Last Updated on September 24, 2021
Gasoline and diesel automobile engines are dependent on a moderately complex fuel delivery system. This system brings fuel to the engine at the precise flow and pressure to enable proper operation.
For most modern cars, one or more fuel pumps are the heart of this arrangement. 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.
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.
A Real World Example Fuel Pump Failure
Fuel pump performance problems can occur intermittently. But trouble can be followed by periods of perfect serendipity. It’s just life.
Imagine driving to work on the freeway and your trusty car suddenly loses power and comes coasting to a stop. Not only embarrassing, this event can put you in danger just getting over to the breakdown lane.
So, you try to start it, and it fires right up. Yayyy! You pull back into traffic. Everything seems fine until the same failure occurs minutes, hours or even days later. Your once reliable friend becomes an inconstant monster now willing to let you down on a moment’s notice.
An intermittent problem like this can pester you repeatedly until the ailing pump gives up completely perhaps leaving you stranded.
Why Fuel Pumps Fail
What causes lie in wait to ambush you with this kind of problem? Here are some common ones:
Late model automotive pumps are complex and may include pressure control and/or relief valves. Failure of these features can reduce output pressure or recirculate fuel back into the tank leaving none for the engine.
Contamination with sludge from that backcountry service station fill-up last week can gum up a pump or block its inlet screen. Reduced or zero flow will result.
Clogged Fuel Filter
If not replaced at normal service intervals, a fuel filter can become clogged with silt or even water. This can restrict fuel flow and cause pump failure symptoms. Reduced flow can also cause a pump to overheat resulting in permanent pump damage.
Damaged Fuel Line(s)
A tire-launched pebble can dent one or more fuel lines pinching fuel flow thus mimicking fuel pump failure.
Things simply wear out with age. Age degradation can bring any pump to its knees though such would not be expected until well beyond 100,000 miles.
An Early Warning from Your Instrument Panel
With fuel system problems, your instrument panel can be your silent but capable partner. It can provide you with an early warning of looming fuel system problems before you get stranded.
How, you ask? Have you ever noticed that yellow “Check Engine/Service Engine Soon” light? It blinks on and then off when you start the engine. Look for it next time you hop in the car.
Your owner’s manual will show you what this light looks like and where it’s located. All cars 1997 or newer will have this warning feature.
How the Onboard Diagnostic System Works
This light is going to come on when the onboard diagnostic (OBD) system detects any one of several emission system problems.
The fuel system problems it will note include repeated engine misfires and/or abnormal variations in fuel pressure. These can happen when the fuel pump begins to struggle.
And this warning will often occur well before severe running problems leave you stalled alongside the road.
A Warning that Should be Heeded
Never ignore this warning light. Indeed, continued operation of your car with this light glowing can result in engine or related system damage that could be extremely costly to correct.
When this light comes on, you should always seek professional help. Soon!
Diagnostic Fault Codes: How They Help You
This light provides a warning, but it signifies much more. With this alert, the onboard diagnostic system gets busy and stores one or more diagnostic fault codes (DTC). These codes can be interpreted to tell you the nature of the problem.
A local auto parts store can generally evaluate the stored codes for you at no cost using a special tool called an OBD-II scanner. If you’re serious about doing you’re own automotive repair or maintenance, this automotive scan tool will usually pay for itself after a few uses.
However, while knowing what fault codes were triggered is helpful, it often proves far more beneficial to take your car or truck to a competent service technician. Such folks can provide accurate diagnosis as well as any needed repairs.
At the Repair Shop
Now the hard part. If your technician finds the fuel pump to be the cause of your fuel system problem, replacement could be costly. Additionally, the replacement pump may have to be ordered. Your favorite ride may have to sit at the shop awaiting that part.
In this case, most dealers will offer you a loaner car for use until yours is fixed. Or at the least they will offer to give you a ride home if you are stranded.
This benefit is not so common among independent repair shops. Should they have a pump in stock or can get one quickly, replacement usually takes no more than two to three hours.
Fuel Pump Replacement Cost
Let’s look at costs. A typical fuel pump replacement will require $120 to $240 for labor. Parts cost will be added to this. Depending on your year, make and model, a new pump price can range from as little as $100 to $1200 or more.
Late model cars will have far more costly pumps than, say, a 15 year old rig. Other parts like new clamps, fittings and interconnect hoses may also be needed. Include $50 to $75 for these.
The total could run from as little as $270 to over $1500. Any sales tax will increase your final bottom line. To save a bit of money, opt for a good independent repair shop instead of the dealership and consider an aftermarket pump versus what may be a costlier OEM (original equipment manufacturer) unit. But in most cases, it’s recommended to go with an OEM pump.
As already mentioned, both parts and labor pricing will generally be higher at a dealer service department than with an independent shop. But with a dealer you will likely get a better warranty than a private shop can offer.
Last, if you are going after competitive repair estimates, be sure to ask about this warranty. And when you return to pick up your car, do make sure you have that warranty in writing.
You are heading back home with a bit of a smile. The car is running perfectly. What can you expect down the road? As when the car was new, you should be able to look forward to another 100,000 miles with no fuel pump problems. Happy Motoring.