When a fuel pump runs for only a couple seconds then stops, it is likely something within the electrical system or fuel pressure control. The newer fuel pumps have a built in regulator and are designed to turn on for a few seconds when the ignition is turend ON, letting only 40-60 psi of fuel pressure build up. Here is an overview of whether the pump stops running too quickly, which can indicate a problem with the fuel pump relay or fuse. A relay is used and when the pump control module cannot properly power the pump, it tries to limit current to protect the pump which then in turn causes some of these electrical components to over heat, this most common failure point. Automotive experts suggest that 10-15% of pump failures can be traced back to an electrical problem, such as a bad relay or blown fuse.
At a less likely basis, it can be due to a bad fuel pressure sensor. This “rail pressure sensor” samples the fuel pressure inside the fuel rail and tells to ECU (Engine Control Unit) when it has reached enough fuel pressure. Simply put, if there is a malfunction within the sensor reading or the reading is incorrect you will have a situation where the pump can be turned off prematurely. Sure, in some cars, the sensor might require pressure to be within 5-10psi of pricing before it tells the pump to stop -- at which point your engine is now out of fuel economically. A new sensor will allow the pump to operate normally as well prevent any additional shutdowns that would be caused from a failing part.
Fuel filters which are clogged are another common reason why the pump will block. Since the impurity that blocks this filter generates backward resistance, which increases pressure, it forces the pump to work at higher currents and overheating followed by shutdown. To maintain full flow and ease the strain on pump, it is recommended to replace fuel filters every 30k miles. In fact, 20 percent of fuel system problems on vehicles over 100,000 miles are caused by clogged filters and a dirty filter can even have a detrimental impact on how quickly your car starts.
Dies after a few seconds: The fuel pump may run for less than a second, then dies – This also happens due to communication failure between the ECU (Engine Control Unit) in cars and the fuel pump. The ECU in some cases will shut down the fuel system completely if it registers a fault on the fuel system, and would not necessarily prompt continued delivery of fuel. Reprogramming or resetting of the ECU (engine control module) often resolves this problem, especially in newer cars with advance systems involved during fuel delievery in engine.
Over 100,000 were recalled by Ford in 2019 over a software bug in the ECU that caused fuel pumps to turn off too early--a reminder of how crucial the communication between fuel system and electronic controls is for proper operation. It is an example of how sophisticated systems can, paradoxically, be vulnerable to stoppages from unexpected forces.
In the words of Henry Ford "Failure is simply the opportunity to begin again, this time more intelligently. Resetting a fuel pump that turns on and off is not easy; typically, you have to start with the electric parts diagnostics and pass through verifying there is nothing blocking your passage with the piping of this system. Ensuring regular maintenance and diagnostic checks of the truck not only saves on major future repairs, but also keeps it running at its best.
We hope that we shed some light on fuel pump operation and diagnostics for you in this article, visit Fuel Pump, to learn more.