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Old 04-30-2013, 08:46 AM   #1
dropanddrag71
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can my new gas cap be causing my truck to run bad.

70 3/4 ton automatic, 350...
My locking gas cap was old and the gasket material was weathered and cracked, so I went to the local parts store and got a new shiny chrome one. Truck runs bad after a while and the new cap has no vent, I screw it so tight not a drop of air can vent in, now, I realise all I have to do is run it with the cap off, but did I get the wrong cap and is there a differance?
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Old 04-30-2013, 08:55 AM   #2
cdowns
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Re: can my new gas cap be causing my truck to run bad.

yes a big differance in a vented and nonvented caps


your truck calls for a vented cap
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Old 04-30-2013, 08:58 AM   #3
Rufton
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Re: can my new gas cap be causing my truck to run bad.

I think you answered your own question.
Fuel tank must have a vent.
On some older vehicles the cap provides vent.
No vent affects fuel flow and engine operation.
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Old 04-30-2013, 09:37 AM   #4
68gmsee
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Re: can my new gas cap be causing my truck to run bad.

The reason the locking gas cap worked is because they don't fit real tight. I gave up on them when I lost the key. Played hell trying to remove it and if you drill the hole, it will drop stuff down to the tank.

The vented cap should have a small vent hole in the center that is slightly spring loaded to allow venting of gas fumes when cab is hot in the summers and the cap allows an inward flow of air when needed. If you can't find one locally try the vendors section under forums above.



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Old 04-30-2013, 11:29 AM   #5
dropanddrag71
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Re: can my new gas cap be causing my truck to run bad.

I will buy a new cap!
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