General: Everything you wanted to know about fuel pumps!

[elwesso]

Everything you wanted to know about fuel pumps!Fuel pump failure. Troubleshooting. Fuel Pressure Regulator (FPR). Diagrams.

By: Elwesso

Why do fuel pumps fail? Fuel pumps can fail due to a number of reasons. This article specifically targets gear rotor EFI type fuel pumps which are the most common fuel pumps found in vehicles manufactured after 1985.

The top reasons for fuel pump failure are contamination, overheating, and the gears in the the fuel pump wearing out over time. Rust, debris, and dirt are three common particles that can somehow enter the gas tank and be fed towards or through the intank fuel filter and possibly into the fuel pump. These particles clog up your fuel pumps filter making it work harder to pump fuel. This causes stress and accelerated wear on the dozens of small components inside the fuel pump eventually leading to fuel pump failure. When filling up with gas, make sure no loose particles are being pushed by the gas pump into the gas tank or onto your gas tank cap. When installing a new fuel pump, clean out any partials from the bottom of your gas tank and ensure that dirt does not enter it while reinstalling the fuel sending unit.

Frequently running your vehicle on a low gas tank is extremely bad for your fuel pump and fuel system components. On many vehicles, approximately 10-15 times the amount of fuel your fuel pump sends towards your engine gets sent back to your fuel tank. This helps cool down your fuel components and the fuel in your gas tank. By running on a low gas tank, the fuel in the gas tank heats up a lot quicker causing the fuel pump to overheat or even worse, run dry. Avoid leaving your gas tank low whenever possible. This is very crucial during the first few weeks after a new fuel pump install. A new fuel pump should be installed into a a minimum of half a tank full of gas.

A typical gear rotor fuel pump is made up of approximately 200 components. After several years of use, these parts can eventually wear out causing the fuel pump to fail.

Fuel Pump Troubleshooting FAQ

My car won't start. Do I need to replace my fuel pump?

In most cases, a vehicle's failure to start is usually caused by a faulty, battery, alternator, starter, or fuel pump. If the first three of these parts are determined to be working properly, have someone listen for a vibrating sound that the fuel pump should make near your gas tank when your engine is running. In some vehicles you may be able to hear this sound better by turning the ignition key barely enough to start the engine. If there is no fuel pump noise coming from the gas tank or the sound is very week, chances are that it's time to replace your fuel pump.

On nearly every Nissan the best place to start if you think its a fuel related issue is to check fuel pressure. You can get a standard fuel pressure gauge at nearly every auto store, and they are worth their weight in gold. You can either T a fuel pressure gauge in after the fuel filter or simply hook it up after the fuel filter, obviously the former is advised as you can run the vehicle while the gauge is installed. At idle, Nissan's should have around 35PSI and it should slowly increase to about 43PSI at WOT. My car is jerking while accelerating. Do I need a new fuel pump?

If it's not your engine's tuning, jerking is usually the result of a faulty fuel pump. Follow the same procedure above to listen for the fuel pump. On most Nissan, jerking is sometimes related to the MAF sensor.

Fuel Pump Product FAQ

What fuel pump flow rate (LPH) and pressure is suitable for my application?

Sending a larger flow of fuel throughout your fuel system will never harm your engine and may actually help your vehicle in several ways. Your fuel injectors and fuel pressure regulator will only allow what is needed to travel into your engine's intake manifold, usually sending back approximately 95% of the fuel from your fuel pump, directly back to your fuel tank via the fuel return line. This helps cool down your gas as well as fragile vehicle components as the fuel passes through. However, you must know the current draw of the larger fuel pump to make sure it is not significantly more. Most Nissan's use a multi-speed controller, and you can fry the controller if the larger pump draws more current.

What is a fuel pressure regulator?

A fuel pressure regulator (FPR) controls the amount of fuel that goes into the intake manifold via the vacuum line after it passes through the injectors.

How does a typical EFI (electric fuel injection) system work?Below is a diagram which we have drawn to show the basics of how your fuel system works.



1. Fuel Tank 2. Intank Fuel Filter 3. Typical Walbro Electric Fuel Pump 4. In-tank Fuel Line 5. Fuel Sending Unit 6. Fuel Level Meter 7. Outgoing Fuel Line 8. External Fuel Filter 9. Fuel Rail 10. Intake Manifold 11. Engine 12. Fuel Pressure Regulator 13. Vacuum Line 14. Fuel Return Line

How long do your fuel pumps last?Many fuel pumps should last 10 or more years. Please read above "Why Fuel Pumps Fail" guide for useful information on how to greatly increase the lifespan of your fuel pump.

Fuel Pump Installation FAQ

Where is my Fuel Pump located?On many Nissans, the fuel pump is inside the fuel tank, and the fuel tank is located behind the back seat. On vehicles that have fold down seats, it is probably under the trunk area. Consult your owners manual or service manual for exact locations.

What does my fuel sending unit look like?Below is an image of what the typical fuel assembly looks like. A fuel sending unit is where you mount your new in tank fuel pump. Please note that in most cases during installation, you will not have to disassemble anything other than the old fuel pump, hose, and positive/negative power connection.