Fuel Pump not coming on

I have replaced my fuel pump and relay but fuel pump is not coming on when I turn the key over. I am getting power and ground to pump. What else could this be?
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
You say you are getting battery power and ground to the fuel pump but the pump is not coming on? If this is the case, then the pump connector is bad. There is a technical bulletin that the connector should be replaced when a new pump is put in. The connector gets overheated and the plug will not fit the pump pins tight enough. When you test the plug, it will get power but not be able to power the new pump.

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If you there is no power to the fuel pump or the relay, then there may be a possible electrical issue with the vehicle. I would first verify that the main EFI, fuel pump, and ignition fuses are not blown, as these can sometimes cut off power to the fuel system.
If there is no power, the fault is in the relay again — probably the contacts are burned or stuck in the open position. Burned contacts can also fuse together, so that they stick in the closed position, so the component does not switch off. In either case, replace the relay.
Powered by the ignition and/or powertrain control module (PCM), the fuel pump relay`s main function is to provide the fuel pump with enough power. When the fuel pump relay isn`t working, then the fuel pump cannot either.
Another symptom of a faulty fuel pump relay is an engine that does not start. If the fuel pump relay fails the fuel pump will be left without power. The engine may still crank when the key is turned, however it will not be able to start due to lack of fuel.
Fuel pump failures can be caused by electrical faults, old age (wear) or fuel contaminants (dirt, moisture or bad gas). Fuel pump failures often occur without warning. Fuel pumps, injectors and pressure regulators are the three most commonly replaced fuel system components.
Once the vehicle determines the systems are safe, then the vehicle allows you to restart. The fuel pump shut-off switch is located behind an access panel on the right side of the luggage compartment. The fuel pump shut-off switch has a red reset button on top of it.
The main drawbacks are loose contacts, cracks in the contacts, or excessive size and position deviation. This will affect the contact reliability of the relay. The faults of contact components generally include contact overheating, wear, and welding.
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.
Yes. No fuel pump relay = no fuel pump. No fuel pump = no fuel. No fuel = no start.
Without this relay, the engine would not receive fuel while starting. The pump that delivers fuel to the engine while the engine is running requires electricity in order to operate. This electricity is created by an oil pressure device in the engine.
Water in the fuel will destroy the fuel pump

The moisture from the gasoline attacks the metal components in the fuel pump and will cause it to fail.

The PCM will ground the fuel pump relay which supplies power to the fuel pump under some specific circumstances. As a car sits, the fuel pressure gradually decreases and modern cars don`t run without fuel pressure.
Easy…… use a push button as a start with one of your relay contacts(or an aux relay) as a hold-in across the start button. Your float switch then becomes a series stop switch. The latter would of course have to be normally closed during normal operation.
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.
If the relay fails it will cut off power to fuel pump and ignition system, which will result in a no power, and therefore no start condition. You may find that turning the key may power on the accessories, and may even crank the engine.
One disadvantage of solid state relays is their tendency to fail “shorted” on their outputs, while electromechanical relay contacts tend to fail “open.” In either case, it is possible for a relay to fail in the other mode, but these are the most common failures.
Realizing that 85 and 86 are the coil pins, these pins will be transferring the current through the coil. 85 will be used to ground your relay, while 86 will be connected to the switchable power. 87 and 87a will be connected to your controlled accessories that you wish to turn on and off with your relay.
A stuck relay will not start working properly again on its own. It will require repair or replacement. While we support homeowners learning about their HVAC system, consider hiring a professional air conditioner repair company when you have a stuck relay, especially considering it relates to your home`s electricity.
If you removed a fuse or breaker for the ignition or fuel injection systems, the car wouldn`t start (assuming it`s a gasoline-powered vehicle).
Electronic Control Unit (ECU)

The ECU is the brain of the operation. It uses engine RPM and signals from different sensors to meter the fuel. It does this by telling the fuel injectors when and how long to fire. The ECU often controls other functions like the fuel pump and ignition timing.

The fuel tank pressure sensor is part of the fuel pump assembly and is mounted on top of the tank or inside the tank. It`s part of the evaporative emissions system (commonly referred to as “EVAP”) and reads pressure in the fuel system to detect evaporative leaks, such as a loose or faulty gas cap.
A voltage of at least 12.5 – 13.0 volts must be present when the engine and pump are running. If the measured voltage at the terminals or the plug of the pump is significantly lower than the on-board voltage, e.g. lower than 11 volts, there is a malfunction.
The voltage drop occurs because of resistance in the circuit that supplies the pump. The resistance could be in the connectors, grounds or harness. A resistor or insulator prevents the flow of electricity in a circuit. Resistance can be caused by corrosion, fretting and even air.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

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.

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Engine crank, no coil spark, fuel pump does not kick in.
ANSWER : Hi there. There could be multiple issues causing your lack of spark problem, ranging from a minor electrical short in the main relay to an issue with your ECU. In order to know for sure, you should have a professional mobile mechanic complete an electrical problems inspection.

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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.

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I have a 1981 e-350 with dual fuel tanks the p.o. added a third tank and 3 electric fuel pumps along with sepparate gauges and swi
ANSWER : The switch you are referring to is vended with the required electrical and fuel schematic (I just looked in the box) that answers your installation question. If you want an advance view, here is a link as well. Yes, you need a return line and just refer to the aforementioned link. If you are retrofitting back to OEM, I strongly encourage you to buy the original Factory Service Manual (FSM). There are lots of details attending this system and obviously it is difficult to recount it all here. The FSM will make your life much easier and you can then make sure your installation is perfect. Alternatively, YourMechanic can dispatch a certified mechanic and perform the whole retrofit and check out if you desire. Just request and schedule a generic service such as fuel pump service and the mechanic will come to your location and estimate the parts and labor required. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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Fuel pressure
ANSWER : Hello,
You may want to try checking the fuel pump relay. The relay wires should have ground on two wires, power on one wire and switched power on another wire. To activate the fuel pump your ECU actually connects one of the ground wires to complete the circuit and send power to the fuel pump. If the wires all have power running through them, then it is likely you have a faulty relay. The wire coming from the fuel pump is the other ground wire. I would recommend having an expert from YourMechanic come to your location to diagnose your wiring as this can be very difficult and time consuming without the proper wiring diagram.

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Fuel pump is not coming on when try to start the vehicle.
ANSWER : Hello there, thank you for asking about your 2007 Chevrolet Cobalt. If you jump the fuel pump relay and still do not get fuel pressure, then you may have wired the fuel pump in backwards. The pump may be running backwards and not sucking in fuel. You need to make sure you installed the pump wiring correctly. If you need help from a certified mechanic, you can have your fuel pump installed by a technician from YourMechanic at your home or office.

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Installed new delphi fuel pump and fram fuel filter. still no pressure on fuel rail valve and wont start. 2003 Chevrolet Tahoe
ANSWER : Hi there – I suspect you have weak power getting to the fuel pump. I would first check the voltage coming out of the fuel pump relay. If the contacts in the relay are burned, you will not get reliable current flow to the pump. Check the fuel pump ground as well (voltage drop across the ground, not just continuity). I recommend a fuel system inspection performed 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.

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Car only runs when jumper the fuel pump
ANSWER : Check to see if you are getting power when you test the green with orange stripe wire going to the fuel pump module. If you have no power then check the the fuel inertia switch, in the left kick panel, by the drivers foot, and see if the inertia switch is not tripped. If it is, reset it and the pump should work.

If the switch is okay then make sure it has power to it and from it, when cranking the engine. If you have no power then check the fuel relay and see if it has power to it and that it’s being turned on when you crank it. If you do not then you may have an issue with the computer not activating the fuel pump. This will require a scan of the system and in-depth tests further than the scope of what this diagnoses is capable of. You will need a wiring diagram to follow and a scanner to activate the relays to test the system.

If you decide to get this fixed, contact a certified mechanic who can perform all of these checks in order to find the root of your starting problem. Once this is done, an accurate repair can be made.

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