Skip to main content ↑ ↓
Topic: Diesel fuel tank building up a vacuum (Read 1150 times) previous topic - next topic
0 Members and 1 Guest are viewing this topic.

Diesel fuel tank building up a vacuum

Yahoo Message Number: 15931
Does anyone else's Diesel Gulfstream 's fuel tank build up a vacuum that gets released when you open the fuel filler cap? Mine is so bad it makes the oil canning sound from re-expanding. Replaced cap but didn't change it.

Re: Diesel fuel tank building up a vacuum

Reply #2 –
Yahoo Message Number: 15936
Mine has always had the vacuum. Even after changing filler cap.
Best
Ron Hall

Re: Diesel fuel tank building up a vacuum

Reply #5 –
Yahoo Message Number: 15940
There will always be some vacume but the cap relpacement will  keep at a minimum.

Re: Diesel fuel tank building up a vacuum

Reply #7 –
Yahoo Message Number: 15943
Thanks for all the responses! Helps me to know it's common on the gulf streams

Re: Diesel fuel tank building up a vacuum

Reply #9 –
Yahoo Message Number: 15949
Ok, so I checked with a Diesel fuel tank Engineer and got a definitive answer on this problem. The fuel tanks should NOT be building up ANY vacuum. They should be, by design, vented to the atmosphere to allow air in to the tank to replace diesel fuel as it's used up.

The repeated process of contracting and expanding the tank is not good from a structural stand point, and it may cause pre-mature failue of the fuel pump. It may also cause the engine to not be able to produce full power.

We suspect that Gulfstream used the production vent for the generator's fuel lines.

The suggestion was to tee into the fill tank vent hose and use an inline fuel filter to filter the incoming air to keep dirt out of the tank.

Hope this helps everyone.



Re: Diesel fuel tank building up a vacuum

Reply #10 –
Yahoo Message Number: 15951
Given the location of the vent, inside the fill tube, the cap should be a vented cap. Check my cap and it is a vented cap, so I don't understand how vacuum could build up in the tank, but it does.

I parked my Gulf Stream Sunday and haven't had it running since. I did however have the generator running earlier today for about 15 minutes, just went out and check the cap and there was vacuum present in the tank.
Not sure if the vacuum was left over from the last time I ran the MH or if was created by running the generator earlier today.
I'll run the generator again to see what happens and let everyone know.

Re: Diesel fuel tank building up a vacuum

Reply #11 –
Yahoo Message Number: 15952
Just for information. Our chassis does not have a fuel pump. The CP3 SUCKS fuel from the tank. Passing thru the fuel filter. It's not only Gulf Stream. All the Super C's on the C5500 with the Drama engine get the Vacuum. I also have seen vacuum build up after removing cap to let Vacuum out. Then check it days later and find Vacuum again. Never ran anything.
Best
Ron Hall

Re: Diesel fuel tank building up a vacuum

Reply #12 –
Yahoo Message Number: 15953
My 2007 c5500 had a fuel pump in the gas tank.

Larry Payne  ⛳

Re: Diesel fuel tank building up a vacuum

Reply #13 –
Yahoo Message Number: 15954
Ron, are you sure, I can see after sitting for a day or two, if the weather warmed that pressure could build in the tank. It's difficult when removing the cap to tell if

Re: Diesel fuel tank building up a vacuum

Reply #14 –
Yahoo Message Number: 15955
Sorry, fat fingered my phone and hit send before I was done.
Anyway, when removing the cap, it's difficult to tell if vacuum or pressure is being released.

Relative to the CP3 (aka fuel pump) are mounted on the Duramax engine and draw fuel, not push it like a typical tank mounted fuel pump. This by default creates vacuum and the tank needs to be vented to not over work the CP3.
Duramax have used this type pump since they came on the market in GM HD pickups. The CP3 is considered one of the weak links in an otherwise good engine, so much so, that there's many after market electric pumps that mount near the fuel tank that pushes fuel to the CP3. The addition of a electric pump (and filter) drastically improves the life of the CP3 and injectors for that matter.

Re: Diesel fuel tank building up a vacuum

Reply #15 –
Yahoo Message Number: 15956
I'm sorry guys, that was a sending unit in my diesel tank with a float that I adjusted to adjust my dash gauge. My vent was 90 degrees downward and only allowed 60 gals of fuel. I cut it off and raised it 2 1/2 inches. Gave me 80 gals.

Larry Payne  ⛳

Re: Diesel fuel tank building up a vacuum

Reply #16 –
Yahoo Message Number: 15957
Anything that moves the fuel is a fuel pump, even if it's engine mounted. So the CP3 is fighting that vacuum all the time because it has to pull fuel out of a tank that has a vacuum in it.

Either way the tanks should be vented to the atmosphere and shouldn't build up vacuum and especially not pressure. I'm wondering if this a contributing factor to the CP3's failures.....



Re: Diesel fuel tank building up a vacuum

Reply #17 –
Yahoo Message Number: 15958
Not sure you fix anything with a tank vent. I would be worried about sucking moisture and other debris even with a filter. The enemy of high pressure fuel systems is water.
Best
Ron Hall

Re: Diesel fuel tank building up a vacuum

Reply #18 –
Yahoo Message Number: 15959
No debris will get past the fuel filter. The hose routing will prevent water from getting in, just like a factory setup does. I'll post a picture when I'm done. There was no doubt from the fuel tank engineer that they should not be developing vacuum or pressure. Something is wrong with our current vent setup.