Fuel tank vent

[Diesel Dually]

Is the fuel tank vent supposed to keep the tank from over pressurizing, or is it there to keep the tank from creating a vacuum while the truck is running?
My fuel tank seems to have a lot of suction when I remove my fuel cap. The less fuel I have in the tank the more suction there is. I don't remember it doing this up until about three months ago, but they say the memory is the first to go...

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`96 3500 4x4, JRE Stage 3 kit, JRE 4" exhaust from turbo back, low stall speed torque converter, shift kit, K&N air filter. Fisher EZ V snowplow. Towing Jackson 3 horse gooseneck w/ dressing and tack rm. , or 9 ton equipment trailer w/pintle.

 

[illflem]

Think the vent on top the fuel tank module allows vacuum to escape while the fuel cap allows pressure to escape. Mine always lets pressure escape when I open the cap.

 

[pwr2tow]

The fuel filler cap lets air in to depressurize the tank, I think the one on the tank does the same thing.
Make sure there is no cap on the tank vent, sometimes they forget remove the cap after installation. Regards, Ron

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1999, 3500, 6x6, slt, auto, 3. 54, Qd cab, ISB cummins, towing 2001 26RKSS Tahoe 5th wheel, 1999 120hp 1800 bayliner.

 

[Steve St.Laurent]

I've been wondering this same thing. I also get a wooshing sound (not sure if it's in or out) when I unscrew my cap. I have checked for the cover on the rollover valve and it's not there (checked again today). My tank has never looked caved in so I'm guessing that it's air rushing out of the tank.



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-Steve St. Laurent - President of the Great Lakes TDR
'98 QC LB (CMNSPWR), 4x4, ISB, 5sp, 4. 10 LSD, TST Powermax, 275hp RV injectors, Joe Donnelly modifed Sachs Clutch, custom ladder bars, SW fuel pressure gauge, BD exhaust brake, Isspro turbo temp monitor, front Draw-Tite receiver, rear Draw-Tite class V receiver, BFG 285/75R16 AT KO's, (all the common stuff clipped)

 

[HEMI®Dart]

In the 6 years I have owned the truck ,I have never had even the slightest hint of vacuum or pressure when I removed the fuel cap.

Go figure



[This message has been edited by HEMI®Dart (edited 02-24-2001). ]

 

[pwr2tow]

it is vacum, the cap lets air in after so much vacum. it's there so if the truck rolls over fuel will not leak out and become a potential fire hazard, but still let air in or else the vacum will collapes the tank, the one on the tank is the same.

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1999, 3500, 6x6, slt, auto, 3. 54, Qd cab, ISB cummins, towing 2001 26RKSS Tahoe 5th wheel, 1999 120hp 1800 bayliner.

 

[illflem]

The cap also releases pressure if it exceeds 2-2. 5 psi.

 

[CoastyAV8R]

On my 2001 ETH I noticed my tank had a suction on it when I opened the gas cap for the first time. I crawled under the truck and found the vent port still had the cap on it. After I removed it, no more suction on the tank. I talked to a Dodge mech who was the dealer Cummins guy and he said the tanks are suppose to be vented to the atmospheric pressure. I also put a piece of hose with a filter on mine and ran it up into one of the bed braces to ensure to road grime got into the fuel tank. My cap was red but I have heard that some are black. The port is located on top of the tank and points inboard towards the driveshaft.

Good luck
Pat

 

[madams]

For those still wondering where the tank vent is located . . enjoy!

On my 2500 Long Bed . . the best view is from the passenger side rear wheel well. Stick your head up in there and look between the frame and bed . . a little forward of the fuel filler neck.

#ad


This view is under the cab from the passenger side again . . right up under the muffler . . look up past the drive shaft.

#ad


My cap was already removed. No noticable hissing from vacuum or pressure.

Michael

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00 Driftwood 2500 ST QC ISB LB 5spd 3:54 LSD Tow & Camper Groups . . SunnyBrook 33FKS Travel Trailer

my photos

[This message has been edited by madams (edited 02-25-2001). ]

 

[Diesel Dually]

Thanks everyone for all the great responses. I'm going to check the vent asap... And try a new fuel cap.

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`96 3500 4x4, JRE Stage 3 kit, JRE 4" exhaust from turbo back, low stall speed torque converter, shift kit, K&N air filter. Fisher EZ V snowplow. Towing Jackson 3 horse gooseneck w/ dressing and tack rm. , or 9 ton equipment trailer w/pintle.