Diagnosing a fuel delivery issue and no longer identifying that mystery hose

[Jobu]

So I ordered the parts for a fuel pump rebuild.  I'll let everyone know how it goes and hopefully I'll take enough good pics to post up in the how to section.

I would've suggested an electric pump, but it can be a hassle to find a good mounting point.  Good luck with the rebuild, it should be simple enough.

However, definitely buy a manual fuel shutoff valve if your bike has the vacuum operated petcock.  Those things are prone to fail and if you haven't checked it yet, it might be part of the problem anyway as someone suggested.  The only good thing about the vacuum petcock is that it is automatic until it fails. 

I would suggest getting one of these:  http://www.motionpro.com/motorcycle/partno/12-0036

[Ducatista]

No love on the fuel pump rebuild.  She's still not running well.  She still won't take any throttle.

Does anyone know what the little round thingy is underneath the tank?  Not the fuel filter.  This is the view with the tank up and looking towards the tail right in the area of the hinge.  I'm touching the part in question.  Could it be the culprit?

[greenmonster]

It`s the petcock.
When malfunctioning, fuel just flows pass it, doesn`t shut off due to vacuum diaphagms bad inside.

[Ducatista]

So we found something odd.  The breather tube that goes from the tank to the mysterious canister under the seat was full of water.  I'm pretty sure that ain't good.  What would cause this?  We're still at the point where if it has been sitting for awhile, it will run fine.  As soon as you take it up and down the street, it dies under power.   

We did verify correct assembly and installation of the rebuilt fuel pump.  When you disconnect the hose and hit the starter, fuel does indeed come spurting out. 

[Jobu]

So we found something odd.  The breather tube that goes from the tank to the mysterious canister under the seat was full of water.  I'm pretty sure that ain't good.  What would cause this?  We're still at the point where if it has been sitting for awhile, it will run fine.  As soon as you take it up and down the street, it dies under power.   

We did verify correct assembly and installation of the rebuilt fuel pump.  When you disconnect the hose and hit the starter, fuel does indeed come spurting out. 

I'm not that familiar with the emissions system on these bikes, but I wouldn't think water should be in there unless it drains the air box and water got in the air box.  Other than that, I don't know where water would come from.    But I don't think that is your problem.

I don't remember if this has been mention yet, but did you check to make sure the tank is venting properly.  This sounds exactly like a venting problem that someone I know had recently.

[Ducatista]

I'm not that familiar with the emissions system on these bikes, but I wouldn't think water should be in there unless it drains the air box and water got in the air box.  Other than that, I don't know where water would come from.    But I don't think that is your problem.

I don't remember if this has been mention yet, but did you check to make sure the tank is venting properly.  This sounds exactly like a venting problem that someone I know had recently.

The tube doesn't go near the airbox.  I've tried running it until it dies and then popping the cap, and there is no suction sound and the bike will not restart until it has been sitting for awhile.  I'm not saying that's not the issue, but those are the symptoms I've observed so far. 

[Jobu]

The tube doesn't go near the airbox.  I've tried running it until it dies and then popping the cap, and there is no suction sound and the bike will not restart until it has been sitting for awhile.  I'm not saying that's not the issue, but those are the symptoms I've observed so far. 

Well, you can try running it with the cap open the entire time, that will rule that out, but I don't think that is the problem.

You need to make sure the needles in the carbs are properly raising.  This could cause a problem.  There are couple of ways to check this.  The easiest way is to take the air filter out and reach in and push the black slide in at the top of the carb.  If the slide returns, the diaphragms are good.  These are probably fine, but good to rule it out.

[Speeddog]

As a test, bypass the vacuum petcock, perhaps it's partially plugged or stuck nearly closed.

[ducpainter]

As a test, bypass the vacuum petcock, perhaps it's partially plugged or stuck nearly closed.

Just replace it with a manual one.

[Ducatista]

You need to make sure the needles in the carbs are properly raising.  This could cause a problem.  There are couple of ways to check this.  The easiest way is to take the air filter out and reach in and push the black slide in at the top of the carb.  If the slide returns, the diaphragms are good.  These are probably fine, but good to rule it out.

In the carb rebuild, we checked their function and they slid smoothly and returned as normal. 

[Ducatista]

As a test, bypass the vacuum petcock, perhaps it's partially plugged or stuck nearly closed.

In our testing, we took off the hose on the other side of the fuel pump, and fuel gushed out.  If the petcock was stuck partially or fully closed, we wouldn't have gotten so much fuel spurting out.  Please correct me if I'm mistaken!

[ducpainter]

So we found something odd.  The breather tube that goes from the tank to the mysterious canister under the seat was full of water.  I'm pretty sure that ain't good.  What would cause this?  We're still at the point where if it has been sitting for awhile, it will run fine.  As soon as you take it up and down the street, it dies under power.   

We did verify correct assembly and installation of the rebuilt fuel pump.  When you disconnect the hose and hit the starter, fuel does indeed come spurting out. 

If there was water in the emissions cannister the hoses under the tank are reversed.

Maybe you're feeding water into the vacuum line?

[Ducatista]

Ok, so I have a case of bad gas... uh, I mean... the bike had bad gas in the tank.  It hadn't been in there long before the failure, in fact Stillie had just gotten gas (*ding ding ding*) when the problems started happening.  So we drained what was there and it was bright dehydrated-pee yellow.  YUCK!!!  So poured some known good gas in.  Cough sputter wheeze, and she roared to life after several tries, working the bad gas through.  So then we get ambitious.  We take her for a spin on this little bit of good gas.  She dies after awhile.  There's still a bit of gas in the tank.  Hmmmm... we didn't run out of gas.  So we disconnected the spark plugs, unhooked the tubes, and drained some out.  VERY INTERESTING.  This bad gas floats.  No water, just the smaller bit of yellow ickness floating on the top.  So now comes the fun part.  We get to purge the entire system.  The bad gas floats, so every time we run low, this problem will occur unless we get every drop out from head to toe (or tank to carbs, as the case may be).

So the primary problem was the bad gas, the carbs were indeed thoroughly gummed, so that was secondary and needed to be done anyway.

This is the theory, at least. 

Anyone know what kind of bad gas floats?

[Bigbore4]

<snip>

Anyone know what kind of bad gas floats?  <snip>

Not to be a wise guy, but "not gas".

Water is heavier and would sink to the bottom, so is Diesel, but they would mix. 

Have kids?  Was someone playing "Gas Station".  My mom has a not even Super 8 (yep, another fossil) of me playing gas station with dad's new Merc!

Is all well after a thorough clean out?

[Ducatista]

Not to be a wise guy, but "not gas".

Water is heavier and would sink to the bottom, so is Diesel, but they would mix. 

Have kids?  Was someone playing "Gas Station".  My mom has a not even Super 8 (yep, another fossil) of me playing gas station with dad's new Merc!

Is all well after a thorough clean out?

Well, the clean out is going to happen tomorrow.  I'm keeping my fingers crossed that it will work!

It is whatever came out of the 89 octane pump the last time Stillie filled up.  No kids except the furry kind.  It also burns... kinda... but not well.