We Buy All Cars, Running or Not!

How To Test Your Fuel Pump – AND The Faulty Fuel Pump Warning Signs!

How Do I Know When My Fuel Pump Is Bad

The fuel pump in your car is a device that moves and transports fuel from your tank to the engine, supplying the amount of fuel at the right pressure to ensure that your engine runs smoothly and runs consistently. Depending on how old your vehicle is, you might have either a mechanical or electronic fuel pump. 

⚠️ If It's Broken, Don't Fix It - Get Paid Cash for Your Vehicle ⚠️


Mechanical fuel pumps run off of the motion of the engine, and feature a diaphragm attached to the outside of the fuel tank expands and contracts to create a low pressure system to force the fuel out of the tank and into the engine. The electronic fuel pumps are generally inside of the fuel tank and use electromagnetic motors to force fuel to the engine at high pressure. 


Since mechanical pumps are directly driven by motion and physical pressure, they tend to be reliable and relatively easy to diagnose and fix. Most problems with the mechanical pumps occur when the diaphragm is damaged, and throws the pressure system off balance. 


In order to know how to test the fuel pump, you should know the key signs of a failing fuel pump and how to diagnose a failing fuel pump in your car. If your car jerks or sputters at high speeds, you might be experiencing fuel pump failure since the car can’t deliver a smooth flow of fuel to the engine. In addition, your fuel pump could be damaged or not working correctly if you lose power when accelerating. 


Furthermore, your fuel pump could be damaged and you might need to learn how to test the fuel pump if you are losing power while driving uphill or towing a load. Also, your fuel pump could be damaged or having issues if your engine surges. Lastly, you need to learn how to test the fuel pump to see why your engine will not start. 


How to check and test your fuel pump 


In order to determine if you need to fix or replace your fuel pump, you need to know the proper step of checking and how to test the fuel pump. If you are struggling to accelerate properly in your car, especially when driving at high speeds on the highway, or you notice other signs that your car is not getting enough power or enough fuel in the lines, then the problem can most often be attributed to a partially blocked or clogged fuel line, blocked fuel filter, clogged fuel pump, or faulty fuel injector. If your car will not start at all when you are trying to accelerate or drive, there are a few tests you can figure out to run. Here we can figure out the steps of how to test the fuel pump.

Performing an electrical test


One of the main methods that you can use in how to test a fuel pump is using an electrical test. The first step is to check the fuel pump fuse, since more often than not it is not the pump that fails, but the power that supplies it. Find the location of the fuse box and then find the correct fuse that matches with the fuel pump. Pull out the fuel pump and check for any signs of failure or if the fuse is blown. 


If the fuse looks good and does not show any damage, then you do not need to replace them. When this is the case, have a helper turn the key while you listen to the fuel pump relay clicking on. If you do need to replace a fuse, make sure that you use one with the right amp rating. 


The second step in performing an electrical test is to check the voltage at the pump itself. Just because you are getting some power from the circuit does not mean it is actually traveling directly to the pump, which makes it important to check the voltage in two places. 


The third step is to perform a drop test with a voltmeter. Make sure the power wire shows that there is full voltage and the grounding wire is positioned correctly. If the electrical test shows no issues, then it is likely that your fuel pump is the issue and needs to be replaced. That is the last step in performing an electrical test when using a method of how to test the fuel pump. 

Performing a fuel pressure test


The first step of performing a fuel pressure test is to eliminate the filter as the reason for the fuel issues. If the filter is clogged with debris and dirt, you can have trouble accelerating and might think that your fuel pump has an issue. To check the filter, you need to remove it and drain excessive fuel. Use a short piece of rubber hose on the filter inlet and inspect the screen for debris and replace the filter if necessary. 


The second step would be to use a fuel pressure gauge in the fuel pressure test and hook the gauge to the fuel pump test fitting. Locate the fuel pump test point and find the point at which the pump hooks up with the filter injector rail. Then, have another person rev the engine while you check the reading on the gauge. Let the engine warm up slightly and then check the pressure at idle speed and the speed in the pump specifications. 


Checking the fuel pressure or volume in your car can tell you whether or not enough fuel is going from the tank to the engine. Whoever, this doesn’t necessarily mean exactly that the pump is bad when you are learning how to test the fuel pump. You should check the fuel pressure by using mechanical fuel pressure gauges.  


After you check the fuel pressure using the mechanical pressure gauge, you need to perform a static fuel pressure test and connect the gauge as outlined in your repair manual. Then, turn the ignition to the on position and note the reading on the gauge and compare it to specification in your manual. 


When you are performing the static test, you will need to note what the pressure holds. The factory repair information will tell you how long the pressure should hold once the pump is turned off when learning how to test the fuel pump. 

If the problem is fuel-related


One of the steps in how to test the fuel pump is to verify if the problem is directly related to the fuel. After you have determined the source of the issue, you can then do additional testing to find out if the pump is really the culprit to blame. If you find that the engine will not start, you need to listen for the fuel pump. Put your ear near the fuel tank and turn the ignition to the “on” position. 


If the engine will not start, then you need to whack the fuel tank. Have a helper crank the engine and then hit the fuel tank with a mallet, seeing if the vehicle is able to start during this procedure or if the fuel pump is bad. 


In addition, if the engine will not start, then you might have to use starter fluid to see if the engine will then turn on to see how to test the fuel pump. If you try to do this test, attempt starting the vehicle by removing the air intake and spraying starter fluid into the throttle body. 

Fuel pump warning signs


As we know, the job of the fuel pump is pretty self explanatory but also very important. The job is to pump fuel from the gas tank to the engine to power the car. It is pretty self explanatory that the malfunctioning fuel pump in your car could be very bad news – that is why we told you how to test the fuel pump. In addition, it is important to familiarize yourself with the warning signs of a  faulty or damaged fuel pump so you can fix any issues before it is too late. 

Engine sputters at high speeds


One of the best indicators and the main issues of a failing fuel pump is that your engine sputters and vibrates at high speeds while driving quickly. If the vehicle suddenly sputters and then stars performing regularly, then there could be something wrong with the fuel pump. This engine sputtering and vibrations happen when the pump is struggling to supply a constant stream of fuel to the engine at the right pressure. 


Other reasons for the engine sputtering at high speeds include faulty spark plugs, dirty fuel injectors, vacuum leaks, dirty mass airflow sensor, exhaust system leaks, faulty catalytic converters, dirty oxygen sensors, and worn out seals and gaskets. However, if you find that none of these problems is the issue, then you should learn how to test the fuel pump. 

Rising temperature


The temperature of the car can predict a problem with the fuel pump, so make sure you pay attention to the temperature gauge. If the heat rises and the car engine stalls, then this can mean the fuel pump motor is having issues working. If the car continues to stall and the engine does not work correctly, this is a clear sign that the fuel pump might be starting to deteriorate and the fuel pump is damaged. 


Other causes of the engine overheating and the rising temperatures in your car are that there is a leak in the cooling system, there is a condensed coolant, there is blockage to coolant circulation, there is a low level of oil, and there is a broken down water pump. If none of these problems cause the rising temperature, then you need to learn how to test the fuel pump. 

Fuel pressure gauge


The fuel pressure gauge shows how much fuel is getting to the engine, so you should check the gauge while someone else is in charge of revving and turning over the car. If your pressure is less than what is listed in the manual, then this means you need to fix the problem in your fuel pump and learn how to test the fuel pump.

Loss of power


When your car is put under stress, you can experience a loss of power. Stressful car situations involve the car going uphill, the car accelerating, and the car towing heavy cargo. In these situations, the weakening elements of the fuel pump can cause trouble and the pump can’t keep up with the demands of the vehicle’s fuel requirements, leading to a loss of overall power. 


There are also many other reasons why your car can lose power while accelerating. There can be low compression, a clogged fuel filter, a bad air filter, a clogged exhaust pipe, camshaft position sensor malfunction, mass air flow sensor malfunction, oxygen sensor malfunction, bad fuel injectors, bad fuel pump, or weak fuel pump. If these are not the reason, then you need to check out how to test the fuel pump. 



Engine surging can be a sure sign that there is a problem with the engine. Sometimes a car will be able to move normally at a constant speed, and then it will pick up and surge forward. This will oftentimes occur without the gas pedal being depressed and the driver accelerating the car. This is usually caused by unnatural resistance with the fuel pump motor and involves you needing to learn how to test the fuel pump. 

Decreased gas mileage 


If the relief valve in the fuel pump is not opening at the right times, then more fuel than is actually required will then flow into the engine system. If your vehicle usually gets decent gas mileage and great miles per gallon and then suddenly becomes a gas guzzler, then there could be an emergency in the fuel system. Make sure you take notice of how you fuel your car so that you can learn how to test the fuel pump in your vehicle. 

Engine will not start


When a fuel pump completely stops working, fuel can’t reach the engine on ignition and cause the car to start. If this occurs, then the engine will crank and rev but never catch and be able to start the vehicle. To learn how to test the fuel pump, you need to check for a blown fuse or low pressure within the fuel line. 

© 2022 Cash Cars Buyer. All Rights Reserved. Terms & Conditions | Privacy Policy | Sitemap