Fuel tank pressure buildup - Ducati Supersport 939 Forum
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post #1 of 14 (permalink) Old 04-21-2019, 06:34 PM Thread Starter
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Question Fuel tank pressure buildup

I took the SS for its first long ride today after two weeks of ownership. When I returned home, I noticed a faint whining noise after I turned the engine off but I figured it was a relay or an electrical component. I took off my gear and came back to check (about 5 mins) and she was still whistling! Zeroed in on the gas tank and opened the fill cap only to hear a pronounced suction noise. Now I know it is normal for a certain negative pressure to build in the tank when running but I also know there are devices that are supposed to mitigate that.

I've never had this happen on any of my other bikes, is this normal for a SS? I looked up my VIN on my Ducati and have 0 recalls pending.

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post #2 of 14 (permalink) Old 04-21-2019, 07:01 PM
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I have had this and I think it continues. Asked the dealer and they said it normal.
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post #3 of 14 (permalink) Old 04-21-2019, 08:24 PM
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Doesn't sound quite right, as you said it shouldn't be quite as pronounced. you might want to check the overflow tube at the bottom of the fairing mine had come loose and had melted shut as it was touching hot parts. Check if it is blocked, also then open your cap and tip some fuel into the overflow hole and see if it disappears and comes out the bottom of the tube, we get mud wasps here that love blocking up those holes, you cant do any harm in trying to understand it yourself.
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post #4 of 14 (permalink) Old 04-21-2019, 11:54 PM
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Doesn't sound quite right, as you said it shouldn't be quite as pronounced. you might want to check the overflow tube at the bottom of the fairing mine had come loose and had melted shut as it was touching hot parts. Check if it is blocked, also then open your cap and tip some fuel into the overflow hole and see if it disappears and comes out the bottom of the tube, we get mud wasps here that love blocking up those holes, you cant do any harm in trying to understand it yourself.
which side it the overflow inlet?

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post #5 of 14 (permalink) Old 10-22-2019, 06:01 AM
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Just experienced this myself - a singing petrol tank!
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post #6 of 14 (permalink) Old 10-22-2019, 06:14 AM
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It's a quite common sound on Ducatis. Many will do it when you garage them after a run. The tank breather is routed internally to a grommet under the filler cap which it seals against when the cap is closed. The tank then breathes through the filler cap assembly. The passageway must be very small and seems to lead to various squeals, chirps and other noises from many but not all bikes.
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post #7 of 14 (permalink) Old 10-22-2019, 09:18 PM
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Quote:
Originally Posted by klev View Post
I have had this and I think it continues. Asked the dealer and they said it normal.
Quote:
Originally Posted by Derek View Post
It's a quite common sound on Ducatis. Many will do it when you garage them after a run. The tank breather is routed internally to a grommet under the filler cap which it seals against when the cap is closed. The tank then breathes through the filler cap assembly. The passageway must be very small and seems to lead to various squeals, chirps and other noises from many but not all bikes.
Both of these are my experience as well, especially when I really get the bike good and hot and have been on it a while. It’s more pronounced certain times than others but I’ve been told it’s normal.

Mike

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post #8 of 14 (permalink) Old 10-22-2019, 11:06 PM
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Tank suck on Guzzis can cause fuel starvation and hard starting. I can't imagine it's good for the fuel pump.

It might be smart to open the gas cap to equalize the air.

I wonder if any Duc experts here know if the tank venting system is an issue? I've noticed that my tank will burp a little gas out of the cap when I fill it on a hot day.

John L

Last edited by LowRyter; 10-22-2019 at 11:09 PM.
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post #9 of 14 (permalink) Old 10-22-2019, 11:58 PM
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Doesn't sound right to me. I will park it in the garage after a 90 minuet run and nothing. I'll even open the cap and no pressure ever on the SS. Maybe because it's empty at this point. My 1098 gets pressure sometimes but never the SS.

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post #10 of 14 (permalink) Old 10-23-2019, 04:15 AM
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I have not experienced this either, in conditions with extreme variations in temperatures and weather conditions.

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