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Vacuum Pressure in Fuel Tank(again)??

Yahoo Message Number: 56060
I posted a few days ago about the vacuum pressure in the Fuel Tank and several including Mikee said there should be no pressure...So I pulled the inspection plate to the tank and There is no medal pipe coming out of the tank, nothing that looks like a vent... there are several rubber lines connected that run up and under the floor. Does anyone know the real story here...I sure would like to know for sure..
Marvin, 07 Allure 470, 31459

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #1 –
Yahoo Message Number: 56062
Marvin, my Allure is an 06, but should be the same as your 07. On the drivers side of the coach I have a small metal tube (maybe 3/16 inch in diameter) that is attached to the front of the fuel tank. You have to lay on your back partially under the coach to see it. I have no idea where it attaches or goes into the tank, but it is there.

R. D. Vanderslice
06 Allure 470 31294

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #2 –
Yahoo Message Number: 56064

Thanks RD, I will look tomorrow., see if I can find that tube..., I on both sides the vents that return into the filler neck., but I cannot see any other tube that look like a vent that goes into the top of the Tank, but I plan to get to the bottom of this adventure..Thanks again, Marvin


From: R. D. Vanderslice To: Country-Coach-Owners@yahoogroups.com Sent: Fri, January 29, 2010 9:53:16 PM Subject: Re: [Country-Coach-Owners] Vacuum Pressure in Fuel Tank(again)??

Marvin, my Allure is an 06, but should be the same as your 07. On the drivers side of the coach I have a small metal tube (maybe 3/16 inch in diameter) that is attached to the front of the fuel tank. You have to lay on your back partially under the coach to see it. I have no idea where it attaches or goes into the tank, but it is there.
R. D. Vanderslice
06 Allure 470 31294

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Re: Vacuum Pressure in Fuel Tank(again)??

Reply #3 –
Yahoo Message Number: 56067
Marvin,

I am also having a problem with the real story. Yesterday here at the National Wildlife Refuge we took delivery on a brand new 6430 John Deere field tractor. It is fairly large tractor but not one of the monster jobs. In tractor terms it is 95 hp.
Anyway today I took it for about a 5 min test drive (sweet machine) and before putting it to bed I noticed that it came with just about an empty tank. I pulled up to the diesel tank to fill it and when I removed the fuel cap the tank was under vacuum.
Hard to believe that a new tractor would have a blocked fuel vent but maybe so. My coach fuel tank is under vacuum every time I fill it and it is over 6 years old. Its performance seems normal and not starved for fuel and the mileage is about where it should be.
Every time I fill it the vacuum seems about the same. I am beginning to wonder if the tank is a closed system like a gas engine. Is it under a constant vacuum up to a point and then the fuel cap relieves it to keep it there? Just don't know but something here is not adding up for me.

Don Seager

2004 Allure 31046

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #4 –
Yahoo Message Number: 56068

Don I'm beginning to feel like you, I'm not so sure if it is not suppose to have the vacuum..I have learned to remove cap real slow and let the pressure equalize.., Maybe Cummins would know... will try them next week... Marvin

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #5 –
Yahoo Message Number: 56070
Marvin,

It may be a matter of who you talk to at Cummins sort of like talking to Verizon tech. Just keep calling until you get one that says what you think makes sense. I would be interested in what you find out.
I know that most fill pipes have a vent to relieve the pressure as you fill the tank. That is supposed to stop the fuel from belching back at you as often a fast fill will completely fill the tube causing pressure in the tank that has nowhere to go. It is like the tube in the manual fill inlet for a fresh water holding tank.

But a running tank vent? Many say so but a lot can't find it.

Thanks for the response.

Don Seager

2004 Allure 31046

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #6 –
Yahoo Message Number: 56073
They may have used a rubber line for the vent line. You are going to have to determine where each lines goes, or try it the other way, look around the bottom of the tank for the open end and follow it back.

Mikee

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #7 –
Yahoo Message Number: 56082
Friends,

Just a thought my Dynamax Chassis 3 ring binder shows graphic illustration of the fuel tank, fuel fill lins, vent lines, overflow tube, fuel supply line, fuel return line, generator supply line, generator return line and fuel tank sensor.

Thanks, Mike 03 Allure 1st Ave #30898

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #8 –
Yahoo Message Number: 56100
Marvin, In my owners manual in the "Parts" Section, under the "Engine Group, Fuel System 1.52" on page 1.54 there is a drawing that shows the "Fuel Tank and Components" Item 5 is the "Tube, Overflow (vent line). Yours may be on a different page, but if you look I'm sure you can find it and verify that you do or do not have a "Overflow tube, vent line".

Earl Densten

03 Intrigue 11554

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #9 –
Yahoo Message Number: 56107
Maybe it is supposed to have a vacuum but my '04 Allure has never had either vacuum or pressure.

George in Birmingham
'04 Allure 31038
George in Birmingham
2003 Magna 6298

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #10 –
Yahoo Message Number: 56119
Hey George,

I don't know if it is normal or not. All three of my Allures had it but that don't make it normal. Surprised me that our new tractor also pulls a vacuum.
Having the fuel cap say "vacuum only' doesn't help but that doesn't make it normal either.
I have never had a problem that was bad enough to notice. However having driven this coach for over 6 years, on my next trip I am going to drive it with a hole drilled in my spare fuel cap to see what if anything changes. Blocked breather lines or whatever I will know that the tank is vented. We will see.

Still planning to come our way?

Don Seager

2004 Allure 31046

Re: Vacuum Pressure in Fuel Tank(again)??

Reply #11 –
Yahoo Message Number: 56130
There are 3 types of fuel systems... Vacuum, open, and pressure. The newer you engine the less likely it will be an open fuel system. the 07. 08 and up are trending to closed systems. Cars went to closed systems when the EPA mandated fuel evaporation and fumes were included in the emissions figures. If you remember some years ago all cars went to 7500 mile oil changes unless you drove in extreme conditions. When you read the parameters for extreme conditions you realized no one could drive in normal conditions. The reason the oil change interval was extended was because the waste oil got included in the total emissions figures, so they all just upped the oil change interval.

Mikee