Gas-starved with half a tank

[The guy with the Ducati]

Hello everybody,

I have a '96 M944 with flatside carbs.

I just got my bike out of winter storage this week. Tank is stored empty, carbs drained, as always. She started up without much ado. Filled the tank, and away I went. The riding was fine, then while I was out at one point, she stalled out like I'd run out of gas. A little fiddling and I was able to get it started. I assumed perhaps some "gunk" (the technical term) in the tank after the winter. Anyway, I filled up again, taking less than 10 litres, and the bike ran fine.

Just now, however, the same thing happened. I filled up again, perhaps 8 litres, and she's running just fine.

So, that two tankfuls running into difficulties around the halfway point.

Anyone see a pattern in this? I haven't looked closely at the issue, but suggestions from a far-more-knowledgeable source are most welcome 

Thanks,
Steve

[Ddan]

Fuel pump?  A full tank might give you enough pressure but half a tank is lackin' gravity? 

[koko64]

Hello everybody,

I have a '96 M944 with flatside carbs.

I just got my bike out of winter storage this week. Tank is stored empty, carbs drained, as always. She started up without much ado. Filled the tank, and away I went. The riding was fine, then while I was out at one point, she stalled out like I'd run out of gas. A little fiddling and I was able to get it started. I assumed perhaps some "gunk" (the technical term) in the tank after the winter. Anyway, I filled up again, taking less than 10 litres, and the bike ran fine.

Just now, however, the same thing happened. I filled up again, perhaps 8 litres, and she's running just fine.

So, that two tankfuls running into difficulties around the halfway point.

Anyone see a pattern in this? I haven't looked closely at the issue, but suggestions from a far-more-knowledgeable source are most welcome 

Thanks,
Steve

I would have to agree with Dan that the fuel pump is acting sus. If you want to fix the pump just buy a Mikuni replacement for it at nearly the price of a rebuild kit.

I also once had similar symptoms with a blocked fuel filter. A full tank helped the gas squeeze through but at about half a tank it would die. You sound like you are on top of that though.

By the way I bet your bike is strong with that 944/ hi comp kit and FCRs.

[ducpainter]

I'd sooner suspect a dirty filter than a bad pump.

[transplant]

Sometimes pulling up the gas tank will kink your tank vent lines. If it does it again, open your gas cap. If it starts after that, your tank is not venting.
Another thing to check is the make sure you have the correct fuel filter. I use the Fram on my '95. I replaced it one time with what I thought was the correct filter, turned out the out part of the filter was on the opposite side, putting the gas line right on top of the valve cover. When the valve cover got warm, it would heat up the gas line and it would
shut off the flow of gas. Finding that drove me nuts for a couple of weeks.

George

[koko64]

I'd sooner suspect a dirty filter than a bad pump.

Hey Ducati Guy

Hmmm, a dry tank can get flakey, and when you put gas in it after a long break it can 'shed' a rusty layer clogging a filter.
I went through 3 fuel filters in 1000 miles untill it cleared. My bike was sitting around before I purchased it.

DPs right, do the cheap, easy fix first.
DP.
Sound like fuel pump failures are not uncommon in the States. Is it the Ethanol or some other additive in the gas there? In Oz I haven't heard of one vacuum pump failing and I'm guessing it's a rare thing. Ethanol is a recent thing here and only in some fuels as advertised.

[ducpainter]

<snip>
DP.
Sound like fuel pump failures are not uncommon in the States. Is it the Ethanol or some other additive in the gas there? In Oz I haven't heard of one vacuum pump failing and I'm guessing it's a rare thing. Ethanol is a recent thing here and only in some fuels as advertised.

Other than on here I've never heard of or seen a bad pump myself.

I know my buddy the vet has never seen one in his 13 or 14 years as a tech.

Ethanol is relatively new here so that may turn out to be a cause of pump failure, but I think that there has been a bunch of misdiagnosing up to now

[Howie]

I recently took my pump apart.  The diaphragms are stretched and there was some gasoline on the vacuum side.  Since the problem happens when the tank runs down to a consistent level leads me to think fuel pump. 

[moto-zen]

I'm gonna side with the fuel filter train of thought. It's always best to start with the simple and cheap possibilities and work your way back.
By the way, when storing a bike it's always best to have a full tank with some stabilizer added. This prevents rust in the tank and drying of the fuel lines.

[Porsche Monkey]

Other than on here I've never heard of or seen a bad pump myself.

I know my buddy the vet has never seen one in his 13 or 14 years as a tech.

Ethanol is relatively new here so that may turn out to be a cause of pump failure, but I think that there has been a bunch of misdiagnosing up to now

Ive had a vacuum fuel pump fail.  Replaced it with an electric one.

[The guy with the Ducati]

Thanks for all the great advice. I'll work my way up the list. Sometimes it's the simple things ... which is good, because they're usually less expensive