No power to fuel pump

No eléctrical power to fuel pump

My car has 165000 miles.
My car has a manual transmission.

Experienced mechanics share their insights in answering this question :
Hello there, many faults will cause your 1985 RX-7 to not have power at the fuel pump. The most common faults are the ignition switch, a shorted wire, improper ground, or a faulty fuel pump. The first step will be to check the wiring visually to ensure it is in good condition and not broken going to the fuel pump. A qualified technician, such as one from YourMechanic, will be able to diagnose the loss of power and follow through with any needed repairs.

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Electrical issues: Electrical faults are also significant contributors to fuel pump failures. The most common electrical issues are rusted connectors, loose connectors, or melted wiring and connectors.
The basic way your modern electrical fuel pump works is by utilizing a DC motor in the pump assembly which draws in the fuel sitting in your gas tank. From there, it sends it up the fuel line and into the fuel rail where it can be injected into a cylinder. It then mixes with air and a spark to create combustion.
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.
Yes. A fault with the ignition switch can lead to the fuel pump not being energized with electricity.
Irregular resistance within the fuel pump motor can lead to your car slowing down and being unable to accelerate. Failing to accelerate is a good sign that your vehicle`s fuel pump needs inspection.
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 Pump Control Module communicates with the Engine Control Module over the vehicle`s Local Area Network. The ECM provides a 5-volt enable signal to the FPCM to enable fuel pump operation. A enable command is also provided initially for 2 seconds when the ignition switch is placed into the RUN position.
The ignition switch will momentarily provide power to the fuel pump and ignition system when it is in the cranking position, which may allow the vehicle to start. However, if it has failed in the “on” position, it will cut off power to the fuel and ignition systems as soon as the key is moved back to the “on” position.
If the fuel pump relay fails, it will cut off power to the fuel pump which will render it inoperable, and therefore silent, when the ignition is on. While the fuel pump relay is a very simple component, it plays a very important role in the proper operation of the vehicle.
Loose wiring, corroded connections, damaged starter components, oil leaks, and a bad relay or fuse are some of the reasons why a starter can fail. As the driver turns on the ignition switch, a current for the starter should flow and get the engine running. If not, the starter might be faulty and require replacement.
To confirm that your pump has failed, check the pressure in your fuel lines with a fuel pressure gauge; if it reads zero, then your pump is likely dead. You can also check your car`s fuse box; a blown fuel pump fuse is another reliable symptom of a failed pump.
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 most common reason a pump fails is wear on the pump from improper lubrication or over-use. The best way to explain a failed fuel pump due to wear and tear is to explain what other reasons may have lead to a failed pump: Most fuel pumps are lubricated by the fuel in the tank itself.
The most typical causes of a car not accelerating while driving include a faulty sensor, contaminated fuel or air filters, or a faulty timing belt.
The Fuel Pump Driver Module controls the voltage delivered to a vehicle`s fuel pump. By controlling the voltage, the module maintains optimal fuel pressure and fuel delivery to the engine throughout its full operating range.
A pipe called the fuel rail supplies pressurized fuel to all of the injectors.
The piston in the pump has two cycles, suction and compression. The solenoid on the side of the pump controls how much fuel is compressed during the compression stroke. During the suction cycle, the solenoid will allow fuel from the low-pressure side of the fuel system to enter the pump.
The reason is that the BCM feeds inputs into the Passlock (or other security system) for it to `determine` if it is being stolen or hotwired. For example: the status of the doors, interior lights, trunk status, etc. and in some cases can even control the fuel pump.
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.
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.
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).
The relay bypass switch plugs in place of the fuel pump relay and provides direct control over the fuel pump circuit. Relay bypass allows the technician to control fuel pump independent of all on-board systems.
1. Turn the ignition switch to position `0`. 2. Press down the rubber reset button on the top of the inertia switch.
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.

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.

Read Full Q/A … : No power to fuel pump

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.

Read Full Q/A … : No power to fuel pump

I put a fuel pump in and a fuel pump relay. The relay works but there is no power to the fuel pump.
ANSWER : Hi there. There could be an issue with the wiring to the fuel pump between the fuel pump relay and the fuel pump. Remove the wiring to the fuel pump and check the resistance from the wiring from the relay to the fuel pump. There should be no more than 1 ohm of resistance. If there is more resistance than 1 ohm, then there is a break or corrosion in the wiring. Also, check the ground circuit and make sure that the fuel pump is getting a proper ground. If you need further assistance with your fuel pump not operating, then seek out a professional, such as one from Your Mechanic, to help you.

Read Full Q/A … : No power to fuel pump

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 … : No power to fuel pump

Not getting power to the fuel pump and the secondary air injection pump fuse keeps blowing
ANSWER : There are quite a few reports of PCM (Powertrain Control Module, AKA computer) failures causing your problem, but before you go replacing the PCM, do some more pinpoint tests. This may require you to find a wiring diagram of all the wires coming from the PCM.

The first thing I would do is to connect a scanner to the car and see if you can communicate with the PCM. As a technician, I have access to communities of technicians where repeat failures are reported. In these reports, it is most common when the PCM fails in this fashion, that you will not have PCM communication. If you do have communication and the Check Engine Light turns on with the key on, I would be leaning away from the PCM being the problem.

However, this is by no means conclusive. You could be correct in your thoughts about a wiring problem mid vehicle. On most GM vehicles, there is a connector along the frame rail for the wiring harness that services the fuel module in the tank. This has problems with corrosion because it sits under the vehicle exposed to the elements. But why am I doubtful of this, and this will require you to confirm where the power starts and stops, is you stated you didn’t have power from the fuse box. This would be before this connector and the fuel pump. If this is the case, I wouldn’t be thinking of a wiring problem mid vehicle anymore.

I am wondering if you confirmed the fuse box was getting power? It is a very common problem that when we move wiring we inadvertently move the damaged wiring and fix the problem for the short term. You may have done this when replacing the fuse box. Not to mention you seem to have an intermittent failure on your hands. This compounds the process quite a bit.

I’m not sure how you are confirming you have power at the various points, but I highly recommend a test light over a multi-meter. A test light draws current and a multi-meter does not. There can be voltage present but not a good enough connection to carry current. This is a very important distinction when you are battling bad connections. The problem with a test light though, is knowing when it shouldn’t be used. Some test lights draw too much current and can damage computer modules. Even us technicians perform tests on modules at our own risk.

The best way to test a relay is to simply use a jumper wire to bypass them. If I suspect there is a problem with the power supply to the fuel pump, this is the first thing I do. This way I can be sure it isn’t the relay or the PCM that turns the relay on. If the fuel pump does not run, use the before mentioned test light to find where the power stops. This requires you to methodically track the wire back to the fuel pump. I usually start at the central connector, if it has one. Not all of them do. I go directly to the pump if I can, but this is often not easy to access without dropping the fuel tank down. If you successfully confirm power to the pump, it maybe a bad ground, in which case the easiest way to confirm this is to add a ground yourself.

If this circuit checks out good, a few other things to check are power and ground to the PCM. Locate the wire from the PCM that powers the fuel pump relay. This can be done at the relay connector while you are testing the fuel pump circuit without the relay. When you turn the key on, on of the four terminals should receive power from the PCM for a few seconds. It will turn off after a couple of seconds if the PCM doesn’t see a signal that the motor is running. This is normal operation.

As for the air pump, I wouldn’t think this is an indication of the problem unless this occurred at the exact same time as the fuel pump failure. If so, I would suspect a wiring harness is shorting to ground somewhere. If they didn’t occur at the same time, this is most likely a separate issue.

The challenge you have here is isolating each part of the system. The PCM, the fuel pump relay, or a wiring issue. The PCM is actually fairly easy to check. Is the Check Engine Light on with key on and does it communicate with a scanner? Then follow the fuel pump relay test I outlined above. If it is a bad connection somewhere in the system, you will need a good wiring diagram and a well thought out plan to isolate where the problem is. This can be the most difficult to diagnose, especially if the problem is intermittent. Find a wiring diagram and study it carefully. If you’d like help, you can have a qualified technician, such as one from YourMechanic, to inspect your car’s loss of power and make the correct repairs.

Good luck. I hope I have been of assistance.

Read Full Q/A … : No power to fuel pump

changed the fuel pump on 1999 dodge ram 2500 diesel fuel truck. Now, it doesn’t send power to fuel pump.
ANSWER : At key on, the fuel pump is normally only powered momentarily to pressurize the system. If you are testing during this brief interval, you have to apply a volt meter at the instant the key is turned on. Otherwise, the circuit will be normally open until the vehicle actually starts. If you are detecting momentary power during that window, then your no start condition is "probably" not related to a fault in the pump circuit.

If you detect no power at ANY time to the pump (including during key on), your only recourse is the Factory Service Manual wiring diagram. With the diagram in hand, you have to trace the fuel pump circuit from the power source to find the interruption. There may be a fusible link in the circuit; also check the pump ground. Obviously check the wiring harness and plug connections as those were handled during the repair. You can probe the new motor terminals to see if they are open. If the motor is good, you should find a small winding resistance of maybe 3 ohms or so (varies from pump model to pump model).

If you desire a mobile repair for this, simply request an electrical diagnostic and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Read Full Q/A … : No power to fuel pump

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.

Read Full Q/A … : No power to fuel pump

Replaced fuel pressure regulator and fuel pump,still no power going to fuel pump
ANSWER : This sounds like you may not have any power going to 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.

Read Full Q/A … : No power to fuel pump