Fuel Contamination

Fuel contamination is the main cause of electric fuel pump failure. Dirty fuel, water, rust, scale and fuel tank sediment all work to clog the pickup strainer or inlet filter as well as cause internal pump damage. (Fig. 7) The result is premature pump failure. 

Fig. 7

When replacing a failed fuel pump, check the following to avoid future problems and a repeat failure:

Fuel contamination

Fuel tank degradation

Fuel line corrosion or damage

Blocked inlet strainer

Pump Diagnosis

Before condemning a fuel pump, the first step in fuel pump diagnosis is to perform a fuel pressure check. If the fuel pressure and volume are within specification, use a scan tool to check for diagnostic trouble codes.

If the fuel pressure check reveals improper fuel delivery, too-high or too-low pressure or insufficient flow, there could be a number of possible causes. These include a clogged inlet filter, damaged fuel pump, electrical faults, faulty fuel pressure regulator or fuel line restrictions.

In addition, inspect the terminal in the wiring harness connector and in the connector on the pump module. Any damage to the connectors may result in voltage drop across the module and may lead to a repeat failure.

Checking the Fuel

Once the fuel pump has been diagnosed as the cause of the customer concern, checking the fuel can identify any harmful additives, dirty fuel, or excessive water that could cause pump failure. (Fig. 8) If the inlet filter/strainer is clogging up, the pump's current draw may increase, which could quickly wipe out pump brushes with excess arcing and heat.

Fig. 8

When excessive fuel contamination is evident, remove and thoroughly clean the tank. Tank cleaning procedures vary among models, but general guidelines include: 

Disconnect the negative battery cable.

Relieve the fuel system pressure.

Drain the fuel tank and remove it from the vehicle.

Use oil-free compressed air to blow out fuel lines if needed.

Remove the fuel-sender assembly and inspect for damage.

Fill the fuel tank with hot water. Do this more than once, if necessary.

Pour the flushing water out of the tank through the fuel sender opening.

Ensure that all water is completely removed from the tank before reinstalling.

After cleaning the tank, the fuel and water mixture should be handled as hazardous waste material according to local, state and federal regulations.

Replace the Strainer

The fuel pump inlet strainer filters the fuel to help protect the fuel pump. It's essential that it be replaced and installed correctly when replacing the fuel pump.

On gerotor-type pumps, if the strainer is improperly installed, the gears can scuff and drag, causing noise and vibration. Without a properly functioning strainer, turbine-type pumps will quickly seize up. 

In addition to the strainer, the fuel system can be blocked by a crimp or dent in the fuel line. Any blockage can cause premature fuel pump failure. Also check fuel lines that appear sound externally but may have internal corrosion. Disconnect and inspect any suspect lines.

Fuel pumps do eventually wear out. But sometimes there are other factors that lead to fuel pump failure. It's important to perform a complete diagnosis of the fuel system in order to avoid a replacement pump failing as well. 

- Thanks to Dennis Kissack