What causes fuel pressure to go up and down?

Most problems with fuel pressure, are due to the pressure being too low. Other problems that can cause low fuel pressure include; a kinked fuel inlet line or a clogged fuel filter or strainer. A bad fuel pump in the fuel tank; can also prevent the fuel pressure from reaching the required level.

How does a mechanical fuel pump regulate pressure?

When the camshaft lobe is at top dead center, the plunger has just finished pushing the fuel through the discharge valve. A spring is used to pull the plunger outward creating a lower pressure pulling fuel into the chamber from the inlet valve. These pumps can run between 250 and 1,800 bar (3,625 and 26,000 psi).

Can a mechanical fuel pump put out too much pressure?

The fuel delivery system uses a mechanical fuel pump that provides the lower level of pressure that a carburetor operates on. Using the wrong fuel pump that delivers excess pressure can cause problems ranging from poor performance and lower gas mileage to flooding and carburetor damage.

How much pressure does a fuel pump provide?

The fuel delivery system uses a mechanical fuel pump that provides the lower level of pressure that a carburetor operates on. Fuel pressure to the carburetor will range from 4 psi to 7 psi, with some vehicles using higher pressure.

When do you replace a mechanical fuel pump?

If there is no pressure, or if pressure is less than specifications, replace the pump. Most mechanical fuel pumps have a weep hole on the bottom side of the unit. When the internal diaphragm leaks, fuel escapes through the weep hole to notify the vehicle owner of a malfunction.

What happens if you use the wrong fuel pump?

Using the wrong fuel pump that delivers excess pressure can cause problems ranging from poor performance and lower gas mileage to flooding and carburetor damage. When the pressure is only a little over the required amount, your vehicle may sputter when you first accelerate from a stopped position.

Can a vacuum test a mechanical fuel pump?

Many inexpensive old-school vacuum testers can read mechanical fuel pump pressure just as well as vacuum pressure. To perform this test, you should connect the test gauge to the metal output line using a spare piece of rubber fuel hose and a clamp. Once the connection is sealed, crank the engine over for 20 seconds.