So, fuel system testing, always starts, by just listening.

First, turn the ignition key, to the run position and carefully listen.

Consequently, there should be a slight humming sound, coming from the fuel tank. This humming sound, should continue, for approximately 2 seconds before stopping.

As a result, fuel system testing, has already started. Because, when this humming sound is heard, it can usually be assumed, that the fuel pump electrical circuit, is working. And, that the fuel pump is actually running.

So, the next diagnostic steps, should include:

  • Is there enough fuel in the fuel tank?
  • And, testing for fuel pressure and volume.

But, if the humming sound was not heard, then the next fuel system testing steps, should include:

  • Verifying the lack of any fuel pressure, with a fuel gauge or scan tool.
  • Checking the fuel pump electrical circuit.

Fuel System Testing, Common Fuel Delivery Systems

So, the (PCM) commands the fuel pump, to apply 35-65 psi of fuel pressure to the injectors. Consequently, by grounding the primary fuel pump relay circuit.

One And Two Line Fuel Delivery Systems:

So, on single line fuel delivery systems.

So, an internal non-modulated fuel pressure regulator, in the fuel pump module, controls the fuel pressure. But, the single line fuel delivery system, uses the same line.

However, on two line fuel delivery systems.

So, an external vacuum-modulated fuel pressure regulator, controls the fuel pressure. Consequently, The two line fuel delivery system, returns excess fuel to the tank using a return line.

Finally, most conventional fuel delivery systems include, a Schrader valve, at the fuel injector rail. Furthermore, allowing for, mechanical fuel pressure testing.

Choose Your Fuel System Testing Help Topic Below

Fuel Pump Failure – The Most Common Causes And Symptoms

Fuel Pump Related No Start Problems – What Should You Check

Automatic Shutdown (ASD) Relay – Function – Failure – Testing

Fuel Pump Issues – Excessive Heat – Contamination, Dirt, Rust

Noid Light – Tests For An Electrical Signal, At The Fuel Injector

Fuel Wash – What is it – Check If You Have It – Common Causes

Fuel Injectors – Usually Only Fail, In One Of Three Different Ways

Mechanical Fuel Pumps – Basic Information And Troubleshooting

Fuel Injector – Deposits Can Build Up And Clog The Fuel Injector

Fuel Pressure Regulator – Do You Have The Correct Fuel Pressure

Electric Fuel Pumps – How Do They Work – How Can They Fail

Fuel Pressure Regulators – Function, Failure Symptoms And Testing

Fuel Pump Relay – Function – Failure – Testing Procedures

Thank You !