How is the fuel pressure set in a GM return system?

Fuel Pressure Explained. With a return system, the base pressure is set with the engine off, but the pump running. For a GM, this pressure is usually set to 58psi (factory fuel pressure in the rail). The vacuum/boost referenced regulator will help to change the pressure in the rail based on the pressure in the manifold.

What happens when the fuel return line is blocked?

If the pressure is high, the fuel pressure regulator is bad or the fuel return line is somehow blocked. Don’t worry about low pressure at this point. Start the engine up. The fuel pressure regulator is designed to maintain a constant pressure on the injectors, relative to the intake pressure (or vacuum).

What should the fuel pressure be at idle?

There will be a vacuum at idle and the pressure will drop. If you have a vacuum gauge, you can verify this. For each inHg of vacuum at the manifold, you should see a 0.49 psi drop in fuel pressure. So at 15 inHg of vacuum, you should see about 47.6 psi of fuel pressure.

Why does a returnless fuel pump lower fuel pressure?

This lowers the ultimate output of the injectors. Some returnless systems will actually vary the pump output to emulate a referenced system, or to offer more fuel pressure at higher demands and less fuel pressure at lower demands. Ford fuel systems modulate the pump in an effort to maintain effective fuel pressure at 3 bar.

Once the engine is at an idle, it comes back up to 55 lbs. The fuel pump should maintain a constant 60 lbs of pressure under all conditions of the engine. I was thinking it was a fuel regulator that was causing the extra 5 lbs to dump back into the tank.

What should fuel pressure be in a Chevy?

When I started the engine, the fuel rail pressure dropped to 55 lbs. When I revved the engine, the pressure drops to 50 lbs. Once the engine is at an idle, it comes back up to 55 lbs. The fuel pump should maintain a constant 60 lbs of pressure under all conditions of the engine.

How is the pressure in the common rail controlled?

Common Rail Injection System Pressure Control. Abstract: There are several approaches to control the pressure in the common rail. One early approach method was to supply more fuel than is needed to the common rail and use a pressure control valve to spill the excess fuel back to the fuel tank.

Where does the fuel pressure sensor go on a rail?

When you stick a fuel pressure sensor on the end of a rail, it is reading the pressure inside of the rail. While this number is important, it is only half of the story.

What happens when fuel is spilled at high pressure?

Fuel not needed at high pressure is spilled back to the low pressure circuit. By closing the valve earlier or later, the amount of fuel compressed can be increased or decreased respectively. A poppet-type valve is not pressure balanced (i.e., it is pressure-biased) so that once closed, high pressure generated in the pump helps to seal the valve.

Why is there no pressure on the fuel rail?

If the pressure at the exit side of the fuel filter is normal and yet the pressure on the fuel rail is essentially zero, it’s possible the fuel pressure regulator has failed wide open, essentially preventing sufficient pressure from building.

Can a fuel rail pressure sensor be changed?

The fuel pressure sensor is a weak link in the fuel system and many complain that they have had problems with it. It can give up due to high temperatures. Many are wondering if they need to change the high-pressure rail along with the sensor. The answer is no. Only the sensor is changed and the repair takes less than 15 minutes.

What are the symptoms of a bad fuel pressure regulator?

The symptoms are very noticeable, too. You may notice a very rough idle, rough acceleration, slow acceleration, and vibrations from the engine. There are also many causes of engine misfires. It can be a problem in the spark plug or the ignition coil.

What should fuel pressure be on a TBI fuel injection system?

Fuel Pressure is critical to the operation of a fuel injection system. Always check to insure that you have the proper fuel pressure. Fuel pressure should be a constant 10 – 15 PSI on a TBI fuel injection system and is typically around 12 – 13 psi. Higher pressure than 15 psi indicates that there is an issue with the installation.

What should the fuel pressure reading be on a Chevy Cobalt?

The fuel pressure tester should give you a reading between 50 to 60 PSI. CASE 1: The fuel pressure is within the indicated specification. This is the correct test result and it lets you know that the fuel pump is working correctly in your 2.2L Chevrolet Cobalt.

Why does my cobalt engine not start up?

You need to start by checking to see if it is lacking fuel or spark. Add some fuel directly into the engine to see if it will start. If not then it is spark related. If it does then it is fuel related. Your pressure is not terrible so you might not have firing injectors. It is common for the PCM to fail on this car and cause this.

Why is my Chevy Cobalt fuel pump not working?

Defective fuel pumps usually cause one of two types of problems on your 2.2L Chevrolet Cobalt. For the most part, the fuel pump will simply stop working and the engine will not get any fuel which causes it not to start. In certain cases, the fuel pump will function enough to start the vehicle but the engine will not run optimally.

Where is the Schrader valve on a Chevy Cobalt?

As I mentioned at the beginning of the tutorial what makes testing the fuel pump a breeze, on your 2.2L Chevrolet Cobalt, is the fact that a fuel pressure test gauge can be easily connected to the fuel system. This test port is called the Schrader valve. And the Schrader valve is located on the fuel injector rail.

How much pressure does fitech fuel cell hold?

Using Fitech internal. Reads 0 lbs first attempt after a few days if I turn on Fitech before fuel pumps. Immediately goes to 62 lbs when fuel pumps are turned on. Will hold 60 lbs for a little while after pumps turned off. Not sure how long. Fuel cell, holley 12-1800 inline pump, fitech, return to fuel cell. 62 lbs. constant pressure.

What to do if your fuel filter is clogged?

the fuel filter is not clogged (consult your car owner’s manual or repair manual for the service schedule), the fuel injectors are not clogged. First make sure the fuel pump is working. Momentarily remove the fuel filler cap. Ask an assistant to turn the ignition key to the On position, but don’t start the engine.

What can I do to relieve the pressure in the fuel tank?

Warning. Always loosen or remove the fuel filler cap on your vehicle when you are working on the fuel tank. That will relieve pressure build-up in the tank. Always disconnect the negative battery cable when working the fuel system of a car.

When do you have to pressurize the fuel system?

After you have completed a repair such as changing the fuel pump or changing the fuel filter you will have to re-pressurize the car’s fuel system. If you have just diagnosed a no-start by releasing the schrader valve in the fuel line, you may also have to re-pressurize the fuel system.

How does a fuel pressure regulator work on a car?

When autocomplete results are available use up and down arrows to review and enter to select. Touch device users, explore by touch or with swipe gestures. A fuel pressure regulator helps provide constant fuel supply while driving. In fuel injection systems, it is used to build up pressure to supply the injectors with fuel.

How does the bypass work in fuel injection?

Any bypass jets (including the main bypass, high-speed bypass, pump saver or others) divert excess fuel away from these engine nozzles to maintain a proper air to fuel ratio. Most fuel injection systems have a main bypass circuit.

What should fuel pressure be on a Cummins PT pump?

2. Connect a pressure gauge to the quick disconnect fitting of the fuel pump. Start cranking the engine and observe the cranking fuel pressure. Minimum cranking pressure should be 25psi. 3. If the fuel pressure is below the specification, check to be sure there is a fuel supply to the pump and that it is not restricted.

What should the fuel pressure be at the fuel rail?

Fuel Pressure: What Should the Fuel Pressure Be at the Fuel Rail What should the fuel pressure be at the fuel rail of a ranger with the 2.3 liter engine? have the same problem? Please let us know if you need anything else to get the problem fixed. helpful?

What should fuel pressure be in a 1994 Ford F150?

1994 Ford F150 5.0 Vehicle runs great, starts fine on cold start, but if you drive for awhile, it has a long start issue. Ideas? Submitted:8 years ago.

What should my fuel pressure reading be on my car?

A car with a port-injected pump should yield a reading between 30 and 80 PSI. If it does not match the required pressure, you should take the car to a servicing shop for maintenance and pump replacement.

What to do when your fuel pressure is low?

There are a lot of different causes of low fuel pressure, but here you will find the most common solutions to fix your low fuel pressure. The first thing you can do is to check the screen filter. The screen filter protects the fuel pump from dust and debris and can get clogged up pretty quickly.

How does the fuel pressure regulator ( FPR ) work?

Further, reducing the pressure by 10 PSI. This then gives you your desired fuel pressure of 40 PSI. At a boost pressure of 10 PSI, the nozzle is exposed to 10 PSI of pressure. This pressure is acting against the base fuel pressure.

What should fuel pressure be in a car?

Holds pressure around 52psi. Turn key off and pressure drops rapidly. When motor hot, turn key on and climbs slowly mid 50s, then falls back down. Long crank and need to pump pedal to catch. Once going, pressure fluctuates crazily between 48-53psi. Turn off, then drops off rapidly.

How can I tell if my fuel pressure sensor is correct?

First, make sure that the fuel pressure sensor is correct. Check the fuel pressure with a manual fuel pressure gauge to figure out if you can find any problems with the pressure. If so check fuel pressure regulator.

How is the fuel pressure set in a GM return system?