Gas pressure in thee tank... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

SiCk_DiAbLo · 08-05-2010, 12:58 AM

I was just curious...Why is it that 2 of my vehicles when ya open the gas cap ya hear that pressure releasing..Then on my truck, I hear nuthing...Is the cap bad, or is that normal...???

ChevLoRay · 08-05-2010, 11:39 AM

I don't notice pressure venting on my truck, but mines a CPFI where yours is a TBI. Doesn't mean mine is right and yours is wrong. On these vehicles with computers, OBDI and OBDII, leaving the cap off can trigger a Check Engine Light/Service Engine Soon light. So, my thinking is that if the cap is supposed to hold some sort of pressure to keep that light off, yours may not be bad....if you don't have the SES light. Do you?

SiCk_DiAbLo · 08-05-2010, 02:07 PM

Yeah the Service Engine Soon light pop's on and off from time to time...Already changed the 02 sensor...But thanks...I wunder if I changed caps would there be a difference..??

ChevLoRay · 08-05-2010, 02:17 PM

There's a gasket/seal on the cap that may have deteriorated over time and you might well benefit from replacing it. Easily done and not expensive.

08-05-2010, 12:58 AM	#1
SiCk_DiAbLo Registered User Join Date: Oct 2008 Location: Norfolk,Va Posts: 354	Gas pressure in thee tank... I was just curious...Why is it that 2 of my vehicles when ya open the gas cap ya hear that pressure releasing..Then on my truck, I hear nuthing...Is the cap bad, or is that normal...??? __________________ 1993 Chevy Silverado. 1984 Chevy Z28. 1972 Chevy Custom 10. 1965 Custom 10..FOR SALE

08-05-2010, 11:39 AM	#2
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: Gas pressure in thee tank... I don't notice pressure venting on my truck, but mines a CPFI where yours is a TBI. Doesn't mean mine is right and yours is wrong. On these vehicles with computers, OBDI and OBDII, leaving the cap off can trigger a Check Engine Light/Service Engine Soon light. So, my thinking is that if the cap is supposed to hold some sort of pressure to keep that light off, yours may not be bad....if you don't have the SES light. Do you? __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

08-05-2010, 02:07 PM	#3
SiCk_DiAbLo Registered User Join Date: Oct 2008 Location: Norfolk,Va Posts: 354	Re: Gas pressure in thee tank... Yeah the Service Engine Soon light pop's on and off from time to time...Already changed the 02 sensor...But thanks...I wunder if I changed caps would there be a difference..?? __________________ 1993 Chevy Silverado. 1984 Chevy Z28. 1972 Chevy Custom 10. 1965 Custom 10..FOR SALE

08-05-2010, 02:17 PM	#4
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: Gas pressure in thee tank... There's a gasket/seal on the cap that may have deteriorated over time and you might well benefit from replacing it. Easily done and not expensive. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.



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