Low on gas = odd symptoms
 

When my car is low on gas, it will sometimes stall immediately after starting it if the engine is warm. Also, when I bump start it after EOC it will lag for responding to the gas pedal. This only happens when it's low on gas.. Any ideas? I think the onset of the problem may have coincided with my muffler going bad (it's rusted out). Do you think there is any reason to think the two could be related?

Car is a 1993 Honda Civic VX.

This is common for older fuel injected vehicles. My dad once had a Chevy Lumina van that was almost undriveable under 1/8 of a tank. Apparently carbureators were very forgiving about not having a constant fuel flow, as the engine would run on fuel in the carbureator bowl, even if the fuel sloshed away from the fuel pickup in the tank. Fuel injection is very different. That's why a proper fuel injection conversion on older vehicles requires replacing the fuel tank with an anti-slosh tank, otherwise you really can't drive it well under 1/4 tank.

-Jay

Yeah air in the fuel lines causes problems - if your fuel system circulates fuel from the tank to a pressure regulator and bleeds the excess back to the tank then the air gets purged but if it only flows to the engine (like my xB) then the air has to pass through the injectors and it only takes a little bit of air to cause misfires.

My civic is the same way when it gets low. As soon as I fill up, it goes away. The easiest answer is to never run it that low. ;) Beyond that, try this trick:

Do a very quick key off-on, then wait about 5 seconds. Do it again, for up to five cycles. Each time builds more fuel pressure. Once the pressure is up, it'll start just fine. If you do this while sitting still, you should be able to hear the fuel pump change to a different sound when the pressure is good.

I have had 6 cars ranging from 16,000 miles to 280,000 miles. I typically run my cars until the fuel light is on (if it has one) before refilling it. I have noticed that the Hondas (all 5 of them) take longer to start when the fuel is under 1/4 tank. Otherwise, all of mine have driven just the same. I have run out of gas once in my '88 Accord and once in my '95 VX. Both quit with no sputtering or warning. They ran normally until they shut off. My Accord had a 2 bbl carburetor. The VX has FI, of course.

My theory is that since I run them low on fuel so often, I do not get an accumulation of junk in the bottom of the gas tank. I also only run FI cleaner every 30,000 miles or so. I notice no performance or FI gains, so I can only assume that either the stuff does not work, or else the car's fuel system is clean enough to begin with. I change fuel filters every 50,000 miles or so.

It's probably a good feature in my case as it gives me more incentive to fill up and thus reduce the risk I'll run out of gas since I have a tendency to wait till it's too late. Is it bad for the engine to let it lag like that? I'm guessing it's probably not a big deal.

Most fuel injection pumps are cooled by the gasoline they are pumping- so if they run out of gas, the pump will be spinning and heating up- possibly decreasing its lifespan.

Several things happen when you get low on fuel, it sucks air from the tank, the gas moves around sometimes away from the pickup, stopping and starting move the fuel around away from the pickup, parking or stopping on an incline moves the fuel around and can make it hard starting. Best not to run low as the pump is cooled by the fuel and surges in the fuel lines can hammer dirt in the lines loose and perforate the fuel filter.

You realize how ridiculous it would be to constantly keep the tank filled to the point where it submerges the fuel pump? Some cars have HUGE tanks, like hortizontally but shorter vertically, so you'd have to keep the tank 3/4 filled in order for it to TOUCH the fuel pump. I see this all the time and I personally think it's a bunch of nonsense.. It's an electric motor, it doesn't HAVE TO BE SUBMERGED. Unless this motor is at the very bottom of a small tank (horizontally), I'd say you're perfectly fine running it on empty.

Erik's right. Most fuel pumps are cooled by the gasoline. Keeping it above 1/4 tank should ensure normal service life. Running it down to fumes all the time risks premature failure.

I had a fuel pump fail around 120,000 or 140,000 on my truck, blamed on my habit of running it down to fumes every tank.