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Q: Fuel pressure drops after 30 mins of driving

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Hi goodnight So lets start after driving my car for like 30 mins my fuel pressure drops causing the car to misfire and move slugish I rewired and changed my fuel pump but same issue Im using a tomei fpr,can it be faulty? Can my fpr go bad without leaking fuel from the vaccuum port?

A: The fuel pressure regulator has a vacuum di...

The fuel pressure regulator has a vacuum diaphragm with a spring keeping a certain amount of pressure on the center of the diaphragm to control the amount of fuel returning to the fuel tank ans keeping the correct amount of fuel pressure in the fuel rail. You either have low pressure getting to the regulator or the regulator is stuck open letting too much fuel to return to the tank. You need to block the return line when you have low pressure to see if it is your fuel pump causing the problem. If pressure when return is blocked is well above normal pressure then the regulator is bad. If it is still low then the problem is the pump or power to the pump is less than 12 volts. Some vehicles now control voltage to the pump and may need further diagnosis.

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