-degrees throttle postion for idle, and for all changes to the fuel mixture from idle up through the rest of the throttle openings.

If I'm reading this correctly, the reading I should have seen on the Mathesis should have been 3-degrees and 420-460mv instead of the 1.2-degrees and 286mv. Would you guys agree with that? If so, it may be a simple matter of adjusting the throttle stop screws to acheive the desired result. I guess it would be better to re-basline the TPS at 150mv and then adjust the throttle stop screws. I really don't want to adjust everything mostly because my 18k service interval is 2K miles away and the dealer can perform all those adjustments then.

Forgive me for being gun-shy and thanks Fariborz for that link to all that information. All feedback is appreciated.

 

[Matt748]

Fariborz

Yeah that kills me man. I'm just pretending like nothing ever happened at this point to achieve peace of mind. I've also started doing some yoga.

Yeah we tested the relays several times, we weren't counting but it was at least 20 times per relay. Keep in mind I don't have a fancy guage, it was just showing consistent continuity.

Good advice on the fuses and relay, is there anywhere to pick up relays not at a Ducati shop? I don't have one locally. I think someone said they're only $13?!? Shoot at that price I'll replace them just for the heck of it; again though, is there another place I can get them?

I'm interested in the TPS issue, could that be what's going on for me? I'll check the archives again, but I think last time I tried TPS it told me there were too many threads.


Matt :abduct:
PS Is there a way to check codes by cycling the key on and off?

 

[SeanFromTX]

Good advice on the fuses and relay, is there anywhere to pick up relays not at a Ducati shop? I don't have one locally. I think someone said they're only $13?!? Shoot at that price I'll replace them just for the heck of it; again though, is there another place I can get them?

From the Archives thread below:

http://www.ducati.ms/ubbthreads/showflat.php?Cat=&Board=superbikes&Number=126427&page=&view=&sb=&o=&vc=1
​

I'll share my intermittent starting problem experience. I posted this back on the Ducati Index last July.

I had similar behavior on my 99 748, cutting out going down the road and just after starting up in the AM. The problem was intermittent at first, but it finally failed for good. When I turned on the ignition, the fuel pump wouldn't "prime". There are two identical Engine Management relays(black cubes) under the seat so I swapped them and turned on the ignition. BINGO!. These are pretty standard relays so a trip to my local Autozone fixed the problem for $12.89(GP SORENSEN part #221859 MR125 Relay). I think I saved ~$5-8 over the Bosch unit sold through Ducati that wasn't in stock. However, I probably saved three weeks of valuable riding time waiting for the part.

​

Later,

 

[Matt748]

You seriously rock. I can't thank you guys enough. I can't believe with how expensive everything on these freakin things is that they would use a standard parts store relay, they can't come up with some $500 one to use?! Thank goodness.


Matt out! :abduct: