The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 89 S10 4.3 Need help troubleshooting TBI/IAC Idle issue

ChevyTech · 08-26-2014, 04:17 PM

Gas caps on today’s automobiles are not vented. It has been that way for decades. The venting is through the charcoal canister.

My guess is you are miss-understanding or miss-stating what line the gas is coming from or which line is which, because it does not make sense, unless someone has modified the fuel sending unit in the gas tank.

Some TBI units do have a bleed hole so gas can bypass the regulator at a slow rate. This would explain the gas getting by the regulator but how it would get up to the return tube in the tank makes no sense.

08-26-2014, 04:17 PM	#48
ChevyTech Registered User Join Date: May 2004 Location: Minnesota Posts: 4,620	Re: 89 S10 4.3 Need help troubleshooting TBI/IAC Idle issue Gas caps on today’s automobiles are not vented. It has been that way for decades. The venting is through the charcoal canister. My guess is you are miss-understanding or miss-stating what line the gas is coming from or which line is which, because it does not make sense, unless someone has modified the fuel sending unit in the gas tank. Some TBI units do have a bleed hole so gas can bypass the regulator at a slow rate. This would explain the gas getting by the regulator but how it would get up to the return tube in the tank makes no sense. __________________ For those of you that are wondering why you are not getting replies to your thread: Did you give the model, year, engine, fuel system type, and transmission information? If it is modified from what came stock from the factory, let us know that too.