Quote:
Originally Posted by ChevyTech
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.
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I knew you were going to say that, because just like you said, what is happening DOESN'T make sense! The line that is leaking is the one that has the fuel filter on it, and it's leaking from the fuel filter (front) side.
Thanks for confirming that the gas cap SHOULD be non-venting (just making sure) and explaining that the venting is through the charcoal cannister. I'd forgotten about that. What if the line to the cannister got plugged up? I'll check that ASAP.
I'd like to know more about this weep hole--must have a check valve of some sort, right?--and to confirm that my Model 220 TBI has one. When I dismantle the TBI again, I will look for it, and inspect the new FPR to make sure the diaphragm is intact. Not sure how to test the diaphragm outside the unit, though. It COULD be leaking in the middle where the steel plunger is. I was amazed how flimsy these are, just two thin layers of red rubbery stuff, whatever it is.
I suppose that since somebody altered the fuel line by cutting in a piece of hose, they might also have done other "stuff" to the gas tank. Looks like I'm gonna have to drop the tank, pull the sender and take a look inside and "see what I can see". This will have to wait at least a week.
The only other thing I can think of is if they swapped the fuel lines somewhere in the middle, which seems darn near impossible. As you said, the return line is SMALLER than the supply line, not to mention the fact that these are HARD LINES and resist moving around. I could barely move them where they connect to the TBI, and I've already verified that they are connect properly to the throttle body.
Will report back later. Thanks!