How To Diagnose A Failing Fuel Pump

The fuel pump is what sends gas from the fuel tank to the engine. Its failure will mean an unplanned stop by the roadside. There are many warning signs before this happens, though. If you suspect that your fuel pump is failing, then you should get it checked as soon as possible. This guide will explain the steps you should take.

Symptoms To Look For

If the fuel pump is failing, your engine may see an interrupted or intermittent supply of fuel. Or, the fuel pressure may be too low. Any of these situations will cause the engine to run poorly. If you are noticing any of the symptoms listed below, then it may be time to get your fuel pump replaced.

Difficult Starting: If your engine takes several attempts to start, the pump may not be delivering enough fuel.

No Power When Accelerating: Sometimes a failing fuel pump will operate fine under low loads but won’t deliver enough fuel when you accelerate hard.

Random Stalling: If the car cuts out at traffic lights or hesitates under acceleration, the fuel pressure may be dropping intermittently.

Noises From The Gas Tank: The fuel pump is in the fuel tank. If you hear odd whirring or whining noises emanating from that area it is a good bet that the pump is on its last legs.

The Methodical Approach

If you do experience the symptoms above, you'll want to start some troubleshooting so you can determine for sure that the problem is the fuel pump. The diagnostic tests below will get you started. Tools to have available:

  • Fuel pressure test gauge
  • Voltmeter
  • Screwdrivers and ratchet set 
  • Service manual (to check fuel pump flow and voltage figures)

Replace The Fuel Filter

Contaminated fuel can sometimes lead to a blocked fuel filter. This can have very similar symptoms to those listed above.

You should always replace the fuel filter at the manufacturer’s recommended intervals. It is also a good idea to do so whenever you replace the fuel pump.

Not doing so may send contaminated fuel to the new pump which could damage it again. Also, if the filter is blocked, you may continue to experience the same issues.

Test The Fuel Pump Pressure

If the car is starting but won’t run smoothly, the fuel pressure may be too low. You can connect a fuel pressure gauge to your fuel system (usually placed in a dedicated pressure test port).

Have a helper rev the engine while you can watch the gauge. Compare the pressure results to the service manual to see whether the pump is underperforming.

Test The Fuel Pump Voltage

If your car won’t start at all, the fuel pump may have failed completely.

  • Check all the electrical wiring for corrosion.
  • Inspect the relay for burn marks on its connectors.
  • Check the relevant fuse in the fuse box to see whether it has burned out.

If everything comes up fine, then use a voltmeter to check the voltage between the fuel pump’s terminals. Compare the results to the car’s main battery. If they are too low, then the pump may have worn connectors which can increase resistance levels.

Get The Perfect OEM Replacement Part For Your Toyota

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If all signs point to a faulty fuel pump, find the correct Toyota OEM replacement part at Olathe Toyota Parts Center. Not sure what year, model or trim your Toyota is? Use our handy Vin Decoder to be sure you're getting exactly the parts you need. Olathe Toyota Parts Center has 15 years of online sales experience. We supply parts to customers all over the US from our dealership in Kansas City.

We WILL have what you are looking for. If you ever need some help, then let us assist you through our FREE parts lookup service. All our fuel pumps are OEM parts backed by Toyota’s 12-month unlimited miles warranty.