Buick Stalls When Gas Tank Is Less than Half Empty

I have a 1995 Buick Century 3.1 wagon that suddenly started stalling when the gas tank was at half or less. Mechanic has tested the fuel pump and fuel injector and they appear to be fine. The stalling can happen when I’m on the highway or standing still. Sometimes the car can start right up again, but other times it is a minute or so before I can start it again and have it run properly. In the meantime it barely chugs along as if no fuel is getting to the engine. Then it suddenly can start again as if nothing was wrong, and run fine until the next stall. Any ideas as to what could be wrong?

Do you keep track of your miles per gallon or miles per tank? Do you know how much it normally takes to fill the tank? Your sending unit could have become inaccurate and you are in fact running out of gas. This suggestion need not apply if you normally keep track of these things, but there are many people who don’t, so I’m suggesting this as a possibility. This is also a common way for a sending unit on a GM to go bad.

I had a similar problem with a '91 cad. a few years ago. It turned out to be the fuel pump. I had it checked by my good friend mechanic, he kept telling me he thought it was the fuel pump, but each time (3) he checked it, he couldn’t find any problems. One day I had to call him from the road to come an get me. So, when it works its good. So when it don’t work, its bad. Let your mechanic drive it a few days, he might can find the problem. The amount of fuel in the tank when this happens, probably has nothing to do with the stalling, unless of course it is about out of fuel.

Buick Stalls When Gas Tank Is Less than Half Empty

The old double-negative, eh? Good thing you clarified in the post body because this would mean it stalls when it’s above the mid point…

Try the simple stuff first. As gas is consumed, the tank must vent to allow air in to replace the fuel. If it doesn’t, a vacuum condition will occur and the pump can be starved. When it stalls, act quickly (but safely) to remove the gas cap and note whether or not there is a big whoosh as air is sucked into the tank.

For that matter, the next time its at a point where this might happen just try driving around without the gas cap for a while and see what happens. This might turn on the check engine light but at least you’ll be able to find out if venting is a problem. If it isn’t venting then I’d be suspecting the fuel pump. The pressure needs to be tested under load, not just sitting at idle.

As gas is pumped out of the tank, the tank breaths air in through an “activated charcoal bed” in your charcoal canister to fill the space. If the “bed” becomes saturated or the line to it becomes kinked or plugged, such that the tank has difficulty breathing in, a vacuum can develop in the airspace that can prevent the pump from being able to pump out gas sufficiently to maintain pressure.

Your charcoal bed may be saturated or your line kinked. Do you “top off” when you fill with gas? In some vehicles that can saturate the bed.

The next time this happens, try removing the gas cap and reinstalling it. If you hear a “whoosh” of air rushing into the tank and the problem goes away, look to the EVAP system for a permanent fix.