WS4 Fuel Pressure and Flow

Make: Toyota 4A-FE
Warning, be careful around raw fuel. It can catch fire! Use appropriate safety precautions.
Keep sparks, flame, your body and your clothing away from raw fuel! Know where your fire
extinguishers are and use them if necessary.

1. Locate the two closest fire extinguishers. (If you have to use it remember to pull the pin, squeeze the handle, and spray at the base of the flame.) Write down where they are:

Close to exit door.

2. If you can, look up Fuel Pressure specifications for the vehicle you are testing. If you can’t look them up, make a guess at the fuel specs you should have and write them down here:

265-304kPa.

3. Use eye protection. Optional: Relieve fuel pressure before installing pressure gauge. Or there will be some fuel that sprays at you as you attach the gauge. You can relieve pressure by several methods: 
1) To relieve the fuel pressure. Make sure you have a rag to catch the fuel, start the engine.
2) Remove fuel pump (circuit opening) relay or fuse and run the engine until it stops, then crank to check that the engine doesn’t start.
3) Use a vacuum gauge on the pressure regulator to lower fuel pressure, or
4) Open a fuel line at some pressure point and catch the fuel in a rag beware there may be lots of fuel.

4. Attach fuel pressure gauge and notice which scale on the gauge you will be using.
Briefly turn key on or start vehicle, then turn it off. Check for fuel leaks.
Are there leaks? No.
If there are leaks you must correct them and retest before continuing. If you need help, ask !

5. Measure the fuel pressure with the key on, engine off.
Record it here: 44Psi.

6. Idling: Measure the fuel pressure with the engine idling. Watch the pressure for a couple of minutes. Record pressure here: 40Psi.

7. Maximum: With the engine idling, use the special tool to clamp the fuel return line.
Note: this can only be done for a short period.

Record pressure here: 85-87Psi

8. WOT: With the engine idling, disconnect and plug the vacuum line going to the fuel pressure regulator.

Record pressure here:48Psi.

9. Residual: Turn off the engine, and watch the fuel pressure for five minutes.
Record your residual or rest pressure here: 44Psi.

10. Replace vacuum lines. Carefully remove the fuel pressure gauge (beware of fuel spraying into eyes, avoid sparks, etc.) Turn engine key on and off, check for leaks.
Start engine, check for leaks. No leaks.
Replace cap over fuel pressure test port. Check when done: OK.
Make sure the vehicle is safe and runs fine when done, or tell your instructor.

11. Explain why it is important to know a vehicle fuel pressure/flow?

Because flow fuel pressure is decided the engine running rich or lean. How much fuel coming into combustion engine and effect to engine performance.The important thing for environment  decide good or bad for emission. 

13. Describe the symptoms a vehicle would give with each case

Flow of fuel depends on the pressure, if pressure going low automatically fuel is flowing low too. Because the fuel need pressures to flow to combustion chamber. If the fuel pressure to low, less spraying engine will run lean all the time and not performance at all. Specially when idling, the engine turn off easily because not enough fuel and too much air in the combustion. 

High fuel pressure because the fuel regulator is faulty. The faulty of regulator will be causing too much pressure and too much spraying  in the combustion than ECU needs. The car will be running rich. And the car will too much black smog because the unburnt fuel and effect to the electrode of spark plug getting bold easily and worn. One more thing the engine difficult to start early in the morning in case cold condition because too much fuel coming into combustion.

Every manufacturing, they've already program in ECU of how much fuel amount of all the condition and situation. And ECU works depend on all the sensors.    


Faulty fuel pressure regulator will cause high fuel pressure.