Guides to Change Engine Fuel Pump

by Generator D. Diesel Generator

Every vehicle is equipped with a fuel gauge to tell the driver how much fuel is left in the fuel tank. A fuel pump is a device that creates a flow to transmit the fuel from the fuel tank to the fuel rail.

The fuel pump is located in the fuel tank and attached to the fuel gauge sender. The pump has gears or a rotor inside it to create a flow to push the fuel through the fuel lines. The fuel pump usually has a screen on it to keep out the large particles. Most pumps today have filters in them to screen out the small particles.

The fuel pump on an older vehicle before fuel injection was introduced to the automotive industry was attached to the side of engines. These pumps worked like water pikes that pushed up and down to create a flow. There was a rod on the fuel pump that would be pushed down by a cam lobe on the camshaft. It would not matter if the camshaft was out of timing or not.

Some older vehicles would break off the cam lobe on the camshaft causing the fuel pump to fail. Well, a quick fix to get fuel to the fuel management system was to use a 12 volt electric fuel pump. This electronic fuel pump is good, but can create too much flow for the volume of the fuel in the lines.

Fuel pump signs of failure

As the fuel is constantly being filled at the pump, drained by engine operation, and sloshed around due to driving conditions, the Volvo fuel pump constantly heats up and cools down causing the motor to burn slightly. Over time, the motor will have burned enough to cause too much resistance on the electrical contacts. This will make the motor stop working.

When the fuel is low all the time, fuel pumps tend to operate a hotter temperature causing them to burn the contacts up. This will also make the motor stop working.

With the fuel pump working, listen for unusual noises and high-pitched whining noises. This can be a sign of the gears wearing out inside the pump.

When driving the vehicle around during a test drive throttle the engine hard to demand the fuel management system for more fuel. If the fuel pump is working the engine will accelerate quickly; however, if the fuel pump is failing or has failed then the engine will stumble and act as it wants to shut off.

Warning: Do not use starting fluid to start an engine with a failed fuel pump. This will damage the engine.

Other things that happen to cause failure to the fuel pump is the type of fuel is poured into the fuel tank. If fuel was poured in at a gas station while a gas pump truck is fueling the station, junk in the bottom of the large storage tanks will stir up and end up into the fuel tank of the vehicle. The particles can get inside the fuel pump and increase the resistance as the rotor or gears begin to grind.

If the fuel was poured in at a gas station with very little traffic to the station, there may be an excessive amount of water in the fuel causing the fuel pump gears or rotor to rust and cause more strain on the electric motor or get stuck.

Plus, if any of the wiring from the battery or computer to the fuel pump get corroded will cause more resistance than normal making the fuel pump to stop working.

Fuel gauge sender failure on computer controlled vehicles

If the fuel pump fails, the engine management system will record this event. A fuel pressure sensor will let the computer know if the fuel pressure has decreased more than five psi (pounds per square inch).

As the fuel pump is located inside the fuel tank, there is no real way to check it. However, you can check the electronic plug on the fuel pump for any damage. If you have a digital ohm meter, you can check for power at the plug on the harness. You can check for resistance to the motor through the plug on the fuel pump. If there is resistance but not high, then the electric motor should be in good order. If there is no resistance on the fuel pump, then the electric motor contacts have been burned.

Step 1: Check the fuel gauge to see the level. Document the location of the needle or percentage of the fuel level.

Step 2: Start the engine. Listen for any problems within the fuel system. Check to see how long the engine cranks for. Check for any rotten egg smell as the engine is running very lean.

Note: The rotten egg smell is caused by the catalyst becoming too hot due to the emissions burning above the pyrometer temperature.

Part 2 of 9: Prepare to replace the fuel pump

Having all of the necessary tools and materials prior to starting the work will allow you to get the job done more efficiently.