Why running your tank low can be a very bad thing

So we’ve done our second fuel pump in as many weeks. Both vehicles belong to driver’s who frequently play chicken with the gas light. 

Let’s start with what a fuel pump does. It’s pretty simple, the fuel pump is responsible for delivering fuel from the tank through the fuel filter and then into the fuel rail which feeds the fuel injectors. Any excess (or unused) fuel is then collected by the fuel pressure regulator then returned back to the fuel tank. 

The fuel pump lives in the fuel tank. Like any electric pump, it generates heat while operating. The fuel in your tank is not only responsible for powering your engine, but it also helps keep the pump cool. A cool fuel pump is a happy fuel pump. If you are the kind of person who fills their tank 5 gallons at a time, your fuel pump never has the opportunity to be submerged and run at cooler temperatures. The pump will always run hot which creates a high stress environment and will cause premature failure.

Fuel pumps typically range in price from $150-$500 and with an average labor cost of $300-$500 to replace. Bet that extra $40 to fill your tank seems a little more appealing? Because changing the fuel pump is a very labor intensive job, we prefer to use the OEM (Original Equipment Manufacturer) brand pump for the vehicle. There are less expensive options available but our experience has shown us that those pumps are more likely to fail within a shorter period of time. The savings negates the worth of having to tow the vehicle in when the pump fails again and having to do the job a second time.

There is also a fuel level sensor that lives in your fuel tank. The sensor is usually connected to a “float” (similar in concept to the ball float in your toilet tank). The float moves up and down with the fuel level and relays that information through the sensor to the fuel gauge on your dashboard. If the fuel level never changes, the sensor will wear heavily in that one spot and can lead to failure. Conversely, this is also a common problem seen also in vehicles where the owner always keeps the tank full. This will leave you guessing on whether or not you’ll be able to make it to your destination.

You always hear us stressing the importance of tracking your miles per gallon. Well this is yet another reason why that’s important. If you know you average 350 miles per tank, in the event the level sensor fails, you’ll be able to estimate how many miles you can drive on a fill-up until you are able to get the sensor repaired.

We’ve all heard of “dry gas” and some of us have had to use it. Well dry gas is used when water is introduced to your fuel tank. If the tank spends most of its time mostly empty, water will begin to collect inside the tank, especially if it’s colder out. Keep in mind, your fuel system is not sealed. There are vent valves and hoses that allow fuel to displace the air in the tank when you are filling it. Just as it is designed to allow air escape, it just as easily allows air in. With the introduction of Ethanol blended gasoline, water condensation is a more common problem. Ethanol is a type of alcohol and alcohol “attracts” the water in the air. This is the primary reason why you should always fill your tank during the very cold months or expected winter storms. The second reason of course being the potential of power outages and limited access to fuel. 

Water in your gas will cause either a poor running or no start condition. Long term exposure to water in your gas can also lead to rust conditions if you have a metal tank. Rust can lead to debris in the tank which will clog the fuel filter and/or fuel lines possible even the fuel injectors, causing very poor running conditions or no start conditions. It can also lead to the tank itself rotting which is very unsafe. 

It is important to change your fuel filter at regularly scheduled intervals. This will help keep the system running properly as well as prevent debris from entering the system and possibly entering the fuel pump and causing the pump to prematurely fail. 

If you have any questions about any of the topics discussed or are concerned about the conditions of your fuel system, please send us an email Bill@BMARauto.com and we will be more than happy to help!