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Originally Posted by jarretts70
The car had a full-bore resto, so everything is new from the gas tank to the carb.
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Questions about this later.
Quote:
Originally Posted by jarretts70
That said, the fuel pump was nothing special, just a stock style replacement.
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Changed the mechanical pump on my 79 a few years ago. Sitting level, with a full tank of gas, I had to plug the line to the tank to keep fuel from running out. It siphons out because the line up front is lower than fuel level in the tank.
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Quote:
Originally Posted by jarretts70
.I didn't realize that modern fuel was that prone to evaporation.
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Think about how big the bowl is and how much of that is displaced by the float. Carbs stay cool when the engine is running. Heat soak after you cut it off, especially with a functional exhaust cross-over, and not all but most of the gas will evaporate in a hurry.
Quote:
Originally Posted by jarretts70
One other thing that might(?) be related - when I shut the car off after it runs for more than a few minutes I can hear gas running back into the gas tank. Residual fuel left in one of the return lines? Not sure if this is normal or not.
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The 79 gave me more trouble with fuel starving (after engine upgrade) Than any Pontiac I've ever owned. Electric pusher helped a lot but it still happened at the worst possible times. More gas the tank had in it...the fuel starve happened more often.
Smog era tank vent does not let enough air in the tank for what gas is coming out at WOT. Fuel pump was pulling a vacuum in the tank. Worse when full (because of less air space) and fuel would cover the vent line making it harder to let air in.
Adding old school vent and vented cap stopped the vacuum in the tank that the fuel pump couldn't over power.
On your car...Vacuum in the tank would/could be pulling fuel out of the pump through the return line when you cut it off. The factory vent line can also get fuel in it when the tank is full.
A lot of cars, sitting parked, would actually flood the carbon canisters when conditions were right. Like cutting the car off right after fill-up on a hot day. A nasty wet carbon canister will barely let any air go back to the tank.
Just some past expierence with this
Clay