80' Buick Century 3.8 N/A Bogging Issue

ck80 said:

Dumb question, but, when they're working on the carb, are they using modern manufactured, ethanol resistant parts for it and such?

Cause if they're using old stock carb kits and pieces, and, you don't burn ethanol free aka marine gas then you'll keep undoing the repaired work....

Basically if you need to keep having the work redone, there's a few common denominators, especially if it's the recurring problem. One answer is incompatable parts and fuel. Another is that they are getting things close, and, then tolerances continue to get worse and the problem returns - such as if the needle issues with bushing wear and they aren't fixing the bushings, just swapping needle size.... or, float is getting damaged by the ethanol and not working like it should.... so on so forth.

Edit: another would be which fuel lines were done... there's rubber lines hidden atop the gas tank between sending unit and metal lines that were not ethanol safe from the factory. And, not all rubber line sold by parts stores is ethanol safe either. If that line is getting degraded and sending debris to the carb.... or if the tank was never dropped and checked, has the fuel filter ever shown signs of crap being pushed to it...

Edit 2: another question would be if you're still running the efe unit (early fuel evaporation unit) it's like a thick gasket with wires coming off it between the carb and intake. They melt with age. You could have some sealing issue with the e.f.e. or a problem on the intake/carb surfaces that, when freshly put together, everything seals nice. As time goes by, something loosens and you wind up with a massive vacuum leak.

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ck80 said:

First and foremost, the e.f.e. unit was a gm attempt to improve cold start/idle issues on the automatic choke computer controlled carbs. It's like I said, it looks like a very thick composite gasket, ~3/16" or so with a pair of wires and plug coming off it. Embedded into it where the openings for the fuel/air mix to pass from carb into intake was a metal grid. On cold starts the computer would activate the grid which acted as a mesh heater to pre-heat the mixture. The grids would, over many years, melt away. Assembly order is intake, then efe, then carb on top. As you can imagine, it can be a source of vacuum leak since you're adding multiple layers of surface sealing instead of just carb direct to intake.

Based on your other info, I'd add two consideration points: 1) was the rubber line you replaced above the gas tank ethanol safe, or, just fuel line? Not all new rubber gas hoses are ethanol safe, although, fuel injection barrier hose usually is. 2) I'd drop the tank, pull the sending unit, and check the fuel sock. It's a $1 part, but, if there's dirt or debris in the tank it'll clog and restrict flow.

It's a cheap labor-only exercise that tells a bunch. When the car is shut off, and suction ends, debris can detached from clinging to the surface and flow is better. Start up again, and, it comes back. Especially if you're seeing stuff in a fuel filter anyways.

I had an 88 cutlass I bought that was so bad, the car would shut off after a few minutes due to starvation. Redid the tank/sock and problem gone. That was much worse than yours, but, I think if you want to narrow things down as cheaply as possible I'd drop tank, check sock, ensure rubber lines ethanol safe. Then unhook the rubber line to the fuel pump, blow out the metal fuel lines. Hook a long rubber line on the back to a glass jar of gas, hook the front line to a cheap HF transfer pump, and pull the gas through and look if it comes clear or is picking up junk. Then you know you've got good gas supply to the pump, and, all it takes is time to see if issues are present in that area.

I'd check the e.f.e. surfaces using some starting fluid sprayed while idling, cold engine. If the idle races, you know it's sucking in.

Then I'd chase my vacuum lines and make sure there isn't something cracked or broken anywhere, just to be safe. But the fact the problem goes away and returns over time steers me away from that.

It really sounds like you've got an issue elsewhere with a reassembly loosening up, or, an ethanol issue.

Fwiw, ethanol free fuel has higher energy content so while it's more per gallon, you use less (depending on driving style.) I only run ethanol free due to it both being much more corrosive, and, it's water introducing properties unless I'm in one of my late model vehicles AND on a road trip where I know the gas will be burned away in the next 48 hours.

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