Make....Toyota.....
Model..4A-FE...
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? Yes .................... No ..no leaks..........
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: ........284kpa................. (also record the units you are using, psi, bar,
Kpa, etc…)
6. Idling: Measure the fuel pressure with the engine idling. Watch the pressure for a
couple of minutes.
Record pressure here: .........260kpa..........................
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:………490kpa…………….
8. WOT: With the engine idling, disconnect and plug the vacuum line going to the fuel
pressure regulator.
Record pressure here: ...........310kpa........................
9. Residual: Turn off the engine, and watch the fuel pressure for five minutes.
Record your residual or rest pressure here: .........259kpa.............................
10. Flow:To check the folw of fuel in the fuel lines and to make sure enough fuel is getting to our injectors 2.2 L per minute and also to check if it is within manufacture's specification because too low will cause a lean combustion and too much will make it run rich.
The importance of knowing the vehicle fuel pressure is because low or high pressure may effect the engine performance. High pressure pushes more fuel in the injectors and makes the engine run rich and low pressure makes it run lean and also tests faulty pressure regulator and whether the fuel pump is working or not and what the pressure of the fuel pump is.
Describe the symptoms a vehicle would give with each case:Low fuel pressure: The engine will run lean and the oxygen sensor will give send the signal to ECU to reduce the amount of air so makes the throttle more close even there is high demand of air for engine performance
Low fuel flow: The engine will run lean and the oxygen sensor will send the signal to ECU to reduce the amount of air making the throttle closer even though there is high demand of air for engine performance.
High fuel pressure: High pressure puts more fuel in the injector making engine runs rich and so the oxygen sensor will sense that there is a shortage of air and will send the signal to ECU to send more air in and hence effect the engine performance.
Faulty fuel pressure regulator: Faulty regualtor extra fuel will not return to the tank causing the fuel to pass through the injectors engine, high HC coming out form the exhauct .With the engine idling, use the special tool to clamp the fuel return line.
Low fuel flow: The engine will run lean and the oxygen sensor will send the signal to ECU to reduce the amount of air making the throttle closer even though there is high demand of air for engine performance.
High fuel pressure: High pressure puts more fuel in the injector making engine runs rich and so the oxygen sensor will sense that there is a shortage of air and will send the signal to ECU to send more air in and hence effect the engine performance.
Faulty fuel pressure regulator: Faulty regualtor extra fuel will not return to the tank causing the fuel to pass through the injectors engine, high HC coming out form the exhauct .With the engine idling, use the special tool to clamp the fuel return line.
The ECU can't control the amount of air going in to the engine it controls the amount of fuel and this depends on load,speed and throttle opening
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