Skip the auto shop - Our mechanics make house calls

Q: Why does fuel pressure only read 48 psi CV running on new pum

asked by on

It's a new pump and pressure regulator, but it will go from 48 to 54 psi running. Anything under 50 runs bad. i am a mechanic , can't figure it out.

My car has 200035 miles.
My car has an automatic transmission.

A: One possibility is an internal leak in the ...

One possibility is an internal leak in the system. The leak could occur at an injector or in the tank. Check the fuel pressure with the car off and the key on. Cycle the key a few times to build pressure if you need to. It should not drop more than a few pounds in five minutes with the motor and key off. If it rapidly looses pressure, use a pair of long nose pliers and find a rubber fuel line you can pinch to isolate the fuel tank from the fuel rail. If you pinch off between the tank and the gauge, and it holds pressure, the leak is in the tank. If you pinch off between the gauge and the fuel, and the gauge holds pressure, the leak is in the fuel rail or fuel injector rather.

It is possible the new pump or regulator could be the issue as well. Definitely check for a leak in the system before you decide this though. The pressure are low according to factory specifications. GM vehicles are very sensitive to fuel pressure for sure.

I would also check that you have a good source of power and ground at the pump. I have seen low voltage due to bad connections numerous times. Fuel pump connectors and the connector that is midway down the frame rail will often develop corrosion.

If you should need further assistance, have one of our mobile technicians come to you and help diagnose the issue firsthand. The description of this inspection may not be exact to your symptom, but the diagnosis is the same.

Good luck!

Was this answer helpful?

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・Fair and transparent pricing

Get a quote

What others are asking

Q: how to tell if timing chain is bad

Hello and thank you for contacting YourMechanic. Misfires can be caused by sloppy timing chain, spark plugs and wires not working, injectors not working, or a problem within the engine. To check the timing chain, get a timing light and...

Q: I have a 07 suburban ltz with 150, miles the fuel pump isn't cycling and takes a long time to strt how I check fuel mod wire color

Hello, thank you for writing in. The fuel pump module is protected by a relay, so you are correct in wanting to check the power supply to the unit before replacing it. It should be a full 12 volts. The...

Q: When I take off or reverse the back of my truck makes a cracking noise

You should inspect the rear driveshaft U-joints to see if the joints are bad. You may see where the joints are loose or rust around joints. You will need to replace the U-joints if they are loose or making noise....

Related articles

What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
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...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.