Sucking sound when remove gas cap? Normal.
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Sucking sound when remove gas cap? Normal.
Is it normal to have the sucking sound when you remove your gas cap? When I was having my carb tuned at a local speed shop, I overheard a couple of mechanics discussing how important it was to have a non pressurized fuel system. I have looked and can not find a vented gas cap for the 77 250 with the tank behind the seat. Any thoughts would be appreciated. 77hb
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From: Albuquerque
Not sure on your ap but you have to have a vent somewhere. Probably at the charcoal canister/carb. Withouot it you will have either pressure or vacuum in the tank and that can cause carb like problems. It can also get you a face full of fuel when you pull the cap off.
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If you have a tank behind the seat than your truck was probably built before charcoal canisters and return fuel lines and all the other emission stuff. My trucks with the tank behind the seat usually have a looser fitting gas cap (if that makes sense) and I dont remember any sucking sounds. If the truck runs fine dont try to fix it. When the mechanics were talking about a non pressurized fuel system were they refering to newer cars with fuel injection?
Last edited by FordTrucksKickGM; Mar 2, 2006 at 09:48 AM.
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I would say it would Blow more than it would suck.
I get the gears all the time for telling people that the 78/79's DON'T have a vented cap.
Ford wanted it that way I suppose.
The air insde the tank expands on a hot day and BLOWS when you remove the cap.
I get the gears all the time for telling people that the 78/79's DON'T have a vented cap.
Ford wanted it that way I suppose.
The air insde the tank expands on a hot day and BLOWS when you remove the cap.
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From: South Bend, IN
The tank HAS to have a vent, either through the evaporative system or through a vented gas cap. My '76 has a vented gas cap. The caps have a one-way valve that allows air to enter the tank as fuel is sucked out of it, but not to allow gas fumes to escape. If the tank isn't vented, the fuel pump will pull a vacuum out of the tank as it empties, until it can't pull any more fuel, and the vehicle will die from fuel starvation.
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From: Kalispell,Montana
I'd relook for the venting somewhere,my thinking is if you are hearing air pulled in when you open the cap then you run the risk of collapsing your tank,not to mention the carb problems that could result.
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What do you think that Fuel Tank Vent Tube is for ?
Not all caps are vented on Ford trucks.
EDIT:
I just got back from
www.rockauto.com
you should see all the choices for Gas Caps for the 77 F-250
Not all caps are vented on Ford trucks.
EDIT:
I just got back from
www.rockauto.com
you should see all the choices for Gas Caps for the 77 F-250
Last edited by Mil1ion; Mar 2, 2006 at 04:27 PM.
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That sucking noise is the sound of your money leaving your pocket when you buy gas.
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Sorry for the confusion. I checked after reading the responses and you are correct, it is the air escaping from the tank, not being sucked in. The cap allows air in but not out. Perception vs reality sometimes. Thanks for the responses. 77hb
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