WS4 Fuel Pressure and flow (Petrol only)

Make Toyota       Model 4A FE

its important to know a vehicles fuel pressure/flow because if your vehicles fuel pressure is to low there could be a leak somewhere or fuel pump could be faultyor need to replace fuel filter. Or if your fuel pressure is to high there could be faulty fuel pressure regulator or blocked return line this will make the vehicle use a lot of petrol.

Describe the symptoms a vehicle would give with each case.

Low fuel pressure - vehicles may surge, stall, engine hesitation wile accelerating, lack power.

Low fuel flow - engine wont start, abnormal engine combustion, surging.

High fuel pressure - high CO emissions, hard starting , poor fuel economy

Faulty fuel pressure regulator - excessive fuel pressure, engine running rich, bad fuel economy

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:

Its located by the garage 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:

265-304 kp ( 2.7 - 3.1 kgf/cm , 38 - 44 ps

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: 300 kpa  (also record the units you are using, psi, bar,
Kpa, etc…)43 psi

also a fuel trim is a the fine tune control of fuel delivering by the ECU

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

Record pressure here:780kpa

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:600 kpa

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

          Record pressure here:340 kpa

9.         Residual: Turn off the engine, and watch the fuel pressure for five minutes.

Record your residual or rest pressure here: 300kpa no drop 

10.      Flow: Hook up proper equipment to read fuel volume if necessary. Record flow gauge results of volume, or how much pumped in 15 seconds: (normal results may be ½ liter in 15 seconds)

NA

11.      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? Check here: NO LEAKS

Replace cap over fuel pressure test port. Check when done: CHECKD

Make sure the vehicle is safe and runs fine when done, or tell your instructor.

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

Fuel pressure make injector spraying pressure, If it doen't have enough pressure, the fuel is not supply to cylinder.

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

Low fuel pressure

it will run lean it wont idle propelley and also the RPM will be low and will be running rough

Low fuel flow

it could be caused by blocked fuel filter which means weak return valve in fuel pump

spring cam gets weaker it will be always richer means it will be using a lot of petrol.

High fuel pressure

Too much fuel being used and there will be dripping injectors meaning there will be 

flooding and also return regulator will be break.

Faulty fuel pressure regulator

Fuel pressure regulators do not fail often to work properly. However, if they do fail, then it may result in low pressure. Mostly the diaphragm in the fuel pressure regulator develops a leakage and the fuel enters the vacuum hose. This may lead to various kinds of troubles in the engine. 

flooding of injectors which will leak out the injectors and causes hard start

also alot petrol will be used and fuel will leak into the intake manifold and cause rich condition

affection fuel millage and hot engine starts 

it will be much like an applied choke on a carbonated engine( aiding cold start and hindering hot starts.