The fuel pump is the heart of the fuel injection system. Without it, fuel won’t leave the tank, and your engine won’t run. Although it’s by no means a regular occurrence, fuel pump failure is not unusual in older vehicles. Unfortunately, it’s not always the easiest part to replace. The good news is there are usually a few signs alerting you to impending failure, so you can fix the problem before you’re stranded.
Heart of Gas
The fuel pump is often (but not always) located inside the fuel tank itself, and attaches to a float and electrical connections that update you on how much fuel is left in the tank. It sucks up fuel and sends it through lines to the injectors, which meter out the proper quantity for combustion. The pump must meet manufacturer specifications for fuel volume. If it fails to meet these standards, you run into all sorts of problems starting and driving.
Pump and Circumstance
Note that most of these symptoms on their own might have other causes, but if you see one or more together, go to a mechanic for a conclusive diagnosis.
If the fuel pressure is low, you might have trouble starting your car — it may crank longer than normal before firing up, or you might have to cycle the key on and off several times to prime the necessary pressure. Once it runs, you might get a rough idle or stuttering while driving up hills or upon acceleration. It’s possible it could stall out completely, or it might just result in a noticeable misfire.
You may find that your engine temperature is higher than usual, as it struggles to keep up with uneven fuel supply. Occasionally, a failing pump will cause an engine to surge, because it’s no longer capable of consistent volume. You might even hear the fuel pump itself struggling, which sounds like a whining or loud buzzing noise coming from the tank. The last clue might be at the gas station: Pumps on their way out reduce efficiency, which means your mpg will suffer, and you’ll have to stop to fill up more often.
To diagnose a bad fuel pump, you’ll need a special tool for pressure testing. This connects to a designated valve on the fuel line, and will show you what the PSI in the system is when the engine is on. There are other reasons the PSI might be off (such as an obstruction or a leak), but a good mechanic will be able to put all of the symptoms and data together to condemn the pump definitively.
Now for the tricky part — a few vehicle models have external or easy-to-access pumps, but a great many pumps are located inside the tank … which means the tank has to come down to change it. It’s a headache, especially if you’ve already got a lot of fuel in there weighing things down. Unless you have the know-how and a garage full of the right equipment, this is one task that’s best left to the professionals at your local NAPA AutoCare.
When changing a fuel pump, choose a good replacement. It doesn’t have to be made by the manufacturer, but it sure better match the specs and be from a trusted brand, or you’ll find yourself back in the same predicament in a few years.
Check out all the fuel & emission system parts
Photos courtesy of Blair Lampe.
Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter. In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck.