I replaced the fuel pump and now my truck won’t start

I recently replaced the fuel pump and now my truck won't start. When the fuel pump is hooked up on the tank, no fuel is pushed through, but I can hear the pump running. However, when I disconnect the fuel pump and hook it straight to the battery, the fuel pump sprays fuel out. I've checked and both the relay and the fuse are good. What else could be the problem?

My car has 200000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
Hi there:

In some cases, when the fuel pump is not supplying fuel from the tank to the fuel injectors it’s due to one of three different issues. First, it’s possible that the pump or some of the hose attachments are installed backwards or that there is a blockage somewhere in the fuel lines; typically at the first fuel filter. Finally, it’s possible that you have a ground issue somewhere near the fuel pump that’s causing a reduction in power. The best way to trace this issue is to contact a mobile mechanic and have them help you diagnose this issue; as the process for tracing a fuel pump delivery issue can be complex and very time consuming.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

If your car doesn`t start with a new fuel pump, chances are the fuel pump is either not hooked up right or is broken. Double check that the pump is correctly installed and all hose attachments are plugged in. Next, check for any blockages along the fuel line—this can also cause your car not to start.
There are several reasons why your fuel pump may not be working after replacing it. The most likely reason is that it was not installed properly. Double-check that it is securely hooked up to all fuel lines and electrical wires. One common mistake people make is installing the pump upside down.
The most common reasons a Nissan TITAN won`t start are a dead battery, an alternator problem, or failed starter. Search our network of RepairPal Certified shops near you to speak with a technician about your issue.
Difficult Starts

If your vehicle`s fuel pump cannot get gas from the tank to the engine, you will have trouble starting your car. The car will struggle to start and run because the pump cannot push enough gas through. A worn pump loses its pressure and the engine is being starved of gasoline.

Note: The fuel pump shut off switch reset button is usually located either under the dash in the driver compartment or under the driver or passenger seat. Just move the seat forward and pull back on the carpet or popping off the cover under the seat to access the switch.
A poor connection can cause enough resistance to lower the amount of voltage reaching the pump. This causes the pump to turn more slowly than it should, and can shorten the life of the pump. Replacing the vehicle side connector should solve the issues with poor connections, but sometimes causes another problem.
Why won`t my car start but I have power? If you attempt to start up your car but the engine won`t turn over and the dashboard lights up, then you most likely have an issue with your battery. You could have a damaged or corroded battery terminal, which is stopping the engine from starting up when you fully turn the key.
If the car cranks when you turn the key, but the engine won`t start, it could be because fuel isn`t getting to the engine. One potential reason for this could be dirty fuel injectors. Over time, the fuel injector nozzles can become clogged with rust, corrosion or debris.
The cause of this problem is usually one of 3 things – a failed starter motor, a bad connection between the battery and starter motor, or a blown fuse (if present) in line between the starter and the battery.
when you switch the ignition on, the fuel pump situated inside the fuel tank starts pumping fuel to the engine. so yes, it DOES run even when the engine is off, when the ignition is on.
The basic operating system for an electric fuel pump is relatively simple. When the key is turned on, the powertrain control module (PCM) closes the fuel pump relay, which activates the fuel pump for about three seconds to pressurize the fuel injectors.
Once the switch has tripped it must be reset before attempting to restart the engine. The inertia switch is located behind the trim on the left-hand side of the vehicle, forward of the front door post, below the fascia. A finger access hole in the trim allows the driver to reset the switch. !
In contrast, the fuel pressure created by mechanical fuel pumps is much less, usually in the 1–4 psi range. Second, this is important because the fuel system needs to be primed—the lines between the tank and the engine have to be filled with fuel.
No need to bleed. Just turn the key to position 2 a few times to activate the fuel pump and fill the rail. That`s about it.. Check for fuel pressure if it still won`t start.
The Fuel Pump function is used where the ECU will be controlling an electric Fuel Pump. ECU control is preferred for safety reasons to ensure that the fuel pump is turned off in case of an accident.
If the pump makes no sound, the good news is the cause might be a blown fuse. Locate the fuel pump fuse and relay. If it`s blown, replace the fuse with another of the same amperage.
How do gas pumps know when to stop? As gasoline enters the tank, air begins to exit it. Gas pumps stop when there is no more air flowing through the nozzle and the change in air pressure causes the nozzle valve to shut automatically.
The switch will usually come with a reset button that will reactivate the fuel pump if the switch was tripped. The fuel pump switch is an electrical component, and just the same as the rest on the vehicle, over time it can wear out and develop issues.
As with most vehicles, the 2005 Nissan Titan`s fuel pump relay is located in the fuse box in the engine compartment.
Bad Alternator

If your car won`t start, but your battery is fine, chances are you have a bad alternator. This is another charging system issue, like a dead battery, that won`t let you start your car.

Flat or faulty car battery

A flat battery is the most common reason your car won`t start and can be caused by a number of things, such as lights being left on, something in the electrical system causing a battery drain, or even a faulty battery that won`t hold its charge.

One common culprit for this problem is the crankshaft position sensor, which measures the position and speed of the crankshaft. The computer uses the information from this sensor to know when to fire the spark plugs. If the sensor isn`t working, the spark plugs won`t fire, keeping the engine from starting.
A Bad Crankshaft Position Sensor

The crankshaft position sensor monitors the position and rotational speeds of the crankshaft. Without the crank sensor, the engine control module (ECM) wouldn`t know when to fire the fuel injectors and ignite the spark plugs.

Your engine won`t start at all – Simply put, if the pump has indeed failed, you will not be able to drive your car. Without fuel, the motor won`t be able to run. An engine can also fail to start for various other reasons, including a dead battery, alternator, starter, or even a clogged fuel filter.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

I replaced the fuel pump and now my truck won’t start
ANSWER : Hi there:

In some cases, when the fuel pump is not supplying fuel from the tank to the fuel injectors it’s due to one of three different issues. First, it’s possible that the pump or some of the hose attachments are installed backwards or that there is a blockage somewhere in the fuel lines; typically at the first fuel filter. Finally, it’s possible that you have a ground issue somewhere near the fuel pump that’s causing a reduction in power. The best way to trace this issue is to contact a mobile mechanic and have them help you diagnose this issue; as the process for tracing a fuel pump delivery issue can be complex and very time consuming.

Read Full Q/A … : I replaced the fuel pump and now my truck won’t start

Replaced fuel pump. Car won’t start. 2002 Infinity I35
ANSWER : Hi there – the metal component you describe is a fuel check valve on the fuel return line. Its function is to maintain a small amount of pressure in the fuel system so that starting does not require the fuel pump to run very long before the engine will start. Having replaced the fuel pump and fuel filter, I would check fuel pressure while the car is running. This is to check the fuel pump relay for burned contacts that won’t support full electrical current to the pump, and for proper fuel pressure – a malfunctioning fuel pressure regulator could also restrict power and higher speeds if pressure is too low. I would recommend an inspection of the fuel system by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

Read Full Q/A … : I replaced the fuel pump and now my truck won’t start

1993 Ford F150 4.9 straight 6 fuel pump keeps running, won’t start, replaced relay and fuel pressure regulator, still having the same problem
ANSWER : Hi, thanks for writing in. You need to have the fuel pressure checked to see if the pressure is low. The fuel pump inlet screen may be getting clogged causing the pressure to drop off but the pump will continue to run. You may need to replace the pump if it is not producing enough pressure. If you have dual tanks then you may have a defective switching valve in center of vehicle on frame. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to test the system for you, and make or suggest any repairs as needed.

Read Full Q/A … : I replaced the fuel pump and now my truck won’t start

Just replaced my fuel pump but its not getting any power tested fuel pump relay and fuel fuse both good tested the wires all good.
ANSWER : You need to look at the theft light on dash to make sure it comes on and goes off when you turn the key to the on position. If light comes on and stays on then your theft system is causing the fuel pump to not be engaged. I recommend you check the theft system and then scan the computer for theft system codes. You may need to reprogram the keys to work or you have an bad sensor for the ignition key in the steering column.

Read Full Q/A … : I replaced the fuel pump and now my truck won’t start

I have a truck that won’t run and is not getting gas to the engine. Fuel pump is running, have a new filter and new fuel pressure
ANSWER : Hi There,
It sounds like you may have a clogged fuel injector or potentially a faulty injector that is fried internally. I would suggest testing them if you have access to a multi meter. Disconnect the injector from the electrical connector and set your multi meter to Ohms mode and measure the resistance of the injector. After testing all injectors, compare the resistance. They should be the same or very close. If they are not, they will likely need to be replaced.

Read Full Q/A … : I replaced the fuel pump and now my truck won’t start

My car stutter starts, but only after driving it for a few minutes.
ANSWER : Hey there. This may also be caused by what is called the fuel pressure regulator. This is a unit that helps to maintain the fuel pressure at the proper level. When this is not working properly, the fuel pump may be pumping properly, but the fuel may not arrive at the fuel injectors at the proper psi. When this happens, this can cause a lean fuel condition which may cause the car to hesitate, misfire, or stall. If you would like to have an expert pinpoint the issue, a certified professional from YourMechanic can come to your car’s location to inspect the hard start problem and confirm which repairs are needed.

Read Full Q/A … : I replaced the fuel pump and now my truck won’t start

I changed fuel pump and truck ran great for 3 days. Now after 3 days truck dies. It will start runs few min then dies like before
ANSWER : Check the bottom of the fuel tank for sediment. Age and mileage could have accumulated a lot of it at the bottom of the tank. If you did not, check and change the fuel filter. Rule of thumb – replace the fuel filter any time you replace a fuel pump. Also, check the wiring for any chaffing on the fuel pump when you remove it. While your problem is kind of unique, I have seen many GM truck fuel tank baffle loosen over time, occasionally rubbing against the fuel pump can intermittently short it out and/or block the fuel pump pick up. To have this diagnosed, consider having a certified expert from YourMechanic inspect the stalling issue to have this corrected.

Read Full Q/A … : I replaced the fuel pump and now my truck won’t start

Odometer has lines, won’t start unless I put fuel in the intake. The fuel pump keeps running and doesn’t shut off? Seems like the truck wants to start.
ANSWER : Hi there. From the description you have provided, you’ve replaced the fuel pressure regulator, the fuel pump never shuts off and puts fuel in the throttle body, it runs until the fuel is gone, and the odometer has lines instead of mileage. This would appear to be a fuel control problem and communication failure.

Some possibilities are that the PCM (Powertrain Control Module) has shorted internally causing the fuel pump relay to be commanded continuously on, injector driver circuits are inoperative, or failed communication to the IPC (Instrument Panel Cluster).

This all needs to be confirmed through diagnostic procedures. I recommend having your vehicle’s fuel pump never shuts off, truck won’t start condition be diagnosed and repaired by a certified technician, such as one from YourMechanic.

Read Full Q/A … : I replaced the fuel pump and now my truck won’t start

Eric smoalih

I am a certified master technician with the National Institute for Automotive Service Excellence (ASE), and I have been working as an auto mechanic for over 15 years. I am passionate about my work, and I take great pride in helping people keep their cars running smoothly.