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.
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