Fuel Pump:
The fuel pump is basically an electric motor; fuel is drawn in from the inlet by the roller cell and expelled under high pressure. Although sparks are generated by the brushes rubbing on the commutator, an explosion cannot occur because the Armature is completely immersed in fuel and no air is available.Fuel pumps are a sealed unit and must be replaced if they are worn out or leak.
Fuel Filter
All EFI fuel filters are made of mild steel or aluminium to withstand the high pressure.
They must be replaced at regular intervals, usually 60000 Km, to filter the fuel and to avoid engine power loss due to the paper deteriorating and restricting the flow.The fuel system must be depressurised before the fuel filter can be replaced.
1. While the engine is idling, disable the fuel pump by removing the fuse, relay or connector.2. Crank the engine a few more times until the residual fuel has been used.
3. Remove the fuel filler cap to release pressure in the tank.
4. The fuel filter can now be removed. Take care to use a rag to soak up any fuel that will leak out.
5. Make sure that the new filter is installed correctly. They either have an arrow indicating the direction of flow or are labelled in or out.
Fuel Pressure Regulators:Although the fuel pump is capable of producing 80 psi of pressure, the pressure regulator regulates the pressure between 32-36 psi in the fuel rail.Excess fuel is recycled to the tank while the engine/fuel pump is running via the return line. An undesirable side effect is that the fuel is heated.
At idle, the vacuum is approx. 20"Hg, the fuel pressure is approx. 32 psi. At WOT the vacuum drops to 0" Hg, the fuel pressure then increases to approximately 38. psi.
Make: Toyota 2001
Model: Corolla 4A-FE
Fuel Pressure Specifications
38-44 psi
Measure Fuel Pressure Key On Engine Off:
35 psi
Measure with engine idling
39 psi
Measure Fuel Pressure when hose is clamped
65 psi
With the engine idling, disconnect and plug the vacuum line going to the regulator. Measure the fuel pressure
48 psi
Turn off the engine, and watch the fuel pressure for 5 minutes. Record residual pressure
34 psi
Why is it important to know a vehicles fuel pressure/flow?
It's important to know a vehicles fuel pressure and flow because if your car may be running far too rich if the pressure was too high. You would also have bad emissions and poor fuel economy. It is also good to know so you can achieve the best combustion ratio for the vehicle.
What would happen to a vehicle with a low fuel pressure?
A vehicle with low fuel pressure will give the Engine a lean mixture, which will result in a lack of power. The car would be hesitant and a misfire could occur
What would happen to a vehicle with low fuel flow?A vehicle with low fuel flow will give the vehicle a lean mixture aswell, due to not enough fuel getting into the combustion chamber. The engine will be hard to start, and poor idle quality.
What would happen to a vehicle with High Fuel pressure?
High Fuel Pressure will make a engine run rich, which would give a vehicle bad emissions. The vehicle could be hard to start due to flooding of the engine.
What would happen to a vehicle if the fuel pressure regulator was faulty?
A faulty fuel pressure regulator will give a high fuel pressure if it's blocked, making the car rich, or give a low fuel pressure if it was stuck open which will give the vehicle a lean mixture.
References: Unitec Blackboard, Google Images, Wikipedia
