Q: Fuel pressure drops after 30 mins of driving

asked by on

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.

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Stabilitrakservice light is in with traction control light

The stabilitrak and traction control systems may become inactive if the engine light is on. The code for a cylinder misfire on cylinder #7 may be due to the engine oil system containing sludge from improper oil change intervals. This...

Q: Truck won't start

Hi, thanks for writing in. If the truck is getting the correct fuel pressure to the fuel rail, but does not deliver fuel to the spark plugs, this may suggest a fuel injector problem. I would start with checking the...

Q: engine misfire. 1995 Toyota Corolla

Hello. These types of issues can be hard to diagnose. Most of the time they are caused by a failure within the distributor itself. Also common is the shaft being slightly worn, which will cause the RPM reading to be...

Related articles

How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...