[Bootysmak]

I was cruising along on the parkway at about 85 and suddenly my bike totally died. It felt like I had switched it off, I mean it wouldn't even sputter. So I coasted to a stop and tested to see if it was getting juice to the plugs. When I was turining it over with the plug wire off, (a spark jumping between a screwdriver and the top of the plug) it sputtered a little. So I choked it all the way and turned it over for about 30 seconds, then it started. It was fine the rest of the way home. Could it have been the fuel pump? Wouldn't it have sputtered a little before dying if it was a fuel issue? Is there some kind of electrical problem that could have made it act like this? Thanks, Jake

 

[Speeddog]

What Monster do you have?

Carb'ed, injected ?

 

[Bootysmak]

It is a 98 750 carbed, open airbox, I'm at sea level.

 

[Speeddog]

If it was the fuel pump going bad, it would have tapered off and sputtered or surged as it emptied the float bowls.

Probably an electrical issue. Does your bike have the sidestand switch?

Did everything go off, lights and all?

 

[Bootysmak]

There is no side stand switch. The lights stayed on. One more thing that I forgot to mention is that I switched it off, then back on before it started to sputter again. When It initially died, I left it switched on, so that the lights would stay on, I could try to start it etc. I turned it off, when I was taking the tools out of the seat, then I switched it back on to see if juice was getting to the plugs.

 

[ScottRNelson]

There have been occasional problems with pinched fuel lines when the tank is raised and the fuel line is in the wrong place when the tank is put back down. There can also be problems with the breather hose being blocked so that there is a vacuum in the tank.

When cruising along on the freeway (sorry, I just can't bring myself to say "parkway"), you often don't get much warning when the carburetors go dry.

You have to crank the engine 20-30 seconds to pump enough fuel into dry carburetors before you have enough in there to start the engine.

 

[Mark1305]

Don't be too quick to rule out the fuel pump. Mine went out last March due to stretched and hardened diaphrams. The firstof many times it shut down that day it just died like you described while I was running about 35-40 in traffic rolling into South Daytona (first ride up to Bike Week, of course!)

After that it shut off due to vapor lock every time I got in slower traffic trying to get it 70 miles back home.

Do a search for fuel pump stuff on here - I've posted several times as have others. Rebuild kit is available for about 5.99 plus same for shipping. Overhaul takes about 30 minutes.

It's a cheap way to eliminate either the problem you have now or the problem you will have sooner or later.

 

[Bootysmak]

Thanks for the ideas guys. Scott, I'm from the west originally too, so it took me a bit to get used to distinguishing the parkways from the freeway. At the end of the day though, I really like the parkways cause there aren't any trucks allowed. I'll look into the fuel pump rebuild.

 

[Bootysmak]

Okay, So I had the problem again, this time a pulled the fuel line off of the tank. There was definately a vacuum in the tank. As the line got loose, I could hear the tank sucking in all kinds of air and bubbling up. So which Line do I need to check? There are 2 lines that look like they are vent lines. Thanks, Jake

 

[mnztr]

How old do the pumps get before they typically fail. I have a 1995 and it's still running well.

Mark

 

[Speeddog]

Okay, So I had the problem again, this time a pulled the fuel line off of the tank. There was definately a vacuum in the tank. As the line got loose, I could hear the tank sucking in all kinds of air and bubbling up. So which Line do I need to check? There are 2 lines that look like they are vent lines. Thanks, Jake

Assuming the layout is the same as my '02 S4 (which is a bit if a stretch...as your bike is carb'ed and mine is FI) the outer hose is connected to the drain for the fuel filler area, and the inner hose is the breather for the tank, and is connected to the rubber seal neck that mates with the filler cap when it closes.

As a definitive check, blow into the end of the hose with the filler cap open, and you can feel with your fingers as to which it is.

Some folks have had problems with the vent passages in the filler cap getting plugged up. They've said the passages are quite small. I've never disassembled mine, so I have no FHE.

 

[test-reg]

Bootysmak, you now know you have a vent problem. either a vent line is kinked when the tank is down or there is an obstruction or misalignment in the vent under the gas cap.

mnztr, too many variables. sitting and some fuel additives shorten the life of the diaphragm. not a bad idea to rebuild before you have a problem.

From my invoice for the Pentagonal shaped fuel pump rebuild kit

Manufacturers Supply Co.
Dorchester Wisconsin 1-800-826-8563

Part Number 451457

Part: $5.99
Freight: $5.99


from another post, so i can't take the credit.

 

[Bootysmak]

Ok, Thanks a lot guys. --Jake

 

[Mark1305]

mnztr,
I started the campaign against worn out fuel pumps, and Howie's posted the source for the cure.

To answer your questions about symptoms (and they will probably vary) - The only clue I had was when the bike vapor locked and quit. But, there were symptoms that went unrecognized until the fix - the bike ran strong and would go to top end. But, it surged and bucked at off-idle "parking lot" speeds and didn't like lugging below about 68-70 mph in 6th gear (with stock sprockets). These are accepted as normal behavior by a lot of Ducatisti - part of the bike's personality.

After overhauling the pump, I immediately noticed improved low speed driveability and suddenly the bike would run as slow as 60 mph in 6th gear without complaining or that lugging feeling.

My theory is that since the pentagon pump is rated for about twice the fuel flow the 900 requires at max hp, a dying pump can still flow enough. But what probably happens is that the delivery pressure is falling or erratic as the diaphrams get stretched and hardened. High end carbs like Webers and Mikuni CVs are sensitive to delivery pressure at the float bowl and it can affect metering accuracy.

This was reinforced in my case by spark plug readings. Before the pump fix, around town riding resulted in carbon fouling and highway trips results in clean normal plugs - I blamed it on the jetting and lived with it. After fixing the pump, the plugs are textbook perfect no matter what kind of riding I've done.

After checking for pinched hoses and clogged vents, the fuel pump is the next easiest and cheapest thing to eliminate from the suspect list before getting into the carbs. If that doesn't fix it, then you know the system is good up to the carbs, and you can tear into them.

Good luck

 

[test-reg]

Mark, your name is now with the fuel pump info so you can get credit in the future. that bit of info will save board members a small fortune.

 

[daniel]

Hey guys, had the same prob on my 95 900.
I could only get up to traffic speed 50-60 km/h, but no more and hills were out or the question. yeah the pump still worked but only just. I had me stumped for a while as the bike has only done 20k. might have something to do with the age of it I rekon as the diaphram had a tiny split which was also letting fuel into the rear cylinder.
Daniel.