Last Updated On: July 8, 2017

Car Cranks But Won’t Start. How-To Recognize a Bad Fuel Pump

My car gave me no indication of a problem when I shut it off but now my car won’t start.

How do I locate the problem and I need help to know How to recognize a bad fuel pump or ignition problems.

It can be a scary feeling to get into your car and turn the key and hear the engine turn over but not start. People with this situation want to know what the problem is, so they then can make a better decision to fix it themselves or take it to a mechanic.

Troubleshooting A No Start Car For Car Owners

Car Won't StartIf you have no mechanical skills, your next step may be to call a tow truck and send the vehicle to repair shop. However, before you send off the car, you may want to have an idea of what the problem may be.

Alternatively, you may have enough mechanical ability to do minor repairs, but you may need a little help with what to do when your car will not start, and you need to locate the problem.
In this article, we will address the most common causes associated with automobile restart problems that you can check, with no or very little mechanical skills.

In this article, we will show you how to check your cars:

  • Fuel pump
  • Fuel pump fuses
  • Fuel pump relays
  • Resetting a fuel pump circuit breaker
  • Crank sensors
  • Ignition problems

We will also describe the process to replace a bad fuel pump.

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Car Cranks but Won’t Start or Re-Start!

If you have stopped to fill the gas tank and the car will not start. Alternatively, you have done some shopping and when you returned to the car, the engine will crank over but won’t re-start, then there are a few things you can check first.

  1. Turn off the radio and close the windows to eliminate any noise in the car.
  2. Next, turn the key, so the gauges and warning lights come to life, but don’t start the engine.
  3. You should hear a buzzing sound coming from where the fuel tank is located when you turn on the key.
  4. This sound could be from under the car or in the back near the trunk.

The buzzing sound you are listening for sounds like an electric motor running. This sound is the electric fuel pump trying to prime the fuel system.

It will only run for a few seconds and then shut off, so if you are not sure you could hear it or if there is noise outside, you may have to try it several times. Turn the key on and wait then turn it off.

If there is no noise outside of the car you may need to try this with the car door open so you can hear under the car.

Do this until you are convinced that you either hear the pump running or you do not.

Many people recognize this sound every time they start the car but don’t realize it is the fuel pump running.

  • If you “Do” hear the fuel pump running then you can skip down to “Checking the Tachometer Section of this article.
  • If you “DO NOT” hear the buzz of the fuel pump, then your engine has no fuel pressure, and we need to see why.

How To Determine If Your Fuel Pump Is Bad

The first thing you want to do is check the fuse panel to see if the fuel pump fuse is blown.

If your car has two fuse panels than the one in the engine compartment should be the correct one to check.

The fuse panel or circuit box is usually located near the battery and is a small black box with a removable lid that is labeled. Inside the cover, you can find the fuse index if provided.

Fuse Panel IndexMany manufacturers list the fuses by number and position inside the lid. If your car does not list the fuses in the lid, you will have to check your car’s owner manual for fuse and relay locations.

Whenever you purchase a new car or lease a car, you should always familiarize yourself with the fuse panels and where they are located.

Pull out the fuse for the fuel pump and hold it up to see if the element if broken. If so, you can replace it. Some fuse boxes supply extra fuses that you can use. Just make sure you use the same color fuse or one with the same AMP number listed on the top.

Fuel Pump FuseIf the fuse is good then you will need to check the fuel pump relay next. You can find the fuel pump relay in the same circuit box. It will also be labeled on the box lid or in the owner’s manual.

Check Fuse Box

Check Fuse Box 2

Without proper test equipment you won’t be able to test the relay but many of the relays in the box are the same AMP rating and size. If you switch the relay with a different one of the same size and rating, ( same amount of prongs on the bottom )  than you can try to start the car or listen for the fuel pump to run with the key on.

This will let you know if your fuel pump relay is bad.

Some of the other relays, such as horn or lights, can be switched. If this test works and the fuel pump runs, just remember to replace the bad relay before you drive the car.

Fuel Pump Circuit Breaker Reset

Some cars have a fuel pump circuit breaker instead of a fuse. If you cannot find a fuel pump fuse, then check your owner’s manual for the location of the fuel pump cut off breaker. It is usually located inside the car, down by one of the plastic panels or center console by your feet.

Fuel pump circuit breakers are designed to trip in the event of an accident or circuit overload to cut off the fuel pump operation. Fuel pump breakers usually have a button on top that pops up when it trips. Simply push this button back in until it clicks. The exact location of the breaker can also be found in your owners manual.

Check The Fuel Rail For Fuel Pressure

If the fuse is good or the circuit breaker is not tripped, then the next thing you can check is the fuel rail on the engine for proper fuel pressure.

Car Won't Restart After StoppingIf you have no mechanical skill and don’t want to get your hands dirty, then this is where you will want to have the car brought to a repair shop.

Even though you do not have the desire to fix the vehicle yourself, you still know what the problem is, and this is helpful in getting a proper estimate from the repair shop for a fuel pump replacement.

Keep in mind that the purpose of this article is to assist you in finding the possible cause of you trouble and is not intended to be a do-it-yourself guide to repairing parts of your car you are not familiar with.

With limited mechanical knowledge, you can diagnose the problem and be better prepared to deal with the dealer service department or repair shop if the repairs go beyond your ability.

How Do I know If My Fuel Pump Is Working?

Fuel Rail Valve

If you have some limited mechanical ability, then you can check the fuel rail yourself.

The fuel rail is a small tube that is located at the fuel injectors. The fuel pump pressurizes this tube through a fuel line from the tank and feeds the fuel injectors. It will have a small valve mounted on the line called a Schroeder Valve.

It is a small valve designed like the tire valve on your car’s tire. The location of this valve is usually near the fuel injectors, but I have seen them mounted along the fuel line at the firewall as in one of the two pictures below.

 

Caution. Protect your eyes in the event of a small amount of fuel spray when you probe the Schroeder valve needle under the cap.

Caution. Your cars Freon lines have the same type of valves. The correct valve goes to the fuel line that feeds the fuel injectors. Do not mistake the A/C lines for fuel lines.

Testing the fuel rail for fuel pressure:

  • Make sure the ignition key to the engine is turned OFF.
  • Remove the plastic cap on the Schroeder Valve attached to the fuel rail.
  • Slightly depress the needle valve. You should see a small amount of fuel spray  from the valve under pressure.

Test Fuel Pressure

Schroeder Valve

If there is little or no pressure at the valve, the pump has not pressurized the fuel line and the electric fuel pump is most likely bad.

Open Throttle BootAt this point many mechanics will open the rubber boot at the throttle body and spray a small amount of starter fluid into the manifold, reinstall the boot and try to start the engine. In most cases, the engine will start and run for a second or two, then shut down.

This verifies that if the engine were getting gas, it would start correctly. This also verifies that the engine has no fuel pressure.

Now that you have determined that the fuel pump is not working, you can decide if you have the necessary skills to replace it yourself or take the vehicle to a repair shop to have the pump replaced.

Replacing a Fuel Pump

Most electric fuel pumps are located in the fuel tank and are built as a fuel sending module. This fuel pump unit is easy to change once the tank is removed.

The steps you need to perform to replace the fuel pump or gain access for testing a fuel pump unit are:

  • Gain access to the fuel tank- This may include lifting the car or placing it on jack stands.
  • Drain the fuel from the tank- This is usually done with a siphon hose through the filler neck rubber connecting boot.
  • Remove the tank from the car- You will need to disconnect the fuel filler neck and vent lines, support the tank with a floor jack or similar device and remove the metal support straps. Then slowly lower the tank a few inches until you can see the fuel lines and wire harnesses mounted to the fuel pump.
  • Unclip the wiring harness and unhook the fuel lines- The fuel lines can be disconnected with a simple plastic tool that can be purchased from your local auto parts store. Simply follow the instructions that come with the tool.
  • Unlock the fuel pump from the mounting flange– Then carefully remove it from the tank along with the fuel float.
  • Install the new fuel pump- in reverse order.

Fuel Pump UnitEach car manufacturer and model carries a different style of fuel pump specially designed to fit your tank.

Each replacement fuel pump comes with easy to follow instructions for removal and replacement that will go into greater detail than this brief description.

Proper Care Will Prevent a Fuel Pump From Failing Prematurely.

Electric fuel pumps run continually with your engine, delivering high-pressure fuel to the fuel rail and injectors. To keep the pump motor cool and well primed they are designed to stay submerged in fuel. If you make a habit of running your tank all the way to empty before filling up, your fuel pump will most likely die before its designed life span.

This is due to the fact that when you shut off the engine with a low fuel level, the fuel can drain from the priming chamber designed into the fuel delivery system. So when you restart your car, the pump runs hot and un-primed until it can refill the fuel chamber.

Over time this will burn out the pump motor.

This is why many pumps fail right after shutting off the car and restarting it while it is hot. Like when you stop to refill the tank with gas.

To prolong the life of your fuel pump, don’t let the fuel level of your tank drop below an eighth of a tank of gas before refilling. This will prevent the pump from losing its prime and keep the pump motor cool.

Check The Tachometer, Other Ignition Problems

If your car won’t start but you can verify the fuel pump is running than the next thing you can easily do is check your cars tachometer if you have one. A common problem with a no start engine is the crank sensor. This sensor monitors the revolutions of the crankshaft and reports to the cars computer when to fire the spark plugs. Obviously, if the sensor fails, you will lose engine spark.

Ignition SparkEngine spark can be easily checked by removing a spark plug wire and lay the rubber insulator of the wire on a metal surface of the engine like an exhaust manifold bolt head. Have someone crank the engine and see if a spark shoots out of the end of the wire insulator and jump to the grounded bolt.

Don’t hold the wire in your hand when you do this or you will get a pretty sweet shock if you lean on the car.

If you see a blue spark or hear a snapping noise coming from the end of the wire, then you have a good spark, and the problem must be with the fuel delivery system.

Checking A Crank Sensor With A Tachometer

When you turn the key, and the engine starts to spin, you should see the tach needle bounce or move slightly. If it does not move, you could have a bad crank sensor. However, this test does not always work with all brands of cars and bad crank sensors in most cases will give a trouble code. This can also be seen with a diagnostic code of PO335 – PO339

TachometerMost auto parts stores will assist you by scanning your cars trouble code at no charge.

No spark can also be caused by a bad PCM, park/ natural switch at the transmission shifting linkage, bad ignition coil or ignition control modules.

Car Engine Cranks But Will Not Start

Most no start problems will not be caused by bad spark plugs, plug wires or gas delivery problems caused by plugged filters and such.

These types of problems always start with early warning signs like:

  • Engine loss of power.
  • Sputtering.
  • Slow starting.
  • Misfiring.
  • Engine check light warnings.

If your engine was running fine with no hints of trouble, then you find it just will not restart, you will most likely find a problem not related to typical maintenance issues. This is where dishonest repair shops will try to sell you other repairs that are not needed to fix any start problem.

You may not have the ability or mechanical skill to make the repairs yourself, but it is good to know what you are up against when you take your car in for repairs to prevent unnecessary repair costs and find out when a dishonest mechanic is trying to take advantage of you.

We hope these simple tips have helped you locate a bad fuel pump and assist you with knowing what replacing a fuel pump entails. Or you may have found a no spark issue and need an ignition control module or a crank sensor. Either way, you now have a better understanding of what the problem is and will aid you in determining if you want to tackle the job yourself or send it to a garage.

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