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.
Actually, fuel system testing, has already started. When this humming sound is heard, it can usually be assumed that; the fuel pump electrical circuit, is functioning and that, the fuel pump is running.
The next diagnostic steps should include:
- Is there is an adequate amount of fuel in the fuel tank.
- 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:
- 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.
- In contrast, on a 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.
Finally, most conventional fuel delivery systems include, a Schrader valve, at the fuel injector rail. Furthermore, allowing for, mechanical fuel pressure testing.
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