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.
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.