78(8 Fuel Pump System Malfunction

The fuel pump is an integral element of any car. Given the responsibility of literally pumping a vehicle’s fuel from its tank to the engine, a malfunctioning fuel pump will always lead to total disaster. Therefore, drivers need to be aware of the common symptoms of a malfunctioning fuel pump so as to address the problem before it leads to a car or truck that won’t start.

This guide is designed to explain the 5 most common signs of a failing fuel pump in an effort to educate drivers. That process begins with an explanation of the role and function of the fuel pump itself, which will help vehicle owners to understand the reasons behind fuel pump malfunction. Next, 5 common symptoms of a malfunctioning fuel pump, including everything from engine misfires to cars that won’t start, will be described. By the end of this guide, car and truck owners will understand what symptoms to look for in their own vehicles so that they can catch a fuel pump malfunction before it leads to total vehicle failure.

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  1. Use Figure 1 below as a reference for the orientation and location of the fuel system components. Failure to do so will result in a system malfunction.
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All About Fuel Pumps

The fuel pump is an essential component of any vehicle with an internal combustion engine, principally, cars and trucks. With the job of forcing fuel from the gas tank towards the engine, a malfunctioning fuel pump will create a situation where the engine either gets too much or too little fuel due to too much or too little pressure in the line traveling from the tank to the engine. This will lead to performance issues with the car or truck itself.

In the most basic sense, in order for an engine to run properly, fuel in the form of liquid gasoline needs to travel from the tank where it is stored to the engine where it is burned to create power and propel the vehicle. Some smaller, more concisely constructed vehicles, such as certain models of motorcycles, do not require a fuel pump because gravity takes care of this job. However, this is not the case for most internal combustion engine vehicles. Instead, they utilize either a mechanical or electronic fuel pump.

The Mechanical Fuel Pump

Traditionally, all fuel pumps were always mechanical. This means that they operate through a system that runs off of the rotation of the engine itself. A mechanical fuel pump resembles a diaphragm. It uses the pumping action of that diaphragm shape to create low pressure (10 to 15 psi) and transport fuel from the gas tank to the carburettor… This action resembled that of a piston.

Mechanical fuel pumps are located on a mount outside of the fuel tank itself and, in general, are less likely to malfunction than electronic fuel pumps. The most common malfunction of mechanical fuel pumps comes when the diaphragm inside the pump splits, disturbing the pressure balance of the pump. The other cause for mechanical fuel pump malfunction is high heat created from both the engine and the air outside turning the fuel to vapour. This prevents the pump from operating since it is designed to handle liquid only.

The Electronic Fuel Pump

Though the mechanical fuel pumping system was always sufficient for carburettor-based fuel systems, eventually vehicle manufacturers moved past the use of carburettors in favour of a more advanced fuel injection system… Though the fuel pump itself is still necessary, the mechanical pump cannot generate the level of pressure needed to work with fuel injection engines. Therefore, a new system which delivers fuel under high pressure (40 to 60 psi) was created. This system is what is known as an electronic fuel pump.

Nowadays, most vehicles use an electronic fuel pump, which is located within the gas tank itself, to deliver fuel to the engine. However, there are far more inherent issues with electronic fuel pumps. The electronic system works by spraying a fine mist of fuel inside the engine’s chambers and is operated through a computer control system rather than a mechanical one. As a result, both issues with the pump itself as well as the computer used to operate it can lead to vehicle and fuel pump malfunction.

After understanding the function of a fuel pump itself as well as the important differences between mechanical and electronic fuel pumps, understanding the common symptoms of problems with this component will make more sense. Remember, the purpose of a fuel pump is twofold:

  1. It pushes (or pumps) fuel from the gas tank to the fuel injector or carburettor.
  2. It creates the proper amount of pressure (low or high) to ensure that the right amount of fuel will be delivered to the engine, regardless of external conditions.

Therefore, malfunctions in the fuel pump can result from an issue in either one of these processes. Let’s take a look at the common signs of these problems.

1. The Engine Sputters at High Speed

The most common early sign of a problem with a fuel pump comes when driving a vehicle at a consistent high speed. While traveling down the road, the car will run well for about 10 miles and then begin to jerk around, or sputter, for a mile or two before returning to normal.

What This Means

Many people will mistakenly diagnose a sputtering vehicle as one with “dirty” gas or some other fuel-related issue. And while that can be the case, it is not uncommon for a fatigued fuel pump to create this same symptom as it struggles to supply a constant stream of fuel to the engine at the proper pressure. The loss of pressure causes the engine to sputter.

2. Vehicle Loses Power While Accelerating

The feelings generated by this second symptom are very similar to the first. However, rather than experience a sputtering sensation while driving, vehicles will experience it upon acceleration from a stop. Generally, the vehicle will initially move before making noises and jerking around as if it will stall. Then, it will continue on its acceleration path smoothly.

What This Means

The process of acceleration creates an increased demand for fuel by the engine. A malfunctioning fuel pump, again, cannot maintain the required pressure to deliver this fuel in a steady manner, thereby causing the engine to improperly mix fuel and air and lose power. Once pressure is restored, the engine is able to run smoothly and the car takes off.

3. Sudden Loss of Power When the Vehicle Is Under Stress

A car or truck is put under stress when the work needed to complete an ordinary task, such as forward movement, is somehow hindered by external forces. Generally, this occurs when climbing a hill or when hauling a load. If, when completing these tasks, the vehicle loses power, cannot accelerate, or begins to sputter, the fuel pump is a possible culprit.

What This Means

Generally, a fuel pump, even an aging one, can maintain a steady stream of fuel and pressure when operating under normal conditions. However, once put under stress, the weakening elements of the pump will begin to take control and the fuel delivery will not be able to keep up with its demands, leading to power loss.

4. Surging

The opposite effect of the above symptoms, surging, can also be a sign of a malfunctioning fuel pump. A car that surges will be moving along normally at a consistent speed. Then, with no driver intervention, will pick up and “surge” forward, as if the gas pedal had been depressed.

What This Means

This is something that many people will mistakenly blame on the fuel filter since it is not “like” any of the other fuel pump malfunction signs. However, this surge is created because, as a result of age and normal wear and tear, the fuel pump now has irregular resistance within its motor. This creates a situation where the pump cannot draw enough electricity to maintain the pressure needed for steady speeds and may “surge” with a sudden ratcheting up in pressure.

5. The Engine Will Not Start

The final symptom of a malfunctioning fuel pump is also the most severe. Drivers who ignore the signs listed above will all eventually end up here. When a car or truck’s engine will not start as a result of a fuel pump malfunction. Basically, the engine will rev, but it will not catch.

What This Means

When a fuel pump has malfunctioned to the point that the car will no longer start, this means that there is no fuel reaching the engine upon ignition. For that reason, drivers will hear the sparks try to ignite, but there will be no fuel to burn. To diagnose a fuel pump malfunction, check for a blown fuse and pressure in the fuel line (it will be 0).

Conclusion

As an essential element of any internal combustion engine system, the fuel pump is one of those automotive issues all drivers need to keep in mind. Like any aspect of vehicle operation, understanding what a fuel pump does and the different ways that it can fail can help drivers avoid bad situations with a failing car or truck. With the important tasks of delivering fuel to the engine as well as maintaining a consistent stream of pressure while doing so, a malfunctioning fuel pump will present in several ways.

The 5 most common symptoms of a malfunctioning fuel pump include sputtering at high speeds, loss of power during acceleration, loss of power to the vehicle while under stress, surging, and, finally, an engine that will not start. Understanding these symptoms and correctly identifying them early is the only way that drivers can avoid getting to the point where their vehicle will not start, stranding them and costing a lot of money in repairs.

78(8

The fuel pump is an important component of your vehicle. Without it, your car would die imminently

In all modern gas and diesel vehicles, a fuel pump is necessary, whereas, in older vehicles, the function depends solely on gravity to deliver the fuel.

A fuel pump can be damaged or fail for various reasons, such as the consistent use of contaminated fuel or poor quality fuel.

In this article, you will learn the most common symptoms of a poor fuel pump, location, and replacement cost.

Malfunction

8 Symptoms of a Bad Fuel Pump

  1. Car Experiences hiccups
  2. Misfires
  3. Sudden Engine Shutdown or no starting condition
  4. Backfires
  5. Check Engine Light Illuminates
  6. Thick black or white smoke from the exhaust
  7. Turbocharger Underperforms
  8. Spark Plugs Will Die Sooner

Because of the importance of the fuel pump, many things could happen if your fuel pump fails.

Here is a more detailed list of the 8 most common symptoms of a bad fuel pump.

Car Experiences Hiccups

Cars need fuel to drive, just as we humans need food. It is easy to understand how important fuel is, and it is also easy to see that your car will not meet your expectations if the correct fuel supply is not guaranteed.

If you press the accelerator and feel that your car has hiccups, you may have problems with the fuel pump.

The fuel pump may be choking due to inferior fuel, or the fuel pump may not be generating enough pressure to push the fuel forward into the system.

78(8 Fuel Pump System Malfunction

RELATED: Symptoms of a Bad Fuel Pump Relay & Location

Misfires

An insufficient supply of fuel to the combustion chamber will not create enough chamber excitement to cause an explosion. No combustion means that the engine will not start at all. Even if it does, you will find that it takes you a long time to reach ignition.

If you experience that your car has misfires or sounds like a tractor at idle, you might have low fuel pressure due to the fuel pump.

Sudden Engine Shutdown or no starting condition

The engine needs fuel to run, and if the fuel pump is bad, the engine won’t get any fuel. If your engine doesn’t start at all or having sudden engine shutdowns while driving, there might be a problem with the fuel pump.

If this occurs regularly, it is time to arrange a meeting with your local mechanic.

Backfires

Since a bad fuel pump can give an intermittent amount of fuel to the engine, you can experience misfires because of the too low fuel amount.

The engine can also get too much fuel, resulting in unburned fuel in the exhaust pipe, which will cause backfires from the exhaust pipe.

Check Engine Light Illuminates

Fortunately, modern cars are loaded with sensors that can detect any number of problems as soon as they occur. One of these sensors is a fuel pressure sensor that is intelligently measuring the fuel pressure. If an irregularity is detected, the sensor sends a signal to the ECU, which lights up the check engine light.

You can easily check the error code displayed by the Check Engine Light through an OBD2 Scanner.

Thick Black or white Smoke from Exhaust

Vehicles do not normally emit black smoke from their exhaust unless they are powered by diesel fuel. If your gasoline-powered car emits such smoke, there is usually engine damage.

One of the causes of black or white smoke is a defective fuel pump, making your engine get a rich fuel mixture. In most cases, a bad fuel pump is giving a lean mixture, so this is not a very common one.

Turbocharger Underperforms

First of all, not all cars have a turbocharger, but those with one have a bonus symptom. Turbochargers work by compressing airs to rotate a turbine that delivers additional power to the engine.

Turbos need time to spool air; this time is usually called turbo lag. So if you feel that there is a lot of turbo lag, your fuel pump could be a problem.

Spark Plugs Will Die Sooner

Fuel does actually cool down internal engine parts. With a too lean air-fuel mixture, you can actually make your spark plugs getting too hot. A defective fuel pump interferes with the internal workings of the engine.

The smallest damage occurs in the cylinder itself, and the smallest components take the greatest damage. This means the spark plugs may die before their time.

So if you feel that your spark plugs need to be replaced too soon, you may be dealing with a faulty fuel pump.

What is a Fuel Pump?

The fuel pump’s main function is to deliver fuel to the fuel injectors, injecting fuel into the combustion engine system. In most cases, carburetor engines use the function of mechanical fuel pumps, which are mounted outside the fuel tank and operate under low-pressure conditions.

78 8 Fuel Pump System Malfunction Short

Apart from carburetor engines, diesel engines often use two main pumps to deliver fuel, which works electrically and improves performance efficiency.

One pump is installed inside the fuel tank, which delivers more fuel at low pressure, while another pump is installed near or inside the engine, which sucks in the required amount of fuel at a higher pressure.

For the maximum efficiency and proper functioning, the fuel pump operates under certain conditions that are electronically adjusted to optimize the combustion engine’s air-fuel mixture. If more fuel is supplied to the engine, the air-fuel ratio is disturbed, and all the fuel cannot burn efficiently.

Fuel Pump Location

The fuel pump is almost always located at the top and inside the fuel tank on newer cars. Some cars have a cover to remove under the backseat or in the trunk to reach the fuel pump’s location.

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Unfortunately, you have to remove or lower the fuel tank to reach it for some cars.

Fuel Transfer Pump

Some older cars do also have an external fuel pump located outside of the tank.

Fuel Transfer Pump Harbor Freight

Fuel Pump Replacement Cost

The average fuel pump replacement cost is between $100 and $700, depending on the car model and labor costs. A fuel pump costs $50 to $400, and the labor cost is $50 to $300.

If you have a petrol engine with an electronic fuel pump, the fuel pump is often not very expensive. The expensive part is letting a mechanic replace the pump. The pump is often located inside the fuel tank, which means that there is a cover to reach it from under the back seat if you are lucky. But, there are car models you have to remove the whole fuel tank to reach it. You can imagine the time it takes.

In some cases, you can do it yourself if you have some experience, but remember it is a really nasty job and not good for your health.

If you have a diesel engine and want to replace the mechanical fuel pump, you can expect a much higher replacement cost. These pumps can cost up to $1500 if you are unlucky, and the replacement cost is often also very high. After this, you do often need an adjustment of these pumps also.