[Cass]

I've been plagued with an intermittent problem lately and it bit me good today. I was on my '99 M944 several times today and on the last errand I felt it stumbling while I was at a constant highway speed. It got bad enough that it finally just died on me. I thought the fuel tank breather may have gotten kinked so I opened up the tank and tried restarting. It took a bit of coaxing but it fired up. When I revved it up in neutral it sounded like it was only firing on one cylinder. After a couple attempts to take off and the bike stalling, I was able to get it going and get home at lower speeds but it didn't feel quite right. The plugs look like they are in good shape - not sooty.
I rode it the other night without any problems but, this problem has occured in the past but, not to this extent.
Just an hour before this incident I ran it pretty hard (but not at a constant speed) and it didn't skip a beat. It then sat for about an hour and I took it back out and felt some slight surging/stumbling at steady state speed.
Another symptom is occasionally when I pull to a stop, the revs hang at about 2k. That part doesn't sound electrical though.
Could this be an electrical problem? How long do the stock plug wires and coils last?
I'm not sure if I explained the problem well enough but any insight would be helpful.

 

[Guest]

maybe one of your coils is on it's last leg? since they're under the tank, just above the cylinders... when you stopped after your hard riding, the cylinders were cooling off, but their heat was radiating upward and possibly compounded the effects on the coil.

 

[Mark1305]

It may be the dying fuel pump syndrome that I've been crusading against lately. If your bike is carbed and the ignition checks out, get a pump rebuild kit from mfgsupply.com for about $12 including shipping. Takes about 30 minutes to overhaul the pump and have it back in. It's a really cheap way to eliminate one possible culprit, especially since it initially acted like a kinked fuel hose.

As I've posted on many occasions, I firmly believe all the carbed models from the 90s are old enough that the fuel pumps are struggling/dying due to stretched and hardened diaphrams.

Let me know if you need mfg's part #. If you want more details, just search for fuel pump on the board or PM me and I'll overload you with details.

Good luck.

 

[dj]

Heya Mark,

I've been thinking of rebuilding my fuel pump as preventative mainetenance this winter. Could you post that park number? ;D

Thanks!

-dj

 

[Mark1305]

Yep:

Manufacturer's Supply
P.O. Box 167
Dorchester, WI 54425

1-800-826-8563

Part # 451457 "Fuel Pump Kit"

The kit is aftermarket by Winderosa and looks to be higher quality than the pieces that came out of my pump. The Mikuni pentagon style pump is also used in Polaris and Arctic Cat sleds. Just study how all the pieces are in the pump as you disassemble it. Then match up the new parts in the positions they will go. The old diaphrams will probably be two different materials and the new ones will look identical to each other. Watch how the gaskets stack, because the diaphrams have to seat on the correct side of their respective halves of the pump.

 

[Cass]

Thanks for the input. I think I'll try the fuel pump rebuild first. It's cheaper and sounds like worthwhile maintenance if it isn't the problem. If that doesn't get it, I'll throw a dyna coil at it!
Would the dying fuel pump syndrom be intermittent or is it a go/no go problem?

 

[Mark1305]

Cass,

In my case it started to vapor lock and just shut off with that running out of gas sound - which on my bike sounds like one cylinder quitting and then the other as the float bowls empty. I was just arriving at south Daytona (first ride up to Bike Week) I spent the rest of the day nursing it back home and the vapor lock was an on & off thing.

The other quirks that were cured with the pump rebuild were kind of intermittent, too. Like low speed bucking and surging worse sometimes than others. Infrequent backfires under hard acceleration like it was leaning out then back to normal.
The oddest thing was that my plugs were always carbon fouled from around town riding - I blame inconsistent fuel pressure adversely affecting metering consistency in the carbs. High-end carbs like Webers and other mfg's CVs like our Mikunis are sensitive to delivery pressure. All that went away completely with the pump rebuild.

And that's pretty much why I've turned into "Fuel Pump Crusader".

One last tip if you throw in the rebuild kit - When you go to put the new flapper valve discs in, put a tiny dab of silicone grease or something on the little rubber nub that pops into the little tiny hole. You'll see why if you try push them in dry

Good luck with it and give us a report on the outcome, good or bad.

 

[javadave75]

MFGSupply has a new shipment of fuel pump rebuild kits in stock. I have had same problem mentioned on this post and recently bought a rebuild kit to fix the pump. I will have the part here in the next few days and will let you know how things turn out.

 

[dj]

Got it. Thanks Mark!

 

[javadave75]

My karma is kicking me in the ass! My 98 M750 had all the symptoms of a bad fuel pump. Idle is fine but she cannot accelerate or else she sputters and dies. With that and the fact the spark plugs are white showing a lean mix lead me to rebuild my fuel pump. So I put the rebuilt fuel pump on and took her out today and I can't make it over 20mph or else the same thing happens...backfire and dies. One thing I did notice is that I am low on fuel and the low fuel light no longer works and after the bike warms up. There is not a shop here in Louisiana that works on Ducati so I am desperate to find a fix.

Thanks!

David

 

[Mark1305]

Sorry the fuel pump didn't cure it. At least you can cross it off the suspect list. Double check the vacuum hose that drives the fuel pump for leaks.

The next favorite suspect item according to my dealer's mechanics would be the emulsion tubes in the carbs. Those I haven't delved into yet.

 

[MikeD5172]

Mark1305,

Thanks for the info on the rebuild kits. It's info like this that helps everybody. I just wonder what the rebuild kit would cost from Ducati (if available).

Mike

 

[javadave75]

The rebuild kits will be the same Mikuni repair kits regardless where you get them. My problem wasn't because of the fuel pump but I now have a solid fuel pump from my rebuild

I talked to a Ducati mechanic and picked his brain about what could be wrong with my bike. He said with the hoses and pump all in good shape and with the fact I only have 6k miles, water in the fuel would be the most likely culprit.

So I will need to rebuild the carbs but before I do I am going to try some "HEET" in the fuel to see if it can pull out the water...if that doesn't work then I am going to play mad scientist this weekend. Wish me luck!

 

[just_ducky]

Don't know about you dying on the interstate, but so far as your occasional high idle goes I just picked up my 600M from its 10K tune up and after 20 minutes or so had an idle in the 2500 rpm range. they tweaked the idle screw when it was in the shop. Bike wasn't warmed up enough when they did the adjustment. Took it back the next day and they reset it. I found when it idled high it would only do it after the bike was well and truly warmed up, and I found if I lugged it when it was idling at 2500 it would then drop down to 11-1200 rpm. hope this helps. Good luck.

 

[Guest]

I saw in one of the replies in this post something about emulsion tubes in the carbs. Can anybody tell me what these are. I'm having the same problems that MANY others are having with a shitty running monster and I've tried everything. Even the Fuel pump rebuild kit that was described on here. Just curious to know what these tubes are, and if they are hard to rebuild, fix, repair, clean, etc...???

Thanks!!

 

[Guest]

I saw in one of the replies in this post something about emulsion tubes in the carbs.

 

[javadave75]

I have been one of the people on this list that put several posts regarding the duc dying. Good news my bike is up and running! The final fix that got her up and about was taking the carbs out and cleaning them. There was a bit of water in the carbs which is why I couldn't throttle. But something I couldn't see was the screw holding the main jet fell out and was floating freely in the float bowl! To me the loose screw was the biggest shock of all since I have only put 500 miles on the bike since the dealer jetted the carbs. Needless to say that Ducati shop/dealer isn't open anymore.