10 Symptoms of a Bad Fuel Pump
For most modern cars, one or more fuel pumps are the heart of their moderately complex fuel delivery system. When one of these pumps fails to perform properly, your morning drive to work may suddenly be interrupted.
Fortunately, there are certain signs of a bad fuel pump that you can look for when troubleshooting the issue. But if the pump needs replacement, you may be a bit shocked at the replacement cost.
How a Fuel Pump Works
How does this fuel delivery system operate? In principle it’s quite simple. From your car’s fuel tank, metal piping conveys fuel to the engine.
An electric fuel pump, generally located inside the tank, clicks on when you start the engine and the vehicle’s ECM instructs the fuel pump relay to turn it on. You may hear its tell-tale whirring sound. The pump pressurizes the fuel and pushes it through the piping.
Under the hood, a second electric or engine-driven mechanical pump is used in many cars to boost fuel pressure. At high pressure, the fuel will be sprayed into the engine through precisely timed fuel ports called fuel injectors. This arrangement is very reliable. When it’s working well, your engine will start quickly and run with remarkable enthusiasm.
Fuel Pumps Can Fail
But it’s not a perfect world. Stuff happens. And occasionally it happens to your fuel delivery system. One troublesome event with this system can be the fuel pump failing to either pump sufficient fuel or any fuel at all.
With insufficient fuel your engine will run very poorly. When no fuel is supplied, your engine will suddenly stop and will not restart until pumping is restored.
Bad Fuel Pump Symptoms
Often before the fuel pump quits completely, behavioral symptoms begin to tell you something is not quite right. Your car may exhibit one or more of these if your vehicle’s fuel pump is on its way out or has already failed.
1) Difficulty Starting (or Can’t Start at All)
This is that grim moment when you turn the key (or push the button) and little or nothing happens. Cranking the engine can take longer than normal. Sometimes way longer. And a failure to start at all will be painfully obvious.
2) Sudden Engine Stalls
As if without cause, your engine will stop running. At most any time. This can be a simple annoyance if idling in your driveway or downright dangerous if it happens on the road. A description of just such an event is provided below (skip to: “A Real World Example of Fuel Pump Failure“).
3) Rough Running at Idle and Low Speed
Rough running as a one time event is generally not an issue. But if this recurs frequently, take notice. Fuel pump problems may be the cause.
4) Engine Misfires
Misfires will be felt more than heard. A series of misfires will feel like the car is bumping through a bunch of large soft pillows. Because misfires can eventually damage your engine, correcting the related fuel pump problem as soon as possible is very important.
5) Hesitant Acceleration
Typically your car will quickly accelerate from a full stop. This instant response is important when turning onto a busy street or merging into traffic on the highway from an onramp. Delayed or pokey response when you step on the gas can occur when the fuel pump is failing.
6) Engine Speed Variations While Driving at a Steady Speed
Ups and downs in fuel flow can cause surges in power. The car will want to accelerate, slow down, and then repeat this cycle. This behavior can be risky on a crowded highway.
7) Reduced Power
With an insufficient supply of fuel, you may notice a reduction in power. At times, this can mean you lose the ability to reach and maintain highway speeds making your vehicle a moving obstacle. If this happens, turn on your flashers and get off that busy road ASAP. Stop and call for help.
8) Poor Performance When Climbing a Hill
We do not live in a flat world. Most of us anyway. Hills abound, and meeting a hill or other incline your car can’t climb is just another indication the fuel system is calling it quits.
9) Increased Fuel Consumption
A failing fuel pump can affect your engine by increasing fuel consumption. Should you notice this with no other unusual symptoms, having your fuel system checked by a qualified service technician is strongly advised.
10) Check Engine Light Comes On
The glowing Check Engine Light can tell you you have a fuel pump problem. An in-depth discussion of onboard diagnostics and this indication of fuel pump failure is provided below.
In general, when the fuel pump is off its game, your car may act a bit herky-jerky. It will feel unwilling to run with any of that old enthusiasm you loved so much. Such ill behavior will be instantly noticeable to most drivers.