Low fuel level: running on empty

Dear Car Talk

Dear Car Talk | Sep 01, 1990

Dear Tom and Ray:

I have a 1988 Chevy pickup. Last week I had the gas tank down more than it had ever been. It indicated 1/8 tank. While starting from a stop with the truck facing slightly downhill, the engine stalled. Did the the gas tank cause this? The truck has 25,000 miles and has always run perfectly. I'm getting a new gas filter today. Any other suggestions?

TOM: I know quite a bit about running a gas tank down to near empty, Russ. I have a '74 Chevy which I'm afraid could die at any moment. Being a cheapskate, I keep the tank near empty so it won't get towed off to the boneyard with $15 worth of perfectly good unleaded still in it.

RAY: Actually Russ, there are two things associated with low fuel level that could cause your truck to stall. The first has to do with pointing down hill. The fuel pickup does not reach all the way to the bottom of the tank. So if the truck tilts...

TOM: Tilts? What is this, a truck or a pin ball game?

RAY: Ignore him, please. If the truck tilts, there may be gas in the tank, but it may be out of reach of the fuel pickup.

TOM: This is easy to demonstrate at home. Take a glass, and fill it 1/8 of the way up with water. Then take a straw, and put it right in the center of the glass so that it's barely submerged in water. Now tilt the glass. You see what happens? There's water in the glass, but the straw can't reach it. That could be what happened in your gas tank.

RAY: The other possibility is that there's water at the bottom of your tank. Condensation builds up over time and sinks to the bottom. So you may have been sucking up water in addition to or instead of gas.

TOM: You may also have picked up rust or other dirt lurking at the bottom of the tank, so changing the fuel filter is a good idea. I'd also add a family size bottle of gas line anti-freeze (which eliminates moisture). And until your car is as old as mine, Russ, keep the tank at least 1/4 full.

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