Fuel pump voltage test.
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From: Mobile, Alabama
Fuel pump voltage test.
Can voltage to the fuel pump be read at the output of the cutoff switch to help trouble shoot?
What should it be...........
What should it be...........
Last edited by avproavi; Nov 18, 2011 at 12:53 PM. Reason: more info
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Joined: Jun 2009
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From: Cedar Rapids, IA
Welcome to the forum!
This may be depend on the model year of your truck, possibly even the engine in your truck. Please provide both.
The voltage at the output of the cutoff switch is just that, the voltage at the output of the cutoff switch. There is more wire and more connections between the cutoff switch and the fuel pump, so more opportunities for breaks, corrosion, and other issues. If the wiring is fine between the switch and the fuel pump, then yes, for all practical purposes the voltage out of the switch will be the voltage at the pump.
As for what the voltage should be, that depends on if your particular truck uses a returnless fuel system or not. If it is not a returnless system, then the voltage to the pump should be battery voltage when the engine is running. When the key is turned to Run, the pump should receive battery voltage for a second or two to prime the system.
If the system is a returnless system, then the voltage to the pump will vary depending on the reading from the fuel pressure sensor. The fuel pump driver will use pulse width modulation (PWM) to adjust how much fuel pressure the pump provides to maintain the correct fuel rail pressure.
-Rod
This may be depend on the model year of your truck, possibly even the engine in your truck. Please provide both.
The voltage at the output of the cutoff switch is just that, the voltage at the output of the cutoff switch. There is more wire and more connections between the cutoff switch and the fuel pump, so more opportunities for breaks, corrosion, and other issues. If the wiring is fine between the switch and the fuel pump, then yes, for all practical purposes the voltage out of the switch will be the voltage at the pump.
As for what the voltage should be, that depends on if your particular truck uses a returnless fuel system or not. If it is not a returnless system, then the voltage to the pump should be battery voltage when the engine is running. When the key is turned to Run, the pump should receive battery voltage for a second or two to prime the system.
If the system is a returnless system, then the voltage to the pump will vary depending on the reading from the fuel pressure sensor. The fuel pump driver will use pulse width modulation (PWM) to adjust how much fuel pressure the pump provides to maintain the correct fuel rail pressure.
-Rod
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