Pressure in fuel tank

[Archive]

When I remove my fuel cap there is a good deal of air pressure released. During the warm months, I thought it was the heat-expansion of the air in the tank--but it’s cold now and the same air release occurs when I open the cap. Is this normal for this engine?

BTW, I just replace the fuel hoses a month ago--no change the air release.

Thanks.

------------------
'95 2500 SLT LB 2WD, auto 3. 54, 68,000--Westech gauges, Prime-loc, Brite box, Back-off Box, Line X, Flowmaster muffler, Borgeson steering shaft

 

[Archive]

Check to see if the little red cap on the fuel tank vent has been removed or if the tube is clogged. Where I live we have leaf cutter bees that love to plug small holes,at times they will plug every AC outlet ground hole in my shop. The vent is located on top of the fuel tank module,if the cap has been removed run a small piece of wire down the tube to make sure it isn't clogged.

 

[Archive]

Kodiak If your taking your cap off when tank is almost empty/half empty there could be pressure being released. Your fuel caps keep tank pressurized to 2. 5 psi(cap is rated 2. 5 psi). When tank is full you could run your engine with out cap but as you get low on fuel you need the system pressurized or fuel pump can't get enough fuel to injector pump(another words engine would run like crud or stall out.
BTW chrysler gas caps are the same pressure rating(of course in gas tanks it's gasoline vapors that escape when gas cap is removed).
There is a roll over valve on top of tank that also releases pressure but can't find any reference to psi. BTW I thought I read caps were rated for 25 psi. Need to check that out. Caps are pressure-vacuum, the vacuum release is between . 14 and . 29 psi as stated in service manual.

 

[Archive]

Thanks for the response.
Is there a locking fuel cap that is pressure-rated for this truck?

Thanks again!

 

[Archive]

Kodiak
Yes, any Auto Part Chain or local parts store should have one. Your preference of which one.
Of course Dodge would have them too, but mite be pricy. Call around for prices, range from $10 + to $25 +.
I bought mine at Discount Auto but it is south east chain.

------------------
Missouri Mule 96 White 4X4 ST club cab,(grey int. ),5 spd, 3. 54 reg dif, 8 ft bed, 1 ft high cheater boards, front and side of bed,Pofile V bug shield,
99 Freight liner FL60 blue Cummins 24v 215 hp, 520 torgue,6 spd 3. 59 no spin rear, 16 ft dry box (white) 19. 5 low profile tires,Weight 11,000, gvw 23000, 11 to 12 mpg
Bill Thomas (Wild Bill)

 

[Archive]

Originally posted by Kodiak:
When I remove my fuel cap there is a good deal of air pressure released. During the warm months, I thought it was the heat-expansion of the air in the tank--but it’s cold now and the same air release occurs when I open the cap. Is this normal for this engine?

BTW, I just replace the fuel hoses a month ago--no change the air release.

Thanks.

Are you sure that it is pressure or a vacuum of air rushing into the tank? I am sure it is the latter. My reason for this is that I have an auxillary tank installed in my 96 3500 and I have it emptying into the main tank. I drive down the road and fuel is pulled out of the rear tank and siphoned into the main tank. Another way to look at it is the sides of the tank pull in until you release the cap.

I hope this help with your question


------------------

 

[Archive]

Now that's an interesting thought. Thanks, George. I'll pay close attention next time right after running.

 

[Archive]

I have a whistle coming from my tank hours after its been run. The dealer has replaced my cap, but its still there. Once I crack the cap, it goes away. Ive tried running it loose, but it makes a **** of a mess on the side of my truck. Im beginning to consider just ignoring it. I have so many other problems with this wonderful $38,000 toy, I think my time spent counting the days until I get the guts to trade it off for something else will be better spent. Ive never owned any car, truck, etc that has given me as much grief as this Dodge Cummins. For the record, my 1982 Olds 5. 7 diesel spent only 2 days in the service dept in the first 100k miles, unlike my 98 Dodge. I think Ive hit the 65th day out of service last month and thats in just 18 months. Three cheers for Chryslers 5 star dealers! In think they get brownie points for how many repeat trips they can get out of you!

------------------
98 Quad Cab 4X4 Cummins Automatic Totally loaded Minus fuel sender plus right brake pull, no extra charge!

 

[Archive]

whats wrong with the word **** ? Dosnt that rhyme with Dodge?

 

[Archive]

My 97 has done this since new. I am pretty sure the pressure in the tank is less than ambient.
My wife's 98 has never done it.
I wonder if it hurts performance?

------------------
1997 4x4 CC 5spd, CPL1553 pump, Horton fan, Sport headlamps, Optima RedTops, 98 shift levers and console, RS5000 shocks, red light on dash (vol. FF)... .